Neuropsychological Outcome Following Cranio-spinal Radiation in Medulloblastoma Patients: a Longitudinal Analysis of Predictors

Transcription

1 Neuropsychological Outcome Following Cranio-spinal Radiation in Medulloblastoma Patients: a Longitudinal Analysis of Predictors by Iska Moxon-Emre A thesis submitted in conformity with the requirements for the degree of Master of Arts Department of Psychology University of Toronto Copyright by Iska Moxon-Emre 2013

2 Neuropsychological Outcome Following Cranio-spinal Radiation in Medulloblastoma Patients: a Longitudinal Analysis of Predictors Abstract Iska Moxon-Emre Master of Arts Department of Psychology University of Toronto 2013 Medulloblastoma is the most common malignant central nervous system (CNS) tumor in childhood. The cranio-spinal radiation (CSR) required to treat this disease results in long-term cognitive and neurologic impairments. Medulloblastoma was recently categorized into four genetic subgroups (WNT, SHH, Group 3, and Group 4). This study examined neuropsychological and intellectual functioning in 91 medulloblastoma patients (41 Group 4; 20 Group 3; 18 SHH; 12 WNT) following treatment, and examined the impact of several medical, treatment and demographic factors on functioning over time. Longitudinal growth curve analyses revealed hydrocephalus most clearly predisposes to poor neuropsychological functioning. Results also indicate medulloblastoma subgroups have heterogeneous intellectual outcomes following treatment. All subgroups experience intellectual declines following treatment; however, comparing between subgroups revealed Group 4 performs most poorly, and Group 3 has the best overall intellectual outcome. Lastly, qualitative analyses suggest treatment with a larger CSR dose may contribute to poor intellectual functioning. ii

3 Acknowledgments The work presented in this thesis would not have been possible without the support from several remarkable individuals. The unusual circumstances under which this thesis was written highlighted the importance of having a supportive supervisor and colleagues, and I could not have been luckier in this regard. I would like to thank my supervisor, Dr. Donald Mabbott, for believing in my ability to successfully complete a 1-year program in a single semester. Don s flexibility and support was truly outstanding, and I feel very fortunate to be embarking on my PhD under his supervision. I would also like to thank my subsidiary advisor, Dr. Mary Lou Smith, for playing a key role in permitting me to pursue this degree in a shortened time period, and for providing helpful comments to this work. I would like to thank Dr. Michael Taylor for acting as my examiner, and for providing useful edits to this thesis. I would also like to thank SickKids for providing me with financial support through the Restracomp MA award. This difficult time was made far more bearable because of all the members of lab, Nicole Law, Nadia Scantlebury, Melanie Orfus, Frank Wang, Lily Riggs, Fang Liu, Naomi Smith and Colleen Dockstader, who consistently showered me with encouragement and offered to help every step along the way. I feel truly lucky to work with such a warm and supportive group of individuals. And last but not least, I would like to thank my family, friends and James, who provided me with tremendous love and support through this intensely challenging time. iii

4 Table of Contents Acknowledgments... iii Table of Contents... iv List of Tables... vii List of Figures... viii List of Appendices... ix List of Supplementary Tables... x Chapter Overview Aim Aim Aim Introduction Brain Tumors Medulloblastoma development Medulloblastoma subgroups Medulloblastoma treatment Neuropsychological late effects of medulloblastoma treatment Age at diagnosis Tumor location Post-Surgical/Medical Complications Chemotherapy Cranio-spinal radiation Recent advances and moving forward Patients and Methods iv

5 3.1 Patient information Materials and Procedures Intelligence Academic Performance Receptive Vocabulary Visual Motor Integration Fine Motor Skills Memory Attention Assessments Medical Variables Subgrouping Medulloblastoma Statistical Analysis Aim Aim Aim Results Aim Aim 1a: Neuropsychological outcome in all medulloblastoma patients Aim 1b: Intellectual outcome as a function of demographic, medical and treatment variables Aim 2: Intellectual Outcome as a Function of Medulloblastoma Subgroup Aim 3: Intellectual outcome as a function of treatment intensity in Group 4 patients Discussion Hydrocephalus Medulloblastoma Subgroups v

6 5.2.1 WNT Group Group SHH Treatment Intensity (CSR dose and boost field) All medulloblastoma patients Group Limitations Future directions All medulloblastoma patents Subgroups Conclusion References Appendices Supplementary Tables vi

7 List of Tables Table 1: Clinical profiles of the most common pediatric brain tumor types....5 Table 2: Demographic profiles of medulloblastoma subgroups... 9 Table 3: Indexed scores considered equivalent across different test types and versions Table 4: Number of observations for the different test types in each assessment year..21 Table 5: Neuropsychological assessments...22 Table 6: Therapeutic agents used in chemotherapy protocols...24 Table 7: Nanostring CodeSet...26 Table 8: Estimated intercepts and slopes for measures of neuropsychological functioning in all medulloblastoma patients...31 Table 9: Group means, overall group and mean slope differences for neuropsychological measures in medulloblastoma patients stratified by the presence/absence of hydrocephalus Table 10: Estimated intercepts and slopes for measures of neuropsychological functioning in medulloblastoma patients stratified by the presence/absence of hydrocephalus...33 Table 11: Group means and standard error for measures of intelligence in each subgroup.37 Table 12: Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by subgroup vii

8 List of Figures Figure 1. Patient Characteristics..17 Figure 2. Medical Variables.25 Figure 3. Observed and estimated declines in FSIQ scores over time for patients with and without hydrocephalus...32 Figure 4. Observed declines in PRI and WMI scores in patients that received a TB boost treated with standard vs. reduced dose CSR Figure 5. Observed decline in FSIQ scores over time for patients within each subgroup...36 Figure 6. Observed and estimated declines in PRI scores over time for patients in Group 4 and SHH.38 Figure 7. Observed and estimated declines in PSI scores over time for patients in Group 4, Group 3 and SHH..39 Figure 8. Observed and estimated declines in WMI scores over time for patients in Group 3 and SHH.39 viii

9 List of Appendices Appendix 1. Detailed medical information for Group 4 patients.62 Appendix 2. Detailed medical information for Group 3, SHH and WNT patients..63 ix

10 List of Supplementary Tables Table 1. Group means, overall group and mean slope differences for measures of intellectual functioning in medulloblastoma patients stratified by age at diagnosis Table 2. Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by age at diagnosis...65 Table 3. Group means, overall group and mean slope differences for measures of intellectual functioning in medulloblastoma patients stratified by extent of tumor resection..65 Table 4. Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by extent of tumor resection 66 Table 5. Group means, overall group and mean slope differences for CMS memory measures in medulloblastoma patients stratified by the presence/absence of hydrocephalus...66 Table 6. Estimated intercepts and slopes for CMS memory measures in medulloblastoma patients stratified by the presence/absence of hydrocephalus Table 7. Group means, overall group and mean slope differences for measures of intellectual functioning in medulloblastoma patients stratified by clinical risk Table 8. Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by clinical risk..68 Table 9. Group means, overall group and mean slope differences for measures of intellectual functioning in medulloblastoma patients stratified by CSR dose...68 Table 10. Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by CSR dose Table 11. Group means, overall group and mean slope differences for measures of intellectual functioning in patients that received a PF boost stratified by CSR dose...69 Table 12. Estimated intercepts and slopes for measures of intellectual functioning in patients that received a PF boost stratified by CSR dose..69 x

11 Table 13. Group means, overall group and mean slope differences for measures of intellectual functioning in patients that received a TB boost stratified by CSR dose...69 Table 14. Estimated intercepts and slopes for measures of intellectual functioning in patients that received a TB boost stratified by CSR dose.70 Table 15. Overall group and mean slope differences for measures of intellectual functioning in patients stratified by medulloblastoma subgroup..70 Table 16. Group means, overall group and mean slope differences for measures of intellectual functioning in Group 4 patients stratified by CSR dose Table 17. Estimated intercepts and slopes for measures of intellectual functioning in Group 4 patients stratified by CSR dose Table 18. Group means, overall group and mean slope differences for measures of intellectual functioning in Group 4 patients that received a PF boost stratified by CSR dose..71 Table 19. Estimated intercepts and slopes for measures of intellectual functioning in Group 4 patients that received a PF boost stratified by CSR dose...72 Table 20. Group means, overall group and mean slope differences for measures of intellectual functioning in Group 4 patients that received a TB boost stratified by CSR dose.. 72 Table 21. Estimated intercepts and slopes for measures of intellectual functioning in Group 4 patients that received a TB boost stratified by CSR dose..73 xi

12 1 1 Overview Chapter 1 Brain tumors are the most common solid tumors in childhood, and are the leading cause of childhood cancer-related mortality and disability (Pollack and Jakacki, 2011). The treatments required for effective tumor control often result in long-term physical, endocrine and neuropsychological impairments that dramatically impact survivors quality of life. Worldwide population-based surveys of childhood brain tumors reveal yearly incidence rates ranging from per million of the child population (Makino et al., 2010). More than half the diagnosed central nervous system (CNS) tumors in children are located in the posterior fossa (PF), a brain region that encompasses the cerebellum and brainstem (Poretti et al., 2012). The most prevalent childhood brain tumor types are medulloblastoma, ependymoma and gliomas, with medulloblastomas being the most common malignant CNS tumors in childhood (Dubuc et al., 2010). A recent study demonstrated only 30% of all medulloblastoma patients who survived more than 10 years were capable of living independently as a result of physical and cognitive morbidities (Maddrey et al., 2005). The severity and debilitating nature of these long-term sequalae have necessitated that treatment protocols be adjusted, with the goal being to reduce negative effects of treatment while maintaining current cure rates. In order for this to be achieved, further characterization of medulloblastoma pathobiology is required. Medulloblastoma was considered a single disease until recently, when RNA profiling on expression microarrays revealed the existence of four discrete molecular variants of medulloblastoma; WNT, SHH, Group 3 and Group 4. These four subgroups have distinct demographics, histology, gene expression, transcriptional and clinical profiles that appear to shape their biological behavior and response to treatment (Ellison et al., 2011, Northcott et al., 2011, Taylor et al., 2012). The exact number of subtypes within each subgroup is still unknown, but it is expected more than one exists for each subgroup (Taylor et al., 2012). Treatment of medulloblastoma has remained largely homogenous for the past several decades and includes surgery, cranial-spinal radiation (CSR), and chemotherapy. However, the recent discovery of

13 2 medulloblastoma subgroups has led the medical community to contemplate transitioning towards subgroup-specific treatment of this disease where therapy would be tailored to the particular characteristics of each subgroup (ISPNO conference, 2012). In doing so, the intent is to prevent some of the physical, endocrine and neuropsychological impairments that result from treatment for medulloblastoma by reducing treatment intensity for subgroups that have less aggressive tumors and better survival profiles. In light of this pending treatment shift, it is necessary for each subgroup to be characterized as comprehensively as possible. Tremendous work has been done to characterize the genetic, demographic and clinical features of individual subgroups (Taylor et al., 2012), but neuropsychological outcomes of individual subgroups have yet to be examined. However, before outcomes are examined in a subgroup-specific manner, it is important to clearly establish the factors that contribute to poor neuropsychological outcome in medulloblastoma patients as a whole. To this end, this thesis seeks to characterize neuropsychological outcome following CSR in medulloblastoma patients and is organized into 3 specific aims: First, neuropsychological outcome will be examined in medulloblastoma patients as a whole. Second, potential differences in intellectual outcome between the four subgroups will be evaluated. Finally, differences in intellectual outcome will be examined as a function of treatment intensity (CSR dose and boost field) in Group 4 patients only. Group 4 is the only subgroup with which we have adequate power in our sample to address questions of treatment intensity. 1.1 Aim 1 It is well established that treatment with CSR following the surgical resection of medulloblastoma results in a decline in neuropsychological functioning over time (Kieffer- Renaux et al., 2000, Ris et al., 2001, Palmer et al., 2003, Spiegler et al., 2004, Mabbott et al., 2005, Mabbott et al., 2008). Although the overall adverse effects of CSR are well documented, there is much less literature focused on the mediating impact of specific treatment and medical factors on neuropsychological outcome. In Aim 1, the impact of treatment intensity (i.e. CSR dose and field), success of surgery (i.e. extent of resection), demographics (i.e. age at diagnosis), medical characteristics (i.e. clinical risk), and medical complications (i.e. hydrocephalus) on

14 3 intellectual outcome will be evaluated. Standardized measures to evaluate intelligence, academic performance, receptive vocabulary, visual motor integration, fine motor skills, memory and attention will be used to characterize neuropsychological functioning in our entire medulloblastoma sample longitudinally from shortly after treatment (i.e., baseline) over several year follow-up. Intellectual outcome in our medulloblastoma sample will then be examined as a function of the abovementioned factors to assess if any predispose to poor outcome following treatment. Only by having a clear understanding of how our entire medulloblastoma sample responds to treatment can we begin evaluating if, how and why the individual subgroups differ. 1.2 Aim 2 Currently it is unknown if patients in each of the four medulloblastoma subgroups experience identical declines following treatment. Medulloblastoma subgroups have been shown to differ considerably in their clinical and demographic profiles, factors that could contribute to better or worse intellectual outcome. Namely, some differences that have emerged between subgroups include age at which the tumor presents, and the proportion of patients with metastatic disease both factors that can affect intellectual outcome. For instance, young children are known to be more vulnerable to the neuropsychological late effects of treatment with CSR (Spiegler et al., 2004, Mabbott et al., 2005, Edelstein et al., 2011); thus, differences in age at diagnosis between subgroups could translate into subgroup-specific differences in intellectual outcome following treatment. Similarly, tumors of certain subgroups are more frequently metastatic than others. A tumor s metastatic status (i.e. clinical risk) plays a large role in determining the aggressiveness of treatment received, and could therefore indirectly impact intellectual outcome. In Aim 2 intellectual functioning following treatment will be examined as a function of medulloblastoma subgroup. Because our medulloblastoma sample will be divided into four for this portion of the analysis, our sample sizes will be too small to consider all measures of neuropsychological functioning in each subgroup, therefore only measures of intelligence will be used. If differences in intellectual functioning are observed between subgroups, and if Aim 1 reveals any demographic, treatment or medical factors that predispose to poor outcome following treatment (termed critical factors for our purposes), wherever possible, it will be examined if differences in intellectual functioning between subgroups can be explained by the differing degree to which these critical factors are represented in each subgroup. In doing so, it will be evaluated, albeit indirectly, if intellectual outcome in the

15 4 different subgroups is dictated by something other than their demographic, treatment and medical features (i.e. their underlying genetics). 1.3 Aim 3 There are known differences in patient survival across medulloblastoma subgroups, the most dramatic of which are between WNT and Group 3; nearly all WNT patients survive while Group 3 patients have very poor prognosis (Taylor et al., 2012). One of the rationales for tailoring therapy to individual subgroups is to preserve neuropsychological functioning by reducing treatment intensity for subgroups that have better survival outcomes. Treatment intensity is currently decided upon by taking the tumour s location, metastatic stage, postoperative residual disease and patient age into consideration (Packer et al., 2003). Therapy de-escalation should, in theory, prevent some of the intellectual morbidity associated with aggressive treatment; however, it is important to establish a clear intellectual cost associated with aggressive treatment in individual subgroups in order for changes in treatment to be justified on this basis. In Aim 3, the intellectual cost associated with more aggressive treatment will be examined by looking at Group 4 patients and by examining intellectual outcome as a function of treatment intensity, both with respect to CSR dose and boost field. Group 4 is the most commonly occurring subgroup, accounting for almost half the diagnosed medulloblastomas and is the only subgroup with which we have adequate power in our sample to address questions of treatment intensity. Evaluating the impact of treatment intensity within a single subgroup ensures we are dealing with a clinically and demographically uniform sample, and as such, will provide important clues about the relative importance of subgroup versus treatment factors in affecting intellectual decline following CSR. The information gleaned from this study will be essential for improving our understanding of long-term neuropsychological outcome in all medulloblastoma patients and intellectual outcome within individual subgroups. It will also provide important information about the factors that have the greatest impact on intellectual decline in medulloblastoma patients following treatment with CSR.

16 5 2 Introduction 2.1 Brain Tumors Brain tumor types differ in their developmental, biological and clinical profiles; thus, methods to predict a tumor s behavior is a subject of ongoing investigation. One well established method of doing so is by assigning it a histological grade. To date, the grade a tumor receives influences the course of treatment a patient receives, and is a key factor in determining if radiation and chemotherapy will be used (Louis et al., 2007). Briefly, grade I tumors have low proliferative potential, and are often cured with surgical resection alone, while Grade II lesions generally have low proliferative activity, but are frequently infiltrative in nature and tend to recur (Louis et al., 2007). Grade III tumors usually display evidence of malignancy, while Grade IV tumors are malignant, mitotically active, necrosis-prone, evolve rapidly, and are often associated with poor outcome (Louis et al., 2007). Patients with grade III and IV tumors typically receive radiation and/or chemotherapy as an adjunct to surgery (Louis et al., 2007). While histological classification remains routine and valuable, recent advances in genomic techniques have resulted in the discovery of tumor-specific molecular characteristics not discernible by histology. Namely, differences in gene mutations, copy number aberrations and deregulation of the transcriptome that contribute to the unique biological development of these tumors are gradually being revealed (Dubuc et al., 2010). The differences in histological grade, tumor location, treatment protocols and prognosis for the most common brain tumor types are described in Table 1. Table 1

17 6 Table 1 - Clinical profiles of the most common pediatric brain tumor types. Data from this table were compiled from: (Louis et al., 2007, Qaddoumi et al., 2009, Pollack and Jakacki, 2011, Wisoff et al., 2011) Most childhood brain tumors are thought to occur sporadically, although some are known to result from genetic cancer predisposition syndromes (Pollack and Jakacki, 2011). Neurofibromatosis 1 (NF1), an inherited disorder characterized by the formation of nerve tissue tumors in the skin, brain and spinal cord, is the most common genetic risk factor (Ullrich, 2008). Other predisposition syndromes identified to date include Li-Fraumeni (LFS), a hereditary disorder associated with a wide range of tumors that present at a young age, including sarcomas, leukemia and breast cancer (Li et al., 1988, Ullrich, 2008). Additional risk factors include tuberous sclerosis, Neurofibromatosis 2, Von Hippel-Lindau disease, Turcot and Gorlin syndromes (Ullrich, 2008). Although less common than NF1, all these syndromes result from germline mutations that increase susceptibility to tumor formation, and each are associated with specific brain tumor types (Ullrich, 2008, Pollack and Jakacki, 2011). Medulloblastomas are grade IV embryonal tumors and can be classified into one of five distinct histological groups: classic, desmoplastic, anaplastic, large cell, and medulloblastoma with extensive nodularity (Gilbertson and Ellison, 2008). Pathological classification is utilized clinically to stratify patients into one of two risk groups, as histological groups correlate with differing degrees of survival. Namely, large cell and anaplastic medulloblastomas have the poorest outcome, while desmoplastic medulloblastomas have the best outcome (Bourdeaut et al., 2011). However, subtyping medulloblastoma by histology alone is not ideal since inconsistencies between pathologists interpretation and difficulties defining subtle features may be confounding factors (Bourdeaut et al., 2011). 2.2 Medulloblastoma development Medulloblastoma is thought to arise from disruptions in normal cerebellar development. Neuronal progenitors with defective gene regulation or harboring abnormalities in genes and proteins responsible for regulating normal cerebellar development are thought to underlie medulloblastoma development (Marino, 2005). The cerebellar cortex is comprised predominately of two neuron types; granule cells and purkinje cells. Purkinje cells arise from the dorsomedial ventricular zone along the 4th ventricle

18 7 of the embryonic cerebellum, while cerebellar granule neurons are generated from the secondary germinal zone that forms along the anterior aspect of the rhombic lip (Hatten and Roussel, 2011). Mature cerebellar granule cells coordinate afferent input and motor output through their excitatory connections with Purkinje cells, the main cerebellar output neuron (Ito, 2006). It is well established that the cerebellum plays a role in sensori-motor functions, balance control, and the vestibular ocular reflex, but several roles in motor learning, speech and spatial memory have been documented as well (Hatten and Roussel, 2011). Furthermore, reciprocal connections between the cerebellum and frontal lobes have been shown to play a role in higher cognitive function (Dum and Strick, 2003). The expression of genes and transcription factors responsible for establishing the cerebellar territory during development are controlled in part by secreted proteins from the WNT family (McMahon and Bradley, 1990). Medulloblastoma cells with activated WNT signalling arise from progenitors in the embryonic dorsal brainstem and lower rhombic lip of the cerebellum (Gibson et al., 2010, Hatten and Roussel, 2011). Interestingly, 10-15% of human medulloblastomas have deregulated WNT signalling, where the pathway remains constitutively activated, and transcription is increased leading to tumor development (Hatten and Roussel, 2011). During development, the production of Sonic hedgehog (SHH) from Purkinje neurons drives proliferation of the granule cerebellar progenitors and this process controls the number of granule cells that enter the cerebellar circuit (Hatten, 1999). SHH binds to a transmembrane receptor called Patched (Ptch) that is found in two forms, Ptch1 and 2 (Hatten, 1999). While medulloblastoma can result from several disruptions along the SHH pathway, many medulloblastomas, including those that develop in patients with Gorlin syndrome, result from mutations in Ptch (Hatten and Roussel, 2011). Medulloblastomas arising from a constitutively activated SHH/Ptch pathway originate from the granule cerebellar progenitors, yet it is currently unknown if medulloblastoma resulting from different alterations along this pathway and others also originate from granule cell precursors or from other cerebellar neurons (Gilbertson and Ellison, 2008). Approximately 40% of desmoplastic medulloblastomas occurring in young children have active SHH signalling (Bourdeaut et al., 2011). Interestingly, several molecular inhibitors of the SHH/Ptch signalling pathway have shown therapeutic promise by successfully suppressing

19 8 medulloblastoma formation in mouse models of medulloblastoma, and some of these compounds have advanced to clinical trials (Hatten and Roussel, 2011). By understanding the disrupted signalling pathways, novel animal models of human medulloblastoma can be developed, and therapeutic molecular targets can be tested. 2.3 Medulloblastoma subgroups The specific gene mutations and aberrations that lead to medulloblastoma development differ considerably between subgroups and are thus characteristic of each subgroup. Notably, a deletion of one copy of chromosome 6 is a common characteristic in WNT medulloblastomas and the deletion of chromosome 9q, which contains the gene PTCH, is limited to SHH tumors (Northcott et al., 2011, Taylor et al., 2012). Interestingly, some of the subgroup-specific genetic abnormalities are related to genetic cancer predisposition syndromes. Namely, WNT tumors occasionally harbor germline mutations in the WNT pathway inhibitor adenomatous polyposis coli (APC), a phenomenon that predisposes to Turcot syndrome (Hamilton et al., 1995, Taylor et al., 2012). Additionally, SHH tumors occasionally harbor germline mutations in the SHH receptor PTCH, a feature characteristic of Gorlin syndrome (Bale et al., 1998, Taylor et al., 2012). As previously mentioned, there are reported subgroup specific differences in the location of tumor development, with WNT tumors developing from the dorsal brainstem and SHH tumors developing from granule neuron precursor cells of the cerebellum (Gibson et al., 2010). To date, most genetic alterations documented in Group 3 and Group 4 medulloblastomas are not entirely subgroup specific. Namely, high levels of the regulator gene MYC have been documented in Group 3 medulloblastoma, but also occur in the WNT subgroup (Hatten and Roussel, 2011, Northcott et al., 2011). Furthermore, amplification and over expression of OTX2, while characteristic of Group 3 medulloblastoma, is also common in Group 4 (Di et al., 2005, Taylor et al., 2012). Group 3 tumors overexpress several genes that were initially identified through their role in retinal development, but this relationship is not yet clearly understood (Cho et al., 2011, Northcott et al., 2011, Kool et al., 2012). The most common cytogenic change in Group 4, affecting 66% of patients, is found on chromosome 17q, a phenomenon that affects 26% of Group 3 tumors as well (Taylor et al., 2012). Several reports have documented the over-expression of genes involved in neuronal differentiation and neuronal development in Group 3 tumors, but the importance of this is currently unknown (Cho et al., 2011, Northcott et al., 2011, Kool et al., 2012).

20 9 Thus, WNT and SHH medulloblastoma are named after the signaling pathways believed to play a role in their pathogenesis, while Group 3 and Group 4 have retained generic names because their underlying biology have yet to be clearly established (Taylor et al., 2012). In addition to differences in tumor biology, medulloblastoma subgroups have distinct clinical profiles. Namely, there are considerable differences among subgroups with respect to prevalence, male to female ratios, and age at diagnosis. These differences are summarized in Table 2. Table 2 Demographic profiles of medulloblastoma subgroups. Data from this table were compiled from: (Peris-Bonet et al., 2006, Northcott et al., 2011, Kool et al., 2012, O'Halloran et al., 2012, Taylor et al., 2012) There are also considerable inter-subgroup differences regarding the presence and degree of metastasis. A tumor is defined as metastatic when it has acquired genetic alterations that allow it to transcend physical boundaries, spread, and colonize distant tissues (Chiang and Massague, 2008). Metastasis is rare in WNT medulloblastomas, but the frequency increases progressively for SHH, Group 4 and Group 3 medulloblastomas subgroups alike, with Group 3 tumors being most frequently metastatic (Cho et al., 2011, Northcott et al., 2011).

21 10 While the overall survival rate for children with medulloblastoma has increased considerably over the past two decades, the disparity in survival rates between subgroups is striking. Compared with other subgroups, patients with WNT medulloblastoma have an excellent long-term prognosis; survival rates exceed 90% (Ellison et al., 2011, Northcott et al., 2011). In stark contrast, patients with Group 3 medulloblastoma have a poor long-term prognosis regardless of metastatic status; a recent study by Northcott and colleagues demonstrated a consistent decline in survival that neared zero by 8 years post-diagnosis (Northcott et al., 2011). Patients with Group 4 and SHH medulloblastomas have similar, but intermediate survival rates when compared with WNT and Group 3 medulloblastomas (Taylor et al., 2012). 2.4 Medulloblastoma treatment Treatment for medulloblastoma has not changed considerably over the past 15 years, and is determined primarily by the risk-group a patient falls into. Patients are considered either average-risk or high-risk, and severity is determined by taking metastatic stage, postoperative residual tumor, patient age and tumor location into consideration (Packer et al., 2003, Pollack and Jakacki, 2011). Briefly, medulloblastomas are considered average-risk instead of high-risk when there is a lack of neuraxis dissemination, minimal residual tumor following surgery, or if a patient is younger than 3 years of age (Merchant et al., 2008). Typically, patients with averagerisk and high-risk medulloblastoma are treated with 2,340 and 3,600 cgy of CSR to the neuraxis respectively and both groups receive a boost to the posterior fossa or tumor site in addition to adjuvant chemotherapy (Pollack, 2011). With recent advances in neuroimaging, neurosurgical technology, radiation therapy and risk-adapted chemotherapy, the 5 year-survival rate for medulloblastoma has reached 70%, a dramatic increase from 50% only 25 years ago (Bleyer, 1999, Gatta et al., 2009). 2.5 Neuropsychological late effects of medulloblastoma treatment All childhood cancer survivors are at risk of experiencing long term consequences from their treatment, but brain tumor survivors are most vulnerable to the negative effects (Winick, 2011). One study reported 91.6% of 1877 CNS tumor survivors were affected by at least one chronic medical condition (Anderson and Kunin-Batson, 2009), and others have demonstrated % of all CNS tumor survivors experience attention and concentration difficulties (Turner et al., 2009, Winick, 2011). The location of posterior fossa tumors alone is enough to impact a

22 11 child s neuropsychological functioning, with several studies having demonstrated neuropsychological declines in patients treated with surgery alone (Levisohn et al., 2000, Ris et al., 2008). However, patients treated with CSR, regardless of tumor location, experience a spectrum of chronic long-term cognitive, neurologic and endocrine impairments that typically worsen over time (Mabbott et al., 2005, Ellenberg et al., 2009, Merchant et al., 2010). Specifically, treatment with CSR has been correlated with a decline in several neuropsychological domains including intellectual functioning, visual-perceptual ability, memory, learning, processing speed, attention and executive functioning (Kieffer-Renaux et al., 2000, Spiegler et al., 2004, Mabbott et al., 2005, Mabbott et al., 2008). To evaluate neuropsychological functioning, neuropsychologists typically administer standardized tests that evaluate how brain functioning affects an individual s abilities and development. An array of measures ranging from broad indices to specific domains such as attention and visual-motor integration are commonly used (Anderson and Kunin-Batson, 2009). The most widely used broad measure of neuropsychological functioning is the overall intelligence quotient (IQ), and it has been used extensively in both clinical populations and healthy children alike. The widespread use of this broad measure has allowed for normal development to be characterized and also for several large-scale multi-institutional studies on neuropsychological outcome in pediatric brain tumor patients to be conducted (Levisohn et al., 2000, Mulhern et al., 2004, Spiegler et al., 2004, Mabbott et al., 2008, Edelstein et al., 2011). In order to arrive at an overall mean intelligence score, processing speed, working memory, verbally expressed knowledge and visual-spatial abilities are examined (Wechsler, 2003). Taken together, these tests estimate intellectual ability, and capture many of the core deficits experienced by medulloblastoma patients such as poor processing speed and working memory (Mabbott et al., 2008, Law et al., 2011). Factors that have been shown to impact neuropsychological functioning most dramatically following CNS tumor treatment include age at diagnosis, tumor location, chemotherapy, the field and dose of radiation administered, and the presence of postsurgical/medical complications (Ris et al., 2001, Mabbott et al., 2008, Turner et al., 2009). Each contributing factor will be discussed below.

23 Age at diagnosis A younger age at diagnosis has been associated with lower IQ and academic achievement scores following CSR (Spiegler et al., 2004, Mabbott et al., 2005, Edelstein et al., 2011). The observed neuropsychological decline following CSR is thought to result from a hindered rate of development rather than through a loss of previously acquired skills (Ris et al., 2001, Palmer et al., 2003, Mabbott et al., 2005). Thus, young children at early stages of brain maturation with underdeveloped academic and intellectual skills are at greatest risk of neuropsychological impairment following CSR. Several studies have avoided using conventional CSR to treat young medulloblastoma patients, a strategy that has shown promise in preserving neuropsychological outcome (Lafay-Cousin et al., 2009) Tumor location Tumors arising in the cerebral hemispheres have been suggested to pose the greatest neuropsychological risk, as they could result in higher-order cognitive difficulties, compared with tumors arising in the posterior fossa that are more likely to be associated with motor deficits (Patel et al., 2011). However, several studies have demonstrated impairments in attention, memory, academic and intellectual functioning in children with posterior fossa tumors treated with CSR (Spiegler et al., 2004, Mabbott et al., 2005, Reeves et al., 2006). Elucidating the discrete cerebellar regions responsible for mediating these neuropsychological deficits is an area of ongoing investigation (O'Halloran et al., 2012). One study demonstrated that children who underwent cerebellar tumor resection but who received neither CSR nor chemotherapy presented with different deficits depending on the precise tumor location. Namely, left cerebellar hemisphere tumors were related to visual-spatial deficits while tumors in the right cerebellar hemisphere were related to language deficits (Levisohn et al., 2000). Transient impairments of speech and communication are common following surgery for posterior fossa tumors (Ersahin et al., 1996, Law et al., 2012). Thus, while the exact impact of tumor location on neuropsychological outcome is still being elucidated, tumor location appears to be important Post-Surgical/Medical Complications The presence and extent of medical complications have been shown to impact neuropsychological functioning. Hydrocephalus, or fluid buildup in the brain, has been correlated with lower IQs and academic skills in pediatric medulloblastoma survivors (Hardy et

24 13 al., 2008). Furthermore, a recent study demonstrated that patients who experienced any of the following post-surgical complications: motor deficits, cranial nerve deficits, mutism and/or meningitis, had greater impairments in information processing speed than patients who did not experience postsurgical complications (Mabbott et al., 2008). While the specific contributions of individual complications to poor neuropsychological outcome remain to be elucidated, the presence of postsurgical complications clearly has a negative effect Chemotherapy Although the neuropsychological late effects of chemotherapy are less dramatic than with cranial radiation, they are not entirely insignificant (Anderson and Kunin-Batson, 2009). Neuropsychological deficits most frequently observed in leukemia patients treated with the chemotherapy agent methotrexate are in the domains of visual processing, visual-motor functioning and attention (Hill et al., 1997, Buizer et al., 2005). Deficits in visual processing negatively affect the way visual information is interpreted and understood, while visual-motor deficits result in impaired skills such as handwriting and the ability to copy drawings. One study demonstrated that patients treated with a combination of methotrexate, cytosine arabinoside and hydrocortisone for leukemia had poorer attention, memory and visual processing than newly diagnosed patients (Brown et al., 1992). It is likely that different chemotherapy agents, coupled with intensity, timing and method of administration all result in different degrees of neurotoxicity. For example, children who received an additional 3 weeks of chemotherapy, regardless of the agent used, performed more poorly on visual-motor integration tasks (Kaleita et al., 1997). In contrast, some studies did not find correlations between chemotherapy administration and intellectual abilities (Copeland et al., 1996, von der Weid et al., 2003). Thus, chemotherapy alone does not appear to be entirely benign, especially with respect to specific neuropsychological domains such as attention and visual processing and visual motor integration; however, the effects are not nearly as pronounced or consistent as they are with CSR Cranio-spinal radiation Neuropsychological declines in children treated with CSR do not present immediately but have been observed within the first 12 months, and can be delayed by 1 to 2 years (Radcliffe et

25 14 al., 1992, Mulhern and Palmer, 2003, Palmer et al., 2010). The delayed nature of this decline suggests CSR induces subtle, non-traumatic form of damage to the developing brain. During CSR, no brain structures are shielded from radiation; however, not all structures are equally susceptible to radiation-induced damage. It is plausible that structures and tracts with long periods of development are especially vulnerable to insult during childhood. Namely, the prefrontal cortex matures later than its caudal counterparts and its myelination continues into the third decade of life (Sowell et al., 1999, Casey et al., 2000, Ullen, 2009, Teffer and Semendeferi, 2012). Interestingly, a study assessing white matter integrity following whole brain CSR demonstrated frontal lobe white matter integrity was preferentially disrupted compared with other brain regions (Qiu et al., 2007). Increases in whole brain white matter volume occur during childhood and these increases continue well into adolescence (Giedd et al., 1999, Paus et al., 1999, Lebel and Beaulieu, 2011). This normal developmental structural change has been proposed to underlie the relative gains in selective attention, working memory and problem-solving that occur with increasing age (Anderson et al., 2001, Wolfe et al., 2012). A longitudinal neuroimaging study that compared healthy controls with medulloblastoma patients treated with CSR and a boost to the PF documented a relative white matter decrease of 1.1% per year, a stark contrast from the 5.4% per year increase observed in healthy controls (Reddick et al., 2005). It is therefore not surprising that children treated with CSR experience deficits in neuropsychological processes associated with white matter such as processing speed and working memory (Mabbott et al., 2008, Law et al., 2011). The particular vulnerability of white matter to CSR induced injury may be due in part to its unique vascular architecture. White matter contains long stretches of vessels with few branches while gray matter contains large numbers of short branched vessels (Reinhold et al., 1990). These structural differences result in blood flow in white matter that is 1/3 of that in gray matter (Tuor et al., 1986). In addition to having a longer developmental period, the frontal lobe has lower cerebral blood flow than the temporal, parietal and occipital cortices (Ito et al., 2003). Thus, its late developmental period coupled with its decreased blood flow renders the frontal lobe more vulnerable to CSR induced injury than other brain regions. Interestingly, decreased

26 15 frontal lobe white matter volume has been shown to correlate with deficits in sustained attention following CSR (Reddick et al., 2003). Brain regions harboring stem and progenitor cells that continue to undergo neurogenesis are known to be particularly sensitive to radiation. In mammals, neurogenesis occurs in the dentate gyrus of the hippocampus and in the subventricular zone of the lateral ventricles (Blomstrand et al., 2012). Rodent studies have demonstrated the importance of neurogenesis in hippocampal dependent memory formation (Shors et al., 2001), and it is hypothesized that damage to the hippocampus is one of the critical determinants of poor neuropsychological outcome following CSR (Blomstrand et al., 2012). Radiation damages endothelial cells, one of the cell types that comprise the blood brain barrier (BBB) (Li et al., 2003). Disruption to the BBB can lead to edema formation, or fluid buildup in the brain, and also allows peripheral leukocytes such as macrophages and neutrophils to infiltrate the brain (Siu et al., 2012). The infiltration of inflammatory cells can result in secondary brain injury through the production of neurotoxic pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-a) and reactive oxygen species (ROS) (Siu et al., 2012). This dynamic processes can result in tissue damage, and may underlie some of the cognitive deficits observed in pediatric brain tumor survivors (Wong and Van der Kogel, 2004). 2.6 Recent advances and moving forward In light of the negative sequalea discussed above, strategies for reducing CSR dose in medulloblastoma patients has been a topic of intensive investigation, particularly for young and average-risk patients. Average-risk patients are considered to have a more favorable outcome than high-risk patients, thus therapy de-escalation was first attempted in the mid-1990 s for this group (Packer et al., 1999). Reducing the dose from 3600 cgy to ~2300 in average-risk patients was successfully accomplished with the addition of combination chemotherapy, and overall survival rates were comparable to those receiving 3600 cgy (Packer et al., 1999, Taylor et al., 2003, Merchant et al., 2008). To date, average-risk patients continue to be treated with ~2300 cgy. However, despite preserving overall survival rates, reducing the CSR dose has failed to prevent the neuropsychological decline (Ris et al., 2001). Following whole brain CSR, medulloblastoma patients have historically received a boost of radiation to the entire PF, bringing the total PF radiation dose to a maximum of 5,000-6,000

27 16 cgy (Pollack and Jakacki, 2011). However, recent years have seen the emergence of technological advances aimed at reducing complications associated with CSR. Namely, advances in radiation oncology have led to the development of conformal techniques, allowing for threedimensional reconstructions of patient brains to guide treatment planning (Wolden et al., 2003). Thus, focal conformal boosts to the tumor bed are sometimes used in place of a boost to the entire PF, most commonly in average-risk patients. A boost to the entire PF delivers considerable radiation to several critical brain structures located outside the targeted area, including the cochlea, temporal lobes, parotid glands, pituitary and hypothalamus, while focal conformal therapy to the tumor bed delivers considerably less radiation to these structures (Wolden et al., 2003). A recent study demonstrated that treatment with focal conformal therapy to the tumor bed resulted in disease control comparable to treatment to the PF in average-risk medulloblastoma patients (Merchant et al., 2008). It seems plausible that focal conformal therapy would result in fewer neuropsychological and neuroendocrine complications than a boost to the entire posterior fossa, but this correlation has yet to be clearly established. Recent strategies for delaying or avoiding radiotherapy in children younger than 5 that have yielded positive results include using intraventricular chemotherapy or intensified systemic chemotherapy and high-dose marrow-ablative chemotherapy (Rutkowski et al., 2010). Additionally, a recent international meta-analysis on survival and prognostic factors of early childhood medulloblastoma concluded that desmoplastic/nodular variants is a favorable prognostic factor independent of metastatic disease in young children, and the authors suggest de-escalation of CSR might be warranted in this population (Rutkowski et al., 2010). In light of the recent subgrouping of medulloblastoma into four distinct subgroups, it is becoming clear that treating medulloblastoma as a single disease may no longer make biological sense. It has been proposed that patients with WNT medulloblastomas might benefit from therapy de-escalation, as it is possible they are being over treated with current treatment protocols (Taylor et al., 2012). Alternatively, it is plausible that patients with Group 3 medulloblsatomas could benefit from novel therapeutic techniques, as they consistently have poorer outcomes than other subgroups despite receiving identical treatment. In order for treatment protocols to become subgroup specific, a thorough understanding of neuropsychological outcome in medulloblastoma patients as a whole and between subgroups is necessary.

28 17 To this end, this thesis will aim to a) examine neuropsychological outcome in medulloblastoma patients as a whole, b) evaluate if there are differences in intellectual outcome between subgroups, and c) assess if treatment intensity has an impact on intellectual functioning in Group 4 patients. 3 Patients and Methods 3.1 Patient information Ninety-one children (28 females and 63 males) were included in this study, and all were treated for medulloblastoma between 1995 and 2012 at the Hospital for Sick Children (Toronto, Canada). The mean age at diagnosis for the entire medulloblastoma sample was 7.53 years (standard deviation 3.39; range ). Our medulloblastoma sample is comprised of 12 patients (13%) with WNT medulloblastomas, 20 patients (22%) with SHH medulloblastomas, 18 patients (20%) with Group 3 medulloblastomas, and 41 patients (45%) with group 4 medulloblastomas. Patient information for each subgroup is detailed in Figure 1. Figure 1 Patient Characteristics. A-D. Detailing the number of patients, the number of males and females, and the age at diagnosis for patients in our entire medulloblsatoma sample, and for each subgroup separately. (B-D are provided for visualization purposes).

29 Materials and Procedures All neuropsychological assessments were conducted following treatment with CSR. Each child underwent at least one clinical neuropsychological assessment and most underwent several, although the number of assessments was not the same for all children. The number of patients assessed with each measure varied across assessment points, since the original data were collected for a variety of different clinical and research assessments, each with their own test batteries. Our patient sample includes some individuals first diagnosed 17 years ago and several tests and versions have changed within that time. Thus, there is considerable variability in both the number of times, and over how many years, patients in our sample were seen. Namely, 1 patient was seen 8 times over the course of 14 years, whereas 29 patients were only seen once. Following retrospective review, scores obtained longitudinally for neuropsychological tests were obtained Intelligence This study included several different test versions used to assess intelligence. Not all versions have the same estimated and indexed scores, therefore, scaled scores obtained from the various test types and versions were considered equivalent in the manner detailed in Table 3. Specifically, measures to assess Full Scale IQ (FSIQ), verbal comprehension (VC), perceptional reasoning (PR), working memory (WM) and processing speed (PS) were obtained by combining scaled scores from the following test versions, where applicable: Wechsler Intelligence Scale for Children Third & Fourth Editions (WISC-III, WISC-IV), Wechsler Preschool and Primary Scale of Intelligence Revised and Second Edition (WPPSI-R, WPPSI-III), Wechsler Abbreviated Scale of Intelligence (WASI) and Wechsler Adult Intelligence Scale Third & Fourth Editions (WAIS-III, WAIS-IV). In order to make comparison across test versions, each child s raw scores were converted to age-corrected scaled scores by using normative data for the neuropsychological test provided in the manual for that particular test. The Wechsler technical manual indicates that equivalency studies were conducted between all test versions and between all families of Wechsler tests, and provides correlational data and details of test reliability (Wechsler, 2003). Namely, the WISC-IV FSIQ correlates with the WISC-III, WPPSI-III and WAIS-III FSIQ s (r=.89), and with the WASI FSIQ (r=.86) (Wechsler, 2003). Furthermore, the WPPSI-III FSIQ s correlates with the WPPSI-R FSIQ (r=.86) and with the WISC-III FSIQ

30 19 (r=.89), and the WAIS-III FSIQ correlates with WISC-III FSIQ (r=.88) (Campbell et al., 2008). This suggests scores obtained from all Wechsler tests and versions can be compared as long as scaled scores are used. WISC-III WISC-IV WPPSI-R WPPSI-II WASI WAIS-III WAIS-IV FSIQ FSIQ FSIQ FSIQ FSIQ FSIQ FSIQ FSIQ VC VC VC VIQ VIQ VIQ VC VC PR PO PR PIQ PIQ PIQ PO PO WM FD WM WM WM PS PS PS PS PS Table 3 Indexed scores considered equivalent across different test types and versions. FD: Freedom from Distractibility; FSIQ: Full Scale Intelligence Quotient; PIQ: Performance Intelligence Quotient; PO: Perceptual Organization; PR: Perceptual Reasoning; PS: Processing Speed; VC: Verbal Comprehension; VIQ: Verbal Intelligence Quotient; WM: Working Memory. WISC-III/IV: Wechsler Intelligence Scale for Children Third & Fourth Editions; WPPSI-R/II: Wechsler Preschool and Primary Scale of Intelligence Revised and Second Edition; WASI: Wechsler Abbreviated Scale of Intelligence; WAIS-III/IV: Wechsler Adult Intelligence Scale Third & Fourth Editions. Assessing changes in intelligence is only one method to demonstrate and measure neuropsychological impairment. In order to provide a more complete assessment of neuropsychological impairment, scores obtained from standardized neuropsychological tests designed to assess academic performance, receptive vocabulary, visual motor integration, fine motor skills, memory and attention were also examined Academic Performance To examine academic performance, Math, Reading and Spelling composites were created by combining constructs from the Wide Range Achievement Test (WRAT) and Wechsler Individual Achievement Test (WIAT) because of high correlation between them. Namely, the WIAT-II and WRAT-3 constructs correlated with one another in the following manner: Reading, r=.73; Math, r=.77; Spelling, r=.78 (Campbell et al., 2008). Furthermore, the WIAT-II and WRAT-4 constructs correlated as follows: Reading, r =.78; Math, r=.92; Spelling, r=.64. (Wilkinson, 2006). Additionally, the correlations between the constructs in WIAT-II and WIAT- III are as follows: Reading, r=.85; Math, r=.81; Spelling, r=.86 (Breaux, 2009).

31 Receptive Vocabulary To examine receptive vocabulary, the Peabody Picture Vocabulary Test (PPVT) was used. This test serves as a test of a child s single-word receptive vocabulary in English and is a screening of verbal ability Visual Motor Integration The Beery Visual Motor Integration (VMI) test was used to determine how extensively visual and motor abilities could be integrated. In this test, children were asked to copy geometric forms that increased in difficulty as the test progressed Fine Motor Skills To examine fine motor skills, the mean number of finger taps from both the dominant and non-dominant hand were assessed by averaging over five trials, lasting 10 seconds each Memory To evaluate memory, the Children s Memory Scale (CMS) was used. The CMS is a comprehensive assessment tool that assess auditory and verbal learning and memory, visual and nonverbal learning and memory, as well as attention and concentration (Cohen, 1997) Attention The Connors Continuous Performance Test II was used to assess sustained attention. In this test, children are told to press the space bar when they see any letter except X and not to press the space bar when the see the letter X. By evaluating the child s omissions and commissions, this computerized test measures impulsivity and selective attention (Conners, 2000). 3.3 Assessments Assessments were administered at different time points following diagnosis for each patient. A summary of the number of assessments, tests, versions and the number of observations within each, broken down by medulloblastoma subgroup, can be found in Table 4.

32 Assessment Number Assessment Number Assessment Number Assessment Number Assessment Number Observations - total Observations - WNT Observations - SHH Observations - Group 3 Observations - Group 4 Measure WISC Third Edition Fourth Edition WPPSI Revised Second Edition WASI WAIS Third Edition Fourth Edition WRAT Third Edition Fourth Edition WIAT Second Edition Third Edition PPVT Revised Third Edition Fourth Edition VMI F-TAP CPT Second Edition CMS Table 4

33 22 Table 4 - Number of observations for the different test types in each assessment year. WISC: Wechsler Intelligence Scale for Children; WPPSI: Wechsler Preschool and Primary Scale of Intelligence; WASI: Wechsler Abbreviated Scale of Intelligence; WAIS: Wechsler Adult Intelligence Scale; WRAT: Wide Range Achievement Test; WIAT: Wechsler Individual Achievement Test; PPVT: Peabody Picture Vocabulary Test; VMI: Visual Motor Integration; F- TAP: Finger Tapping; CPT: Conners Continuous Performance Test; CMS: Children s Memory Scale. The median time from diagnosis to the first assessment was 0.4 years (range ), and for those who were seen more than once, the median time from diagnosis to the last assessment was 4.76 years (range ). This information, broken down by medulloblastoma subgroup, is listed in Table 5 Table 5 Neuropsychological assessments. Table listing the time from diagnosis to the first neuropsychological assessment, time from diagnosis to the final neuropsychological assessment, and the average number of assessments for the entire medulloblastoma sample and for each subgroup. 3.4 Medical Variables Gross total resection, where > 95% of the tumor was removed, was achieved in 74 patients (81%). 64 patients (71%) were classified as high risk, and the remainder (27 patients; 30%) were classified as average risk. 89 patients (98%) were treated with CSR; 41 patients (45%) were treated with standard-dose (i.e 3060 to 3940 Gy), and 48 patients (53%) were treated with reduced dose (i.e to 2340 cgy) radiation to the whole brain. All patients treated with CSR received an additional boost, raising the total radiation dose to a range of 4680 to 9540 cgy.

34 23 The type of boost a patient received differed based on the date radiotherapy was administered. Prior to 2006 at the Hospital for Sick Children, average risk patients received a lateral beam boost to the PF, and from 2006 onwards they received a focal conformal boost to the tumor bed. In order to accurately elucidate the effects of cranial radiation on neuropsychological functioning, our patient sample was divided into four categories for analysis, as follows: 1) Patients treated with standard dose CSR and a boost to the PF (n=32; 35%), 2) Patients treated with standard dose CSR and a focal conformal boost to the tumor bed (n=9; 11%), 3) Patients treated with reduced dose CSR and a boost to the PF (n=25; 27%), and 4) Patients treated with reduced dose CSR and a focal conformal boost to the tumor bed (n=23; 25%). Histological classification of the tumors in our medulloblastoma sample revealed the majority of tumors to be of the classic subtype (n=65; 71%), followed distantly by the large cell/anaplastic (n=16; 18%), and desmoplastic (n=10; 11%) subtypes. 43 patients (47%) presented with, and/or had treatment for hydrocephalus in the form of a shunt, external ventricular drain, or a ventriculostomy. 11 patients (12%) in our sample died as a result of tumor recurrence after being seen for at least 1 assessment. As previously discussed, medulloblastoma subgroups differ in their biological and clinical features; thus, it is plausible that certain medical characteristics may present to differing degrees in each subgroup. Medical variables for each subgroup are summarized in Figure 2. Detailed medical information for each patient can be found in Appendix 1 and patients (93%) received adjuvant chemotherapy. The chemotherapy protocols utilized between 1995 and 2012 changed several times. Thus, patients diagnosed at different times were treated with different agents, or with different doses and timing. Namely, 8 different chemotherapy protocols are captured in our patient sample. The protocol names and the therapeutic agents used in each are listed in Table 6. Although certain protocols appear identical based on the chemotherapeutic agents used, they can differ considerably with respect to the timing of administration and doses administered.

35 24 Protocol COG ACNS 0331 Baby POG * ICE MOPP SJMB03 POG 9631 CCG 9961 COG * Agents Used (in order of administration) Vincristine, Cisplatin, Lomustine (CCNU), Cyclophosphamide Cyclophosphamide, Vincristine, Cisplatin, Etoposide Ifosfamide, Carboplatin, Etoposide Mechloroethamine, Vincristine, Procarbazine, Prednisone Vincristine, Cisplatin, Cyclophosphamide (amended to include Amifostine) Cisplatin, Etoposide, Cyclophosphamide, Vincristine Vincristine, Lomustine (CCNU), Cisplatin Cisplatin, Vincristine, Cyclophosphamide, Etoposide Table 6 Therapeutic agents used in chemotherapy protocols. COG: Children s Oncology Group; POG: Pediatric Oncology Group; SJMB: St Jude Medulloblastoma Protocol; CCG: Children s Cancer Group; ICE & MOPP are abbreviations used based on the chemotherapeutic agents administered. * Protocols typically used in children younger than 5 years of age. 3.5 Subgrouping Medulloblastoma Medulloblastoma samples from patients whose neuropsychological data were available to us were assigned subgroups by RNA nanostring the nanostring ncounter Analysis System at the University Health Network Microarray Centre (Toronto, Canada) (Courtesy of Dr. Michael Taylor s laboratory). Nanostring is a non-enzymatic multiplexed assay that digitally measures mrna in a sample by using sequence specific probes (Geiss et al., 2008, Kulkarni, 2011). This technology identifies and counts individual mrna transcripts, a phenomenon that allows gene transcription to be captured accurately. This technique is in contrast to technologies like polymerase chain reaction (PCR) that rely on enzymatic amplification of RNA for signal detection (Geiss et al., 2008). Thus, nanostring allows hundreds of unique transcripts to be detected and counted in a single reaction. Northcott and colleagues designed a custom CodeSet containing probes against 22 medulloblastoma subgroup-specific genes (Northcott et al., 2012b). This assay was tested rigorously; nanostring results were compared with several samples of known subgroup, and this CodeSet was found to be powerful enough to reliably subgroup medulloblastoma samples (Northcott et al., 2012b). This codeset is described in Table 7.

36 Figure 2 25

37 26 Figure 2 Medical Variables. Left panels show the proportions of each medical variable for the entire medulloblastoma sample (n=91). Right panels show the proportions of the same medical variables for each medulloblastoma subgroup. A. The extent of tumor resection. B. Clinical Risk. C. The dose of radiation (standard vs. reduced) and the type of boost (posterior fossa vs. tumor bed) administered. D. The histological classification of tumors. LCA: Large Cell and Anaplastic. E. The presence or absence of hydrocephalus. Subgroup WNT SHH Group 3 Group 4 Housekeeping genes Genes in codeset WIF1, TNC, GAD1, DKK2, EMX2 PDLIM3, EYA1, HHIP, ATOH1, SFRP1 KCNA1, EOMES, KHDRBS2, RBM24, UNC5D, OAS1 KCNA1, EOMES, KHDRBS2, RBM24, UNC5D, OAS1 ACTB, GAPDH, LDHA Table 7 Nanostring CodeSet. Table listing the 22 probes against medulloblastoma subgroupspecific genes that were used to classify medulloblastoma tissue into subgroups by Nanostring technology. For technical details on medulloblastoma subgrouping by nanostring, please refer to the methods section in Northcott et al. s 2012 manuscript entitled Rapid, reliable, and reproducible molecular sub-grouping of clinical medulloblastoma samples. 3.6 Statistical Analysis To examine neuropsychological and intellectual outcome in medulloblastoma patients following treatment, longitudinal analyses were conducted with growth curve analysis. Growth curve analysis is a mixed model regression technique specifically designed to examine how the shape of each individuals data changes over time (Singer, 2003). This analysis can handle unbalanced and missing data, a common phenomenon in clinical samples and is thus able to account for the different times after diagnosis that assessments were conducted in our patient sample (Palmer and Royall, 2010). The mixed model assumes there is an underlying systematic change in the data (Willett, 1994, Holditch-Davis et al., 1998), thus the linear model was generated for all neuropsychological measures, and the curvilinear model (i.e. quadratic) model was generated for all measures containing at least three data points. The model that provided the best fit for the data was selected. When both linear and curvilinear models were generated, the curvilinear model was reported when both were found to be significant. A significant quadratic

38 27 term indicates the slope of the domain being assessed curves over time because the rate of change differs as time increases. Because the models generated are based on data from a combination of children assessed several times, and some only assessed once, individual patient trajectories are included to provide the reader with a visualization of the individual patient data that resulted in the modeled change. Moreover, group means, where all points over time were considered, were examined to establish overall group differences. This mixed model technique was applied using the PROC MIXED procedure in the SAS software, version 9.1 (SAS institute). Results were considered significant if P < Aim 1 To assess neuropsychological outcome following treatment in our entire medulloblastoma sample, growth curve analysis was conducted to evaluate the change or stability of scores for the following neuropsychological domains: intelligence, academic performance, receptive vocabulary, visual motor integration, fine motor skills, memory and attention. Following this neuropsychological characterization of our medulloblastoma sample, the impact of demographic, medical and treatment factors were evaluated. The effect of these factors on intellectual functioning was examined first, and when found to result in significantly different intellectual outcomes, subsequent analyses were conducted to examine their impact on additional measures of neuropsychological functioning. This approach was taken to further characterize any differences in neuropsychological functioning observed between the groups. Specifically, our entire medulloblastoma sample was stratified by the following factors individually: age at diagnosis (i.e. < 7.26 years vs. > 7.26 years), clinical risk (i.e. average vs. high), hydrocephalus (i.e. presence vs. absence), CSR dose and field (i.e. (1) standard vs. reduced dose, (2) standard vs. reduced dose in only those patients who received a lateral beam boost to the PF, and (3) standard vs. reduced dose in only those patients who received a focal conformal boost to the TB), extent of tumor resection (i.e. gross total vs. subtotal), and intellectual outcome for each condition within the factor was compared. A boost to the PF delivers considerable radiation to several critical brain structures located outside the targeted area, while focal conformal therapy to the TB delivers substantially less radiation to these structures (Wolden et al., 2003). Thus, radiation field (i.e. type of boost received) should be accounted for to accurately elucidate the effects of radiation on intellectual functioning. Prior to 2006 at the Hospital for Sick Children, average risk patients received a lateral beam boost to the

39 28 PF, and from 2006 onwards they received a focal conformal boost to the TB, regardless of the CSR dose received. In order to create and compare the growth curves of patients with each condition, the factor being assessed was specified in the CLASS statement in the SAS script Aim 2 Growth curve analysis was conducted to evaluate if intellectual functioning following CSR differed as a function of medulloblastoma subgroup. To generate growth curves for multiple subgroups in one model, subgroup was specified as the CLASS statement, and comparisons between the growth curves were made using the estimate and contrast statements in the SAS script. Chi-square analyses were conducted to examine if the proportion of factors shown to predispose to poor intellectual outcome in Aim 1 differed between subgroups Aim 3 To elucidate the intellectual cost associated with CSR dose and field in Group 4 patients, growth curve analysis was conducted in an analogous manner to that in Aim 1b. Namely, intellectual functioning in Group 4 patients was examined as a function of CSR dose and field by stratifying Group 4 patients by 1) standard vs. reduced dose, 2) standard vs. reduced dose in only those patients who received a lateral beam boost to the PF, and 3) standard vs. reduced dose in only those patients who received a focal conformal boost to the TB.

40 29 4 Results 4.1 Aim Aim 1a: Neuropsychological outcome in all medulloblastoma patients Significant declines were observed in 20 out of the 24 measures of neuropsychological functioning over the modeled time period in our entire medulloblastoma sample (F s > 5.1 (range ), p s < 0.05). The only non-significant declines were in fine motor skills (as measured by the finger tapping tests) and attention (measured with the CPT-II). Intercepts represent the modeled baseline functioning (median time from diagnosis to first assessment was 0.4 years), and slopes represent the change in functioning over time (median time from diagnosis to final assessment was 4.76 years and the maximum time was years). Most declines in neuropsychological measures fit the linear model, with the exception of PRI, the reading composite of academic performance, and attention/concentration (measured with the CMS), which had significant quadratic terms, indicating an attenuation of the decline. These findings are in agreement, and replicate, what has previously been shown in the literature (Kieffer- Renaux et al., 2000, Ris et al., 2001, Palmer et al., 2003, Spiegler et al., 2004, Mabbott et al., 2005, Mabbott et al., 2008). Intercepts and slopes for the neuropsychological measures examined in our entire medulloblastoma sample are provided in Table Aim 1b: Intellectual outcome as a function of demographic, medical and treatment variables Age at diagnosis When our medulloblastoma sample was stratified by age at diagnosis (i.e. by the median split of 7.26 years), PSI was the only measure of intellectual functioning to differ significantly between groups (F=5.27; p=0.008). Children younger than 7.26 years at time of diagnosis performed more favorably than older children, a counterintuitive finding given that a younger age has been associated with lower intelligence scores following CSR (Spiegler et al., 2004, Maddrey et al., 2005, Edelstein et al., 2011). However, group means for all other measures of intellectual functioning (i.e. FSIQ, PRI, VCI and WMI) were in the expected direction, with younger children performing more poorly than older children following treatment, despite not reaching significance. There were no significant differences in mean slope between the groups.

41 30 Group means, overall group differences, intercepts and slopes for measures of intellectual functioning can be found in Supplementary Tables 1 & Extent of tumor resection None of the modeled trajectories for measures of intellectual functioning in our medulloblastoma sample differed as a function of extent of tumor resection. Group means, overall group differences, intercepts and slopes for measures of intellectual functioning can be found in Supplementary Tables 3 & Hydrocephalus Stratifying medulloblastoma patients by the presence or absence of hydrocephalus revealed that patients with hydrocephalus performed more poorly than patients without hydrocephalus. The groups were found to differ significantly on all measures of intellectual functioning, and were subsequently examined for differences in additional measures of neuropsychological functioning, analyses that revealed significant differences in the reading and spelling composites, receptive vocabulary, visual motor integration, and the attention/concentration index of the CMS (F s > 4.11, p s < 0.05). All other memory domains examined with the CMS were not significantly different between groups. Patients with hydrocephalus presented with lower baseline scores for all measures of intellectual functioning. Namely, patients with hydrocephalus presented with FSIQ, PSI and VCI scores that were approximately 1 SD below the normative mean, a phenomenon not observed in patients without hydrocephalus. Mean slopes for the groups were significantly different for FSIQ, PRI, the reading composite, and VMI (F s > 2.14, p s < 0.05). Patients with hydrocephalus experienced more dramatic declines than patients without hydrocephalus, as indicated by larger negative slopes in nearly all measures of neuropsychological functioning (Figure 3: FSIQ is shown as an example, but similar declines were seen for nearly all other measures of neuropsychological functioning). Group means, overall group, and mean slope differences for measures of neuropsychological functioning showing significant differences are provided in Table 9, and intercepts and slopes are provided Table 10. Group means, overall group differences, intercepts and slopes for memory measures can be found in Supplementary Tables 5 & 6. Thus, having hydrocephalus appears to

42 31 dramatically impact neuropsychological functioning, both at baseline and over time in medulloblastoma patients. Estimated Intercepts and Slopes for Neuropsychological Measures Domain Intercept Slope Quadratic Estimate SE Estimate SE Estimate SE Intellectual functioning Full Scale IQ * Perceptual Reasoning Index * * 0.09 Processing Speed Index * Verbal Comprehension Index * Working Memory Index * Academic performance Math * Reading * * 0.09 Spelling * Receptive vocabulary PPVT * Visual motor integration Beery - VMI * Memory CMS - Visual Immediate * CMS - Visual Delayed * CMS - Verbal Immediate * CMS - Verbal Delayed * CMS - General Memory * CMS - Attention/Concentration * * 0.29 CMS - Learning * CMS - Delayed Recognition * Fine motor skills Dominant hand Non-dominant hand * * 0.01 Attention CPT-II-Omissions CPT-II-Commissions * CPT-II-Hit Reaction Time CPT-II-Hit Reaction Time - SE Table 8 - Estimated intercepts and slopes for neuropsychological measures in all medulloblastoma patients (n=91). The following scores are standard scores (i.e. mean, 100, standard deviation, 15): Intellectual functioning, Academic Performance, Receptive Vocabulary, Visual Motor Integration and Memory. Fine motor skills are z scores, and Attention are T scores (i.e. mean, 50, standard deviation 10). Higher T scores indicate poor performance. * p < 0.05

43 32 A B Figure 3 A. Observed declines in FSIQ scores over time for patients with and without hydrocephalus (n=43/n=48). B. Estimated declines in FSIQ in patients with and without hydrocephalus in a model that includes linear and quadratic terms. Overall group difference, * p < Table 9 Group means; p values for overall group and mean slope differences for neuropsychological measures when medulloblastoma patients were stratified by the presence/absence of hydrocephalus. Presence of hydrocephalus (n=43); absence of hydrocephalus (n=48).

44 33 Table 10 - Estimated intercepts and slopes for measures of neuropsychological functioning in medulloblastoma patients stratified by the presence/absence of hydrocephalus. All models presented are significant (i.e. p < 0.05) * p < Clinical Risk None of the modeled trajectories for measures of intelligence differed as a function of clinical risk in our medulloblastoma sample. Group means, overall group differences, intercepts and slopes for measures of intellectual functioning can be found in Supplementary Tables 7 & Radiation Dose To elucidate the effect of standard vs. reduced dose CSR on intellectual functioning, our

45 34 medulloblastoma sample was stratified by the following: 1) CSR dose alone, 2) CSR dose in only those patients who received a PF boost, 3) CSR dose in only those patients who received a TB boost Standard vs. Reduced dose None of the modeled trajectories for measures of intelligence differed as a function of radiation dose. Group means, overall group differences, intercepts and slopes for measures of intellectual functioning can be found in Supplementary Tables 9 & Standard dose PF boost vs. Reduced dose PF boost None of the modeled trajectories for measures of intelligence differed as a function of radiation dose when only those patients who received a lateral beam boost to the PF were included in the analysis. Group means, overall group differences, intercepts and slopes for measures of intellectual functioning can be found in Supplementary Tables 11 & Standard dose TB boost vs. Reduced dose TB boost A boost to the TB does not deliver widespread radiation to multiple brain structures, thus examining standard vs. reduced dose in this group should have provided the most accurate information regarding the impact of CSR dose on intellectual functioning. None of the modeled trajectories for measures of intelligence differed as a function of radiation dose when only those patients who received a boost to the TB were included in the analysis; however, some qualitative observations can be made. Most notably, patients who received reduced dose CSR displayed stable functioning over time, and sometimes displayed increases, in measures of PRI and WMI (Shown in Figure 4 blue lines). No qualitative observations can be made about patients who received standard dose because longitudinal data were only available for two patients. The lack of significance in the growth curve models likely resulted from the unequal and small sample sizes (n=9/n=23), and from the shortage of longitudinal data in this comparison group. Group differences, intercepts and slopes for measures of intellectual functioning are provided in Supplementary tables 13 & 14.

46 35 Standard Reduced Standard Reduced Figure 4 Observed declines in PRI and WMI scores in patients who received a boost to the TB, treated with either standard (n=9) or reduced dose (n=23) CSR. Results from Aim 1 indicate that hydrocephalus clearly predisposes to poor neuropsychological outcome in medulloblastoma patients, both at baseline, and over time. Results from Aim 1 also suggest, albeit qualitatively, that treatment with reduced dose CSR and a TB boost might mitigate declines in certain measures of intellectual functioning. 4.2 Aim 2: Intellectual Outcome as a Function of Medulloblastoma Subgroup Plotting FSIQ scores for patients within each subgroup visibly demonstrated that all subgroups declined following treatment with CSR. The observed FSIQ scores over time for patients within each subgroup are shown in Figure 5. This figure demonstrates that Group 4, Group 3 and SHH, but not WNT, have considerable longitudinal data. Overall group means for measures of intellectual functioning in each subgroup are provided in Table 11. These means suggest WNT did not differ considerably from the other subgroups, but had greater variability across all measures examined. In light of the scarce longitudinal data in the WNT group, highly variable scores and similar trajectory to other subgroups, the WNT subgroup was removed from all subsequent analyses. This was done to prevent the generation of unstable longitudinal models.

47 36 Figure 5 Observed decline in FSIQ over time for all patients within each subgroup. Stratifying medulloblastoma patients by subgroup (i.e. by Group 4, Group 3 and SHH) revealed subgroups differ in their intellectual functioning following treatment. Significant overall group differences between subgroups were observed in PRI, PSI and WMI. Specifically, when all scores across time were considered, SHH patients performed more favorably than Group 4 patients in PRI (F=3.89; p=0.0259); Group 3 patients performed more favorably than both SHH and Group 4 patients in PSI (F s > 3.7; p s < 0.05); and Group 3 patients performed more favorably than SHH patients in WMI (F=4.06; p=0.0235). Overall group means for measures of intellectual functioning in each subgroup can be found in Table 11, and the significant overall group differences are highlighted. To arrive at an overall group difference, both the mean values over time and slopes are considered. A summary of overall group differences between subgroups for all measures of intellectual functioning can be found in Supplementary Table 15.

48 37 Table 11 Group means and standard error for measures of intelligence in each subgroup. * Significant overall group difference between SHH and Group 4; ** Significant overall group difference between SHH and Group 3; *** Significant overall group difference between Group 3 and Group 4. p < 0.05 for all significant comparisons. Because WNT was removed from the longitudinal analyses, no overall group comparisons were made with WNT. The subgroups did not differ significantly in how their scores changed over time (i.e. in mean slope) (See supplemental Table 15). However, qualitatively, it appears that despite performing more favorably than Group 4 and SHH patients on several measures of intellectual functioning at baseline, Group 3 patients decline more dramatically than SHH on all measures of intellectual functioning, and more dramatically than Group 4 patients on some measures over time. This can be gleaned from Table 12, where intercepts and slopes for all measures of intellectual functioning in Group 4, Group 3 and SHH are provided. Moreover, it appears that while SHH patients presented with similar, and sometimes lower, baseline scores than Group 3 and Group 4, SHH patients experienced less dramatic declines over time. Observed and modeled

49 38 declines in PRI scores for Group 4 and SHH are shown in Figure 6, observed and modeled declines in PSI scores for Group 4, Group 3 and SHH are shown in Figure 7, and observed and modeled declines in WMI scores for Group 3 and SHH are shown in Figure 8. Table 12 - Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by medulloblastoma subgroup. All models presented are significant (i.e. p < 0.05) * p < A B Figure 6 A. Observed declines in PRI scores over time for patients in Group 4 (n=41) and SHH (n=20). B. Estimated declines in PRI scores in a model that has linear and quadratic terms.

50 39 A B Figure 7 A. Observed declines in PSI scores over time for patients in Group 4 (n=41), Group 3 (n=18), SHH (n=20). B. Estimated declines in PSI scores in a model that has linear terms. A B Figure 8 A. Observed declines in WMI scores over time for patients in Group 3 (n=18) and SHH (n=20). B. Estimated declines in WMI scores in a model that has linear and quadratic terms. Results from Aim 1b-i suggested an older age at diagnosis might predispose to poor PSI, a phenomenon that could explain the differences in PSI observed between some subgroups. However, patient age was not statistically different between subgroups included in the growth curve analysis (i.e. Group 4, Group 3 and SHH): χ² (2, N=78) = , p = , and therefore cannot account for this finding. Results from Aim 1b-iii demonstrated hydrocephalus predisposes to poor neuropsychological outcome in medulloblastoma patients following treatment. The incidence of hydrocephalus was not significantly different between subgroups included in the growth curve

51 40 analysis (i.e. Group 4, Group 3 and SHH): χ² (2, N=78) = , p = Thus, hydrocephalus cannot explain the differences observed in certain measures of intellectual functioning between subgroups. Results from Aim 2 indicate patients in Group 4 have the poorest intellectual outcome and patients in Group 3 have the most favorable outcome following treatment. Qualitatively, it appears SHH patients have the most stable intellectual functioning over time following treatment. Taken together, these results demonstrate medulloblastoma subgroups have heterogeneous intellectual outcomes following treatment. 4.3 Aim 3: Intellectual outcome as a function of treatment intensity in Group 4 patients No differences in intellectual functioning were observed when Group 4 patients were stratified by the following: 1) CSR dose alone, 2) CSR dose in only those Group 4 patients who received a PF boost, 3) CSR dose in only those Group 4 patients who received a TB boost. Group means and overall group differences for measures of intellectual functioning in Group 4 patients stratified by all three above mentioned conditions can be found in Supplementary Tables 16, 18 & 20, and intercepts and slopes for measures of intellectual functioning can be found in Supplementary Tables 17, 19 & 21. Despite the generation of non-significant longitudinal models, qualitatively, group means suggest Group 4 patients treated with reduced dose CSR and a TB boost (n=7) performed more favorably than patients treated with standard dose CSR and a TB boost (n=6), on all measures of intellectual functioning, except processing speed. FSIQ: vs , PRI: vs , VCI: vs , WMI: vs Notably, patients treated with reduced dose CSR were 1 standard deviation (1 SD = 15) below patients treated with standard dose CSR in PRI. The lack of significant difference between these group means is likely due to the small sample sizes. Results from Aim 3 suggest that treatment with reduced dose CSR and a TB boost may mitigate some of the intellectual declines observed following treatment in Group 4 patients.

52 41 5 Discussion In this thesis, neuropsychological and intellectual functioning were examined in medulloblastoma patients following treatment. Our medulloblastoma sample was stratified by several demographic, medical and treatment factors to evaluate their impact on functioning. Differences were examined by comparing overall means (i.e. including all time points in a group) and by examining changes over time (i.e. up to 14 years post-diagnosis) both within and between groups. The novel findings from this thesis are as follows: 1. Among the demographic, treatment and medical factors examined, hydrocephalus most clearly predisposes to poor neuropsychological functioning in medulloblastoma patients. 2. Medulloblastoma subgroups have heterogeneous intellectual outcomes following treatment. All subgroups experience intellectual declines following treatment. When comparing the subgroups, Group 4 performs most poorly, and Group 3 has the best overall outcome following treatment. 5.1 Hydrocephalus Results from Aim 1 demonstrate that the presence of hydrocephalus clearly predisposes to greater declines in neuropsychological functioning following treatment with CSR. Hydrocephalus is defined as the excessive accumulation of cerebrospinal fluid (CSF) in the CNS ventricular system and results in increased intracranial pressure (ICP) (Erickson et al., 2001). Hydrocephalus has been correlated with lower intellectual functioning and academic skills in pediatric medulloblastoma survivors (Hardy et al., 2008) and ependymoma survivors alike (Merchant et al., 2004); however, no equivalent longitudinal study has been conducted to my knowledge. As such, this thesis makes an important contribution to the pediatric medulloblastoma field regarding predictors of neuropsychological outcomes. It is well documented that children with hydrocephalus, regardless of the underlying cause, perform more poorly on measures of intellectual functioning than healthy developing children, and also as compared to children with the same underlying etiology who do not develop hydrocephalus (Erickson et al., 2001). For example, only 54% of patients with spina bifida who developed hydrocephalus had intelligence scores within the normal range, while 76% of patients

53 42 with spina bifida who didn t develop hydrocephalus had intelligence scores in the normal range (Mirzai et al., 1998). In our medulloblastoma sample, patients with hydrocephalus had significantly lower baseline scores (i.e. shortly after treatment) on several measures of neuropsychological functioning than patients without hydrocephalus. One study demonstrated that pediatric brain tumor patients with hydrocephalus performed more poorly than patients without hydrocephalus on measures of intelligence, executive functioning, visual-motor, and fine-motor functioning, prior to treatment (Brookshire et al., 1990). Brookshire s findings raise the possibility that patients in our sample who presented with hydrocephalus at diagnosis would have performed more poorly than patients without hydrocephalus, but this information cannot be gleaned from the present study. In light of the considerable emphasis placed on delineating the neuropsychological late effects of treatment for medulloblastoma, it will be important to tease out the contribution of presenting with hydrocephalus. This is especially important if patients neuropsychological baseline functioning are routinely examined following treatment, as was the case in the present study. The present study demonstrates that in addition to presenting with lower baseline neuropsychological scores, patients with hydrocephalus continue to decline more dramatically on measures of neuropsychological functioning following treatment than patients without hydrocephalus. Hydrocephalus in medulloblastoma patients is most commonly due to blockage of CSF within the ventricular system as a result of the tumor mass. Tumors located in the posterior fossa frequently compress the 4 th ventricle, a phenomenon that contributes to the development of hydrocephalus (Crawford et al., 2007). The accumulation of CSF in the ventricular system increases ICP, a phenomenon that may exert negative effects on neuropsychological functioning by way of direct structural damage to the developing brain. Raised ICP has been shown to produce mechanical stress that decreases cerebral blood flow, thereby reducing the availability of neurotransmitters, damaging axons and myelin, and resulting in neuronal dysfunction (Del Bigio, 1993, Mataro et al., 2001). A position emission tomography (PET) study in infants with hydrocephalus demonstrated considerable hypoperfusion in brain regions surrounding the dilated lateral ventricles, including the frontal, parietal and visual association cortices (Shirane et al., 1992). Intellectual functioning is negatively affected by several factors that result directly from hydrocephalus, most notably the size of the ventricles, displacement of brain structures, and the degree of myelination (Fletcher et al., 1992, Mataro et al., 2001). Treatment with CSR has been

54 43 correlated with decreased white matter integrity and deficits in neuropsychological processes associated with white matter such as processing speed and working memory (Mabbott et al., 2008, Law et al., 2011). Thus, patients with hydrocephalus may receive several independent, yet cumulative, insults to white matter, a unique situation that may render them particularly vulnerable to neuropsychological deficits following treatment. It is therefore not surprising that patients with hydrocephalus in our medulloblastoma sample had lower baseline scores and larger declines on measures of neuropsychological functioning than patients without hydrocephalus. Prior to the development of valve shunting systems, it was not uncommon for children to die from untreated hydrocephalus (Hirsch, 1992). Shunting procedures significantly improved survival rates, and while shunting is clearly preferable to untreated hydrocephalus, shunt placement increases the risk of post-operative complications (Mataro et al., 2001). Specifically, shunts have been associated with infection, seizures, migration of the catheter, shunt malfunction and shunt obstruction (Gopalakrishnan et al., 2012). The presence of additional complications following treatment increases the risk of cognitive impairment in patients with hydrocephalus, regardless of etiology, and in medulloblastoma patients (Mataro et al., 2001, Mabbott et al., 2008). Taken together, medulloblastoma patients appear to be uniquely disadvantaged with respect to their risk of developing and suffering from the negative effects of having hydrocephalus, a fragile situation that is compounded further by aggressive treatment with CSR. In light of the increased risk of poor neuropsychological functioning as a result of hydrocephalus, medulloblastoma patients who develop hydrocephalus at any point stand to benefit from increased neuropsychological monitoring. Our results suggest these assessments need not be exhaustive, as measures of intellectual functioning, academic achievement and visual motor functioning appear to be highly sensitive to decreases in functioning. Thus, in theory, routine testing could be easily implemented into a child s academic experience upon returning to school. While extra monitoring cannot preserve or help to regain any previously lost functioning, it can attempt to mitigate further declines by alerting patients and their caregivers to newly developing areas of difficulty, and by providing individualized coaching and directed academic support in response.

55 Medulloblastoma Subgroups Medulloblastoma subgroups have heterogeneous intellectual outcomes following treatment. This finding has different implications for each subgroup, owing most heavily to their varied survival profiles following treatment WNT Results from Aim 2 highlight that no subgroup is spared intellectual decline following treatment. This finding is particularly relevant for patients with WNT tumors given their favorable survival outcome. Hydrocephalus cannot account for the observed declines, as only 3 of the 12 WNT patients had hydrocephalus, indicating other treatment factors (i.e. surgery or CSR) could be responsible. In light of the >90% survival rate patients for with WNT medulloblastomas, recent clinical studies have recommended WNT patients be treated with lower doses of CSR, or that it be used at all (Taylor et al., 2012, ISPNO 2012). If CSR is principally responsible for the intellectual decline observed in WNT patients, they stand to benefit intellectually from therapy de-escalation. Despite the absence of a significant relationship between CSR dose and intellectual functioning in this study, results from Aim 1 and Aim 3 suggest treatment with a reduced dose and a TB boost may mitigate some of the intellectual declines Group 3 Group 3 had the most favorable intellectual outcome following treatment, performing better than Group 4 and SHH on several measures of intellectual functioning despite still experiencing declines. This optimistic finding about Group 3 comes in stark contrast to their poor long-term prognosis (Northcott et al., 2011, Taylor et al., 2012). Northcott and colleagues recently demonstrated that survival in Group 3 patients neared zero by 8 years post-diagnosis (Northcott et al., 2011). We did not have exhaustive longitudinal data in the order of 8 years post-diagnosis for our Group 3 patients, and the current status of patients in this group is unknown. However, only three Group 3 patients in our sample are known to have died. The intellectual functioning of Group 3 patients is encouraging, in particular their performance at early time points following treatment, which we can interpret with greatest certainty owing to the increased stability of the longitudinal model at early time points. Since survival is dismal for

56 45 Group 3 patients treated with current protocols, perhaps Group 3 patients would benefit from novel experimental therapies, aimed primarily at promoting survival, but with the added benefit of preserving their favorable intellectual functioning should the experimental treatment prove to be effective Group 4 Recent research has placed considerable emphasis on elucidating the genetic variations that contribute to individual differences in toxicity due to radiotherapy. Radiation results in DNA damage and alters the microenvironment by way of inflammatory cytokines, cell-cell interactions, infiltration of inflammatory cells, and through the induction of restorative processes (Barnett et al., 2009, West and Barnett, 2011, Haston, 2012). Thus, it is plausible genes responsible for DNA damage recognition, apoptosis and inflammation could differ between the subgroups and consequently impact a subgroup s response to radiation. Of the three subgroups (Group 4, Group 3 and SHH) included in the longitudinal growth curve modeling, Group 4 had the poorest intellectual outcome following CSR. The heterogeneity of neuropsychological functioning observed in Group 4, Group 3 and SHH patients cannot be attributed to differences in medical or treatment factors, and suggest there may be something inherent to the subgroups that predispose to better or worse outcome following treatment. Perhaps Group 4 patients harbor germline mutations, single-nucleotide polymorphisms (SNPs), copy number variations (CNVs) or other genetic characteristics that render them more susceptible to radiation-induced damage. Despite being the most prevalent medulloblastoma subgroup, Group 4 remains the most poorly understood (Northcott et al., 2012a). Attempting to explain the genetic characteristics of Group 4 medulloblastoma that could account for its poor outcome is beyond the scope of this thesis. However, an idea is proposed. Nuclear factor-kb (NF-kB) signaling is related to the transcription of pro-inflammatory cytokines and its activity is regulated by NF-kB inhibitor alpha (NFKBIA) (Tak and Firestein, 2001, Zhang et al., 2011). Intriguingly, NF-kB has recently been implicated in Group 4 medulloblastomas in that deletions affecting several regulators of the NFkB pathway, including NFKBIA, have been identified (Northcott et al., 2012a). Importantly, treatment with radiation activates NF-kB in both tumor and non-tumor cells (Hei et al., 2011). Thus, in theory, a comparatively heightened inflammatory response could ensue following CSR in Group 4 patients as a result of their compromised NF-kB regulatory system. Pro-inflammatory

57 46 cytokines and the subsequent generation of reactive oxygen species (ROS) are be directly neurotoxic and could exert negative effects on brain integrity and subsequent developing cognitive processes (Wong and Van der Kogel, 2004, Siu et al., 2012). Although speculative, this model serves to highlight how differences in genetic characteristics between medulloblastoma subgroups could translate into heterogeneous intellectual outcomes following treatment. A recent study by Northcott and colleagues demonstrated the overall survival probability for Group 4 (formerly Group D) patients was identical when patients were treated with standard and reduced dose CSR (Northcott et al., 2011). Group 4 s poor intellectual functioning following treatment and lack of increased survival with standard dose CSR treatment suggest patients in Group 4 stand to benefit intellectually from therapy de-escalation without an associated survival cost. The potential mitigation of intellectual decline following less aggressive treatment in Group 4 will be discussed in section SHH Qualitatively, it appears SHH patients have the most stable intellectual functioning following treatment, declining less than both Group 4 and Group 3 on several measures. It is plausible SHH medulloblastomas may harbor genetic characteristics that render them less susceptible to radiation-induced damage. In contrast to Group 4, a clear increase in survival was demonstrated for SHH patients treated with standard vs. reduced dose CSR (Northcott et al., 2011). In light of their comparatively stable intellectual functioning and increased survival associated with more aggressive treatment (Taylor et al., 2012), considerable modification to current SHH treatment protocols may not be warranted. 5.3 Treatment Intensity (CSR dose and boost field) While it is logical to assume that treatment with reduced dose CSR would be less damaging and translate into better intellectual functioning, several studies have failed to demonstrate this outcome (Ris et al., 2001, Mabbott et al., 2008). However, findings in these studies may have been confounded by boost field heterogeneity. Interestingly, a study that successfully demonstrated a preservation of intellectual functioning with reduced dose CSR treatment only included patients treated with focal conformal boosts (Mulhern et al., 2005). Analyses conducted in Aim 1 and Aim 3 on CSR dose and boost field yielded interesting

58 47 qualitative results worthy of discussion. Qualitative analysis suggests treatment with a higher CSR dose may contribute to poor intellectual functioning. Furthermore, receiving a lateral beam boost to the entire PF following reduced dose CSR may negate any preservation of intellectual functioning yielded by receiving a reduced dose All medulloblastoma patients Treatment intensity (i.e. CSR dose and boost field) did not significantly predict intellectual functioning in our entire medulloblastoma sample. Treatment with a reduced dose + TB boost appears to be associated with a more favorable intellectual functioning, but this finding is qualitative and as such interpretation remains speculative. The standard dose TB boost comparison group contained the least number of patients (n=9/23), and also had minimal longitudinal data, owing to the treatment shift occurring within the past 6 years. In contrast, sample sizes for the other two groups: 1) standard vs. reduced dose (n=41/48) and 2) standard dose + PF vs. reduced dose + PF (n=32/25) should have been large enough to detect significant differences had clear associations been present. Rather, these results suggest treatment with a reduced dose + PF boost doesn t yield considerably different effects on intellectual functioning than treatment with standard dose, yet it remains possible that treatment with a reduced dose + TB boost does. A potential example of the effect of treatment with reduced dose CSR and a boost to the TB in mitigating declines is the stable trajectories observed in WMI. The concept behind working memory (WM) suggests an underlying system is responsible for maintaining, manipulating and storing information in the absence of external availability (Baddeley, 2003). Namely, tests that assess WM examine the amount of information an individual can keep in mind over a short period of time (Baddeley, 2003). Neuropsychological, neuroimaging and electrophysiological studies have provided considerable evidence for the involvement of white matter, in addition to neocortical and hippocampal regions in WM (Mabbott et al., 2008, Law et al., 2011, Poch and Campo, 2012). A TB boost delivers considerably less radiation to the temporal lobes than a PF boost (Wolden et al., 2003), a phenomenon that could underlie the observed difference in WM by way of decreased radiation-induced damage to the hippocampus.

59 Group 4 We capitalized on the recent discovery of medulloblastoma subgroups to be the first to examine the effect of treatment intensity on intellectual functioning in a homogenous subsample of medulloblastoma. Previous studies may have missed the contribution of CSR dose on intellectual functioning as a result of medulloblastoma subgroup heterogeneity. Examining the effect of treatment intensity both within a single subgroup and within the entire medulloblastoma sample seemed to be the most comprehensive manner to elucidate the impact of CSR dose on intellectual functioning. Namely, if clear trends were to emerge in a single subgroup but not for the entire medulloblastoma sample, one could argue that future studies should examine the impact of treatment on intellectual functioning in a subgroup-specific manner to prevent significant findings from being overshadowed. Unfortunately, we were left with small sample sizes when our Group 4 sample was subdivided into the four different CSR dose and boost conditions. Specifically, of the Group 4 patient treated with a TB boost, we only had an n=6 for standard dose and an n=7 for reduced dose. Despite these small sample sizes, trends emerged that approached significance. Furthermore, the effect observed in Group 4 was far more pronounced than when the entire medulloblastoma sample was examined. This finding lends support to the notion that intellectual functioning might be best examined in a subgroup-specific manner to prevent inter-subgroup variability from obscuring the results. While speculative, our results suggest that treatment with reduced dose CSR and a TB boost may mitigate some of the intellectual decline observed following treatment. This finding is encouraging, and provides impetus for future studies on treatment intensity to be conducted using larger sample sizes, and in a subgroup-specific manner. 5.4 Limitations A few limitations to the current study should be noted. Firstly, despite having a large sample size (n=91), we became limited by small sample sizes when our sample was stratified by the demographic, medical and treatment factors. These small sample sizes precluded analysis in Group 3, SHH and WNT, but also reduced power in Group 4 and within our entire sample, particularly when subdivisions were made based on treatment intensity.

60 49 Secondly, baseline assessments were only conducted following treatment. This is particularly important considering the emphasis placed on elucidating the impact of treatment on neuropsychological functioning. Neuropsychological declines in children treated with CSR have been observed within the first 12 months, but can be delayed by 1 to 2 years (Radcliffe et al., 1992, Mulhern and Palmer, 2003, Palmer et al., 2010). Our results suggest patients with hydrocephalus would have demonstrated lower neuropsychological functioning had they been assessed prior to treatment. Patients will likely continue to be evaluated for the first time following treatment, thus future studies seeking to elucidate the effect of treatment on neuropsychological functioning could benefit from controlling for patients who presented with hydrocephalus. Thirdly, the current study could have benefited from the inclusion of controls (i.e. surgery-only patients). Several studies have demonstrated neuropsychological declines in patients treated with surgery alone (Levisohn et al., 2000, Ris et al., 2008), and controlling for surgery could have provided a clearer picture concerning the impact of medical and treatment factors examined. However, a control group would only have been relevant for Aim1, as almost all medulloblastoma patients are treated with CSR, and it would have been impossible to include surgery-only controls in the subgroup-specific analyses. Finally, the current study was limited by the use of several different tests and test versions to examine neuropsychological and intellectual functioning. Using a variety of tests was unavoidable because of the longitudinal nature of this study, but it is not ideal. While equivalency studies have been conducted between all test versions and between all families of tests, the different tests and versions have different normative means, and direct comparisons between the tests and versions should be made with caution. However, results from Aim 1 paralleled what others have shown in the literature and suggests our results can be interpreted with a good degree of certainty. 5.5 Future directions All medulloblastoma patents Based on the findings in this study, it would be interesting to examine the effects of CSR dose and boost field in patients without hydrocephalus. Hydrocephalus has a dramatic impact on

61 50 neuropsychological functioning, and a clearer picture regarding the neuropsychological impact of CSR dose and boost field would likely emerge if patients predisposed to poor neuropsychological functioning for other reasons were excluded from the analysis Subgroups In order to expand upon the subgroup specific findings in this study, it will be crucial to conduct subsequent studies with larger sample sizes. However, because medulloblastoma subgroups present to differing degrees in the population, it might only be possible to conduct such large scale studies in a collaborative manner, as is currently being done with the MAGIC (Medulloblastoma Advanced Genomics International Consortium). With larger sample sizes, it would be ideal to examine neuropsychological functioning in addition to simply intelligence in all subgroups. Intelligence measures are clearly sensitive to declines in functioning, and examining intelligence was a logical starting point for subgroup characterization. However, subgroup analyses would benefit from a more comprehensive assessment of brain function, which could be gleaned by using an array of neuropsychological tests. In light of the subgroup differences in intellectual functioning that emerged in this study, it would be interesting to examine genetic variations known to predispose to toxicity following radiotherapy and to examine their prevalence in the subgroups. It would also be interesting to revisit the tumor genetics of Group 4 patients in our sample to determine if NFKBIA deletions predict poor intellectual functioning. If a correlation was established, theoretically, Group 4 patients could be screened for this deletion prior to the commencement of treatment, a process that could serve to inform patients about their relative risk of intellectual morbidity following treatment. 5.6 Conclusion This thesis provides an in-depth assessment of neuropsychological and intellectual functioning in medulloblastoma patients, and assesses the contribution of several demographic, medical and treatment factors. The results from this thesis recapitulate what has been shown in the literature, and also presents several novel findings. The negative impact of hydrocephalus on neuropsychological functioning, both at baseline and over a prolonged period of time, was clearly documented in medulloblastoma

62 51 patients for the first time. The predisposition to poor neuropsychological functioning suggests patients with hydrocephalus could benefit from increased neuropsychological monitoring and individualized support. Medulloblastoma patients suffer tremendously from neuropsychological morbidity, a phenomenon that is visibly worsened by the presence of hydrocephalus. The implementation of strategies to prevent further declines in this particularly vulnerable population clearly warrants further examination. Moreover, establishing that patients with hydrocephalus perform more poorly than patients without hydrocephalus has direct implications for future studies aimed at elucidating the effects of treatment on neuropsychological functioning in medulloblastoma patients. Controlling for the presence of hydrocephalus might lend itself to the generation of a clearer picture regarding the direct impact of treatment intensity on neuropsychological functioning. This thesis also provides the first evidence that medulloblastoma subgroups differ in their intellectual functioning following treatment. This important finding comes at an appropriate time given the pending shift towards subgroup-specific therapy in the medical community. Findings in this thesis suggest subgroup-specific treatment protocols may be a suitable way to achieve optimal intellectual functioning in each subgroup without compromising survival.

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74 63 Appendices Group 4 Subject Extent of resection Clinical Risk Histology Hydrocephalus Chemotherapy Radiation Deceased CSR dose Boost Total Dose Boost Site 1 Gross total Average Classic - Baby POG Posterior Fossa - 2 Subtotal Average Classic Yes ICE Posterior Fossa - 3 Subtotal High Classic - ICE Posterior Fossa - 4 Gross total Average Classic Yes CCG Posterior Fossa - 5 Gross total Average Classic Yes CCG Posterior Fossa - 6 Subtotal High Classic Yes POG Posterior Fossa - 7 Gross total High Classic - CCG Posterior Fossa - 8 Gross total High Classic - SJMB Tumor Bed - 9 Gross total Average Classic Yes SJMB Tumor Bed - 10 Gross total High Classic Yes SJMB Tumor Bed Yes 11 Gross total Average Classic - SJMB Tumor Bed - 12 Gross total High LCA Yes SJMB Tumor Bed - 13 Gross total High Classic Yes SJMB Tumor Bed - 14 Gross total Average LCA - SJMB Tumor Bed - 15 Gross total Average Classic Yes SJMB Tumor Bed - 16 Gross total Average LCA Yes Abbr. POG Tumor Bed - 17 Gross total Average Classic Yes SJMB Tumor Bed - 18 Gross total High Desmoplastic - CCG Posterior Fossa - 19 Gross total Average Desmoplastic Yes POG Posterior Fossa - 20 Gross total Average Classic - CCG Posterior Fossa - 21 Subtotal Average Classic - CCG Posterior Fossa Yes 22 Subtotal High Classic - POG Posterior Fossa - 23 Gross total High Classic Yes POG Posterior Fossa - 24 Gross total Average Classic Yes CCG Posterior Fossa - 25 Gross total Average Classic Yes CCG Posterior Fossa - 26 Gross total Average Classic - CCG Posterior Fossa - 27 Gross total Average Classic - CCG Posterior Fossa - 28 Gross total Average Classic Yes CCG Posterior Fossa - 29 Gross total Average Classic - CCG Posterior Fossa - 30 Gross total Average Classic - COG - ACNS Posterior Fossa - 31 Gross total Average Classic - SJMB Tumor Bed - 32 Subtotal High Classic - ICE Posterior Fossa - 33 Gross total Average Classic - ICE Posterior Fossa Yes 34 Gross total Average Classic Yes CCG Posterior Fossa - 35 Gross total Average Classic Yes CCG Posterior Fossa - 36 Gross total Average Classic - POG Posterior Fossa - 37 Gross total Average Classic - CCG Posterior Fossa - 38 Subtotal Average Classic Yes SJMB Tumor Bed - 39 Gross total Average Classic Yes SJMB Tumor Bed - 40 Subtotal High LCA - ICE Posterior Fossa - 41 Gross total Average Classic - ICE Posterior Fossa - Appendix 1 Detailed medical information for Group 4 patients

75 64 Group 3 Subject Extent of resection Clinical Risk Histology Hydrocephalus Chemotherapy Radiation Deceased CSR dose Boost Total Dose Boost Site 42 Gross total Average Classic - CCG Posterior Fossa - 43 Gross total Average LCA - POG Posterior Fossa Yes 44 Gross total High Desmoplastic Yes COG Posterior Fossa - 45 Gross total High Classic - POG Posterior Fossa - 46 Gross total Average Classic - SJMB Tumor Bed - 47 Subtotal Average LCA - SJMB Tumor Bed - 48 Subtotal High Classic Yes SJMB Tumor Bed - 49 Subtotal Average LCA Yes SJMB Tumor Bed - 50 Gross total Average Classic Yes SJMB Tumor Bed - 51 Gross total Average Classic - COG - ACNS Posterior Fossa Yes 52 Gross total Average Classic Yes COG Tumor Bed - 53 Gross total High Classic Yes CCG Posterior Fossa - 54 Gross total Average LCA - POG Posterior Fossa - 55 Gross total Average Classic Yes CCG Posterior Fossa - 56 Gross total High LCA - POG Posterior Fossa - 57 Gross total High Classic - ICE Posterior Fossa - 58 Subtotal High Classic - Baby POG Posterior Fossa Yes 59 Gross total Average Classic Yes CCG Posterior Fossa Yes SHH Subject Extent of resection Clinical Risk Histology Hydrocephalus Chemotherapy Radiation Deceased CSR dose Boost Total Dose Boost Site 60 Gross total Average Desmoplastic Yes CCG Posterior Fossa - 61 Gross total High Desmoplastic Yes POG Posterior Fossa - 62 Gross total Average Desmoplastic Yes SJMB Tumor Bed - 63 Gross total Average Classic Yes SJMB Tumor Bed - 64 Subtotal High Classic Yes POG Posterior Fossa Yes 65 Gross total Average LCA - SJMB Tumor Bed Yes 66 Gross total Average Desmoplastic Yes MOPP n/a n/a n/a n/a - 67 Subtotal High Classic - POG Posterior Fossa - 68 Subtotal High Classic - CCG Posterior Fossa - 69 Gross total High Classic Yes COG n/a n/a n/a n/a - 70 Gross total Average Classic - n/a Posterior Fossa - 71 Gross total Average Desmoplastic - n/a Posterior Fossa - 72 Gross total Average LCA Yes POG Posterior Fossa Yes 73 Subtotal High Classic Yes POG Posterior Fossa - 74 Gross total High LCA - COG n/a Tumor Bed - 75 Gross total Average LCA Yes SJMB Tumor Bed - 76 Gross total Average Classic - n/a Posterior Fossa - 77 Gross total Average LCA Yes SJMB Tumor Bed Yes 78 Subtotal Average Classic Yes SJMB Tumor Bed - 79 Gross total Average Desmoplastic - n/a Posterior Fossa - WNT Subject Extent of resection Clinical Risk Histology Hydrocephalus Chemotherapy Radiation Deceased CSR dose Boost Total Dose Boost Site 80 Gross total Average Classic Yes SJMB Tumor Bed - 81 Gross total Average Classic Yes SJMB Tumor Bed - 82 Gross total Average Classic Yes SJMB Tumor Bed - 83 Gross total Average Classic - SJMB Tumor Bed - 84 Gross total High Classic - POG Posterior Fossa - 85 Gross total Average Classic - CCG Posterior Fossa - 86 Gross total Average LCA - SJMB Posterior Fossa - 87 Gross total Average Classic - SJMB Tumor Bed - 88 Gross total Average Classic - n/a Posterior Fossa - 89 Gross total Average Classic - n/a Posterior Fossa - 90 Gross total Average Desmoplastic - CCG Posterior Fossa - 91 Gross total Average Classic - SJMB Tumor Bed - Appendix 2 Detailed medical information for Group 3, SHH and WNT patients.

76 65 Supplementary Tables < 7.26 years > 7.26 years Comparisons Mean SE Mean SE Overall Group Mean Slope FSIQ PRI PSI * VCI WMI Table 1 Group means; p values for overall group and mean slope differences for measures of intellectual functioning when medulloblastoma patients were stratified by age at diagnosis. < 7.26 years (n=44); > 7.26 years (n=47). Table 2 - Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by age at diagnosis. All models presented are significant (i.e. p < 0.05). * p < 0.05 Gross total Subtotal Comparisons Mean SE Mean SE Overall Group Mean Slope FSIQ PRI PSI VCI WMI Table 3 Group means; p values for overall group and mean slope differences in measures of intellectual functioning when medulloblastoma patients were stratified by extent of tumor resection. Subtotal (n=17); gross total (n =74).

77 66 Table 4 - Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by extent of tumor resection. All models presented, with the exception of PR, are significant (i.e. p < 0.05) * p < 0.05 Hydrocephalus No Hydrocephalus Comparisons Mean SE Mean SE Overall Group Mean Slope Visual Immediate Visual Delayed Verbal Immediate Verbal Delayed General Memory Attention/Concentration * Learning Delayed Recognition Table 5 Group means; p values for overall group and mean slope differences for measures of memory when medulloblastoma patients were stratified by the presence/absence of hydrocephalus. Presence of hydrocephalus (n =43); absence of hydrocephalus (n=48).

78 67 Table 6 - Estimated intercepts and slopes for CMS memory measures in medulloblastoma patients stratified by the presence/absence of hydrocephalus. All models presented are significant (i.e. p < 0.05) * p < 0.05 Average Risk High Risk Comparisons Mean SE Mean SE Overall Group Mean Slope FSIQ PRI PSI VCI WMI Table 7 Group means; p values for overall group and mean slope differences for measures of intellectual functioning when medulloblastoma patients were stratified by clinical risk. Average risk (n=64); high risk (n=27).

79 68 Table 8 - Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by clinical risk. All models presented are significant (i.e. p < 0.05). * p < 0.05 Standard Reduced Comparisons Mean SE Mean SE Overall Group Mean Slope FSIQ PRI PSI VCI WMI Table 9 Group means; p values for overall group and mean slope differences for measures of intellectual functioning when medulloblastoma patients were stratified by CSR dose. Standard dose (n=41); reduced dose (n=48)

80 69 Table 10 - Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by CSR dose. All models presented are significant (i.e. p < 0.05). * p < 0.05 Standard - PF boost Reduced - PF boost Comparisons Mean SE Mean SE Overall Group Mean Slope FSIQ PRI PSI VCI WMI Table 11 Group means; p values for overall group and mean slope differences for measures of intellectual functioning when patients that received a boost to the entire PF were stratified by CSR dose. Standard dose PF boost (n=32); reduced dose PF boost (n=25). Table 12 - Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by radiation dose, when field was kept consistent (i.e. PF boost). All models presented are significant (i.e. p < 0.05). * p < 0.05 Standard - TB boost Reduced - TB boost Comparisons Mean SE Mean SE Overall Group Mean Slope FSIQ PRI PSI VCI WMI

81 70 Table 13 Group means; p values for overall group and mean slope differences for measures of intellectual functioning when patients that received a boost to the TB were stratified by CSR dose. Standard dose TB boost (n=9); reduced dose TB boost (n=23). Table 14 - Estimated intercepts and slopes for measures of intellectual functioning in medulloblastoma patients stratified by radiation dose, when field was kept consistent (i.e. TB boost). The models presented are not significant (i.e. p > 0.05).

82 71 Table 15 - p values for overall group and mean slope differences for measures of intellectual functioning when patients were stratified by medulloblastoma subgroup. Group 4 (n=41); Group 3 (n=18); SHH (n=20) Table 16 Group means; p values for overall group and mean slope differences for measures of intellectual functioning when Group 4 patients were stratified by CSR dose. Standard dose (n=20); reduced dose (n=21). Table 17 - Estimated intercepts and slopes for measures of intellectual functioning in Group 4 patients stratified by radiation dose. All models presented, except VCI and WMI, are significant (i.e. p < 0.05). * p < 0.05