Original Article. Ting-Chi Yeh

Treatment of Childhood Acute Lymphoblastic Leukemia With Delayed First Intrathecal Therapy and Omission of Prophylactic Cranial Irradiation: Results of the TPOG-ALL-2002 Study Ting-Chi Yeh 1 ; Der-Cherng Liang* 1 ; Jen-Yin Hou 1 ; Tang-Her Jaing 2 ; Dong-Tsamn Lin 3 ; Chao-Ping Yang 2 ; Ching-Tien Peng 4,5 ; Iou-Jih Hung 2 ; Kai-Hsin Lin 3 ; Chih-Cheng Hsiao 6 ; Shiann-Tarng Jou 3 ; Shyh-Shin Chiou 7 ; Jiann-Shiuh Chen 8 ; Shih-Chung Wang 9 ; Te-Kau Chang 10 ; Kang-Hsi Wu 4 ; Jiunn-Ming Sheen 6 ; Hsiu-Ju Yen 11 ; Shih-Hsiang Chen 2 ; Meng-Yao Lu 3 ; Meng-Ju Li 3,12 ; Tai-Tsung Chang 13 ; Ting-Huan Huang 1 ; Yu-Hsiang Chang 14 ; Shu-Huey Chen 15 ; Yung-Li Yang 3 ; Hsiu-Hao Chang 3 ; Bow-Wen Chen 16 ; Pei-Chin Lin 7 ; Chao-Neng Cheng 8 ; Yu-Hua Chao 17 ; Shang-Hsien Yang 18 ; Yu-Mei Y. Chao 19 ; and Hsi-Che Liu 1 BACKGROUND: To eliminate cranial irradiation (CrRT) related sequelae and to minimize the adverse impact of traumatic lumbar puncture (TLP) with blasts, the Taiwan Pediatric Oncology Group (TPOG) introduced a modified central nervous system (CNS) directed regimen characterized by delayed triple intrathecal therapy (TIT) and the omission of CrRT for all children with newly diagnosed acute lymphoblastic leukemia (ALL). METHODS: This study compared the treatment outcomes of patients overall and patients with a non CNS-1 status (CNS-2, CNS-3, or TLP with blasts) in 2 treatment eras, one before and another after the revision of the TPOG-ALL-2002 protocol by the introduction of the modification (era 1 [2002-2008] with CrRT and era 2 [2009-2012] with delayed first TIT and no CrRT). RESULTS: There were no statistically significant differences in major outcomes between the 903 patients treated in era 1 and the 444 patients treated in era 2: the 5-year event-free survival (EFS) rates were 75.7% ± 1.4% and 72.1% ± 2.4%, respectively (P =.260), and the cumulative risks of isolated CNS relapse were 4.0% ± 0.7% and 4.1% ± 1.0%, respectively (P =.960). There were also no differences between non CNS-1 patients treated in era 1 (n = 76) and era 2 (n =28): the 5-year EFS rates were 52.3% ± 5.8% and 62.9% ± 9.4%, respectively (P =.199), and the cumulative risks of isolated CNS relapse were 6.3% ± 3.1% and 3.6% ± 3.5%, respectively (P =.639). Notably, TLP with blasts was completely eliminated after the first TIT was delayed in era 2. CONCLUSIONS: The delay of the first TIT until the clearance of circulating blasts and the total omission of CrRT did not compromise survival or CNS control in patients with childhood ALL, including those with a non CNS-1 status. Cancer 2018;000:000-000. 2018 American Cancer Society. KEYWORDS: acute lymphoblastic leukemia, central nervous system, children, cranial irradiation, intrathecal chemotherapy INTRODUCTION Cranial irradiation (CrRT), once a standard central nervous system (CNS) directed therapy for childhood acute lymphoblastic leukemia (ALL), has increasingly been omitted from protocols because of its many recognized complications, including second cancers (especially brain tumors), a decreased intelligence quotient, cognitive deficits, and Corresponding author: Hsi-Che Liu, Division of Pediatric Hematology-Oncology, Mackay Memorial Hospital, No. 92, Section 2, Chung-San North Road, Taipei 10449, Taiwan; hsiche@mmh.org.tw 1 Division of Pediatric Hematology-Oncology, Mackay Memorial Hospital and Mackay Medical College, Taipei, Taiwan; 2 Department of Hematology-Oncology, Chang Gung Children s Hospital Linkou and Chang Gung University, Taoyuan, Taiwan; 3 Department of Pediatrics, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan; 4 Division of Pediatric Hematology and Oncology, China Medical University Children s Hospital, Taichung, Taiwan; 5 Department of Biotechnology, Asia University, Taichung, Taiwan; 6 Department of Pediatrics, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan; 7 Department of Pediatrics, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan; 8 Department of Pediatrics, National Cheng Kung University Hospital, Tainan, Taiwan; 9 Department of Pediatrics, Changhua Christian Hospital, Changhua, Taiwan; 10 Department of Pediatrics, Taichung Veterans General Hospital, Taichung, Taiwan; 11 Department of Pediatrics, Taipei Veterans General Hospital and National Yang-Ming University, Taipei, Taiwan; 12 Department of Pediatrics, National Taiwan University Hospital Hsin Chu Branch, Hsinchu, Taiwan; 13 Department of Pediatrics, Chia-Yi Christian Hospital, Chiayi, Taiwan; 14 Department of Pediatrics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; 15 Department of Pediatrics, Taipei Medical University Shuang Ho Hospital, Taipei, Taiwan; 16 Division of Pediatric Hematology and Oncology, Koo Foundation Sun Yat-Sen Cancer Center, Taipei, Taiwan; 17 Department of Pediatrics, Chung Shan Medical University Hospital, Chung Shan Medical University, Taichung, Taiwan; 18 Department of Pediatrics, Buddhist Tzu Chi General Hospital, Hualien, Taiwan; 19 Childhood Cancer Foundation, Taipei, Taiwan *Deceased. Additional supporting information may be found in the online version of this article. We thank the data managers of the Biostatistical Center of the Childhood Cancer Foundation (Taiwan) for their assistance and Fang-Ju Sun (Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan) for assistance with the statistical analysis. We dedicate this article to the memory of Professor Der-Cherng Liang. DOI: 10.1002/cncr.31758, Received: May 9, 2018; Revised: June 25, 2018; Accepted: July 6, 2018, Published online Month 00, 2018 in Wiley Online Library (wileyonlinelibrary.com) 1

endocrinopathy. 1 4 The most recent protocols for ALL limit the use of prophylactic CrRT to 0% to 33% of childhood ALL patients. 5,6 To abolish CrRT-related sequelae and minimize the adverse prognostic impact of traumatic lumbar puncture (TLP) with blasts, beginning in 1999, we conducted a single-institution study at Mackay Memorial Hospital to modify CNS-directed therapy with delayed triple intrathecal therapy (TIT) upon the clearance of circulating blasts or up to 10 days after multidrug induction and with the omission of CrRT for all risk groups with newly diagnosed ALL. 7 We reasoned that the delayed intrathecal therapy approach would reduce the proportion of patients having TLP with blasts, an adverse risk feature associated with poor event-free survival (EFS) and an increased risk of CNS relapse. 8 Among the 152 patients treated in the Mackay study, the estimated 5-year EFS and overall survival (OS) rates (presented as mean ± standard error) were 84.2% ± 3.0% and 90.6% ± 2.4%, respectively. There were no isolated CNS relapses, and only 2 patients had combined CNS relapses. The 7-year cumulative risk of any CNS relapse was 1.4% ± 1.0%. Hence, the Mackay study improved CNS control and survival without compromising the systemic control of leukemia, and it enhanced the quality of life of patients by omitting the use of prophylactic CrRT. 7 These results led us to revise the protocol of a multi-institutional study (Taiwan Pediatric Oncology Group Acute Lymphoblastic Leukemia 2002 [TPOG-ALL-2002]) to add this modified CNS treatment in January 2009. A comparison of overall treatment outcomes between patients treated in the early era with prophylactic CrRT and patients treated in the recent era with delayed intrathecal therapy and the omission of prophylactic CrRT has been previously reported. 9 We now provide additional analysis with longer follow-up and show that the modified CNS treatment also did not compromise the outcomes of patients with a non CNS-1 status in this groupwide study. MATERIALS AND METHODS Patients From 2002 to 2012, all children in Taiwan with newly diagnosed ALL (0-18 years old) were enrolled in the TPOG-ALL-2002 study. Those with B-precursor ALL were stratified into standard-risk (SR), high-risk (HR), and very high-risk (VHR) groups according to their age, leukocyte count, cytogenetics, and molecular analysis at diagnosis. Patients with T-cell ALL were considered part of the VHR group. Details of the risk stratification and treatment regimens were previously published 7,9,10 (see the supporting information). All protocols were approved by the institutional review boards of the participating institutions. Written informed consent was obtained from the patients, parents, or guardians. CNS-Directed Therapy The CNS status was defined as follows: CNS-1, no blasts in a nontraumatic sample; CNS-2, fewer than 5 leukocytes per microliter with blasts in a nontraumatic sample; CNS-3, 5 or more leukocytes per microliter with blasts in a nontraumatic sample or the presence of cranial nerve palsy; and TLP, 10 or more erythrocytes per microliter with or without blasts. 11 Since January 2009, diagnostic lumbar puncture and the first TIT injection were not performed until blasts were no longer detectable in peripheral blood, but they were performed no later than 10 days after the initiation of induction therapy. Exceptions were made for patients who presented with cranial nerve palsy or other evidence of CNS disease; in these cases, lumbar puncture and the first TIT dose were administered on the day of diagnosis. SR patients with cranial nerve palsy, detectable blasts in peripheral blood on day 8, or a CNS-3 status were classified as HR. SR patients with CNS-1 received 14 doses of TIT, whereas those with CNS-2 or TLP with blasts received 2 additional TIT induction therapy and another 3 during maintenance therapy for a total of 19 doses. In the HR group, those with CNS-1 were given 17 doses of TIT; this escalated to 25 doses for those with CNS-2, CNS-3, or TLP with blasts, including 2 doses during induction and 6 during maintenance therapy. Before 2009, 18 Gy of CrRT was introduced prophylactically to VHR patients with a CNS-1 status at the beginning of maintenance therapy, and this was coupled with 5 concomitant TIT treatments; those younger than 2 years were excluded and were given TIT instead. VHR patients with CNS-2, CNS-3, or TLP with blasts at diagnosis received TIT weekly during induction until cerebrospinal fluid (CSF) remission was achieved and then once every 4 weeks during maintenance therapy before 24 Gy of CrRT. Among SR and HR patients, only those with refractory CNS leukemia at diagnosis (i.e., a failure to clear CSF blasts after 3 consecutive TIT treatments) received 24 Gy of CrRT with 5 concomitant TIT treatments at 1 year of remission. Since 2009, all patients have been treated with TIT alone without CrRT, and the doses and schedule of TIT have remained the same. The doses and timing of CNS-directed therapy by risk 2

Treatment Outcomes of Childhood ALL/Yeh et al TABLE 1. CNS-Directed Therapy According to Risk Group and CNS Status in 2 Treatment Eras CrRT TIT CNS-1: 14 doses Treatment Era 2002-2008 2009-2012 SR HR VHR SR HR VHR Only for refractory CNS leukemia at diagnosis and CNS relapse CNS-2, TLP with blasts: 19 doses; +2 induction and 3 maintenance CNS-1: 17 doses CNS-2/3, TLP with blasts: 25 doses; +2 induction and 6 maintenance At an age 2 y: 18 Gy plus 5 TIT treatments in 1st wk of maintenance; 24 Gy plus 5 TIT treatments for CNS-2/3 or TLP with blasts CNS-1: 10 doses before CrRT; if an age < 2 y at diagnosis, 10 doses and then every 8 wk before CrRT CNS-2/3, TLP with blasts: every week until CSF clear and then every 4 wk before CrRT; no TIT after CrRT Omission for all risk groups CNS-1: 14 doses CNS-1: 17 doses CNS-1: 19 doses CNS-2, TLP with blasts: 19 doses; +2 induction and 3 maintenance CNS-2/3, TLP with blasts: 25 doses; +2 induction and 6 maintenance CNS-2/3, TLP with blasts: every week until CSF clear; every 4 wk during maintenance Abbreviations: CNS, central nervous system; CrRT, cranial irradiation; CSF, cerebrospinal fluid; HR, high risk; SR, standard risk; TIT, triple intrathecal therapy; TLP, traumatic lumbar puncture; VHR, very high risk. CNS-1 indicates no blasts in a nontraumatic sample; CNS-2 indicates fewer than 5 white blood cells per microliter with blasts in a nontraumatic sample; CNS-3 indicates 5 or more white blood cells per microliter with blasts in a nontraumatic sample or the presence of cranial nerve palsy; and TLP indicates 10 or more red blood cells per microliter with or without blasts. group, CNS status, and treatment era are summarized in Table 1. In this trial, the correction of thrombocytopenia before intrathecal treatment, deep sedation during the procedure, and the practitioners most skilled at performing lumbar puncture were recommended. Statistical Analysis Differences between categorical variables were examined with Fisher s exact test or the chi-square test. The Kaplan-Meier method was used to estimate survival rates, with differences compared with the log-rank test. The duration of OS was defined as the time from diagnosis to the date of death. The duration of EFS was defined as the time from diagnosis to the date of failure (relapse, death, or the development of a second malignancy) or the last follow-up date for all patients who lacked an adverse event. Patients who did not achieve complete remission were considered to have an EFS of zero. Logistic regression analysis was used to estimate relative risk in the multivariate analysis. For patients who achieved complete remission, cumulative incidence functions of isolated CNS or any CNS relapse were estimated with the method of Kalbfleisch and Prentice. 12 An isolated CNS relapse was defined as one without simultaneous relapse at another site, and any CNS relapse was defined as CNS relapse accompanied or not by relapse in the bone marrow or any other extramedullary site. All reported P values were based on 2-sided tests, and they were considered statistically significant if they were less than.05. Data were analyzed with IBM SPSS software (release 21.0; IBM, Armonk, New York). RESULTS Altogether, 1366 patients were enrolled in the TPOG- ALL-2002 study. 9 Twelve patients in 2002-2008 (era 1) and 7 patients in 2009-2012 (era 2) were excluded because of an unknown CNS status. Thus, 903 patients in era 1 and 444 patients treated with delayed TIT and without CrRT in era 2 were included in this study for further analysis. The presenting features of the patients in the 2 eras were balanced. 9 In this study, the prevalence of patients with hyperdiploidy was relatively high and that of t(12;21) positivity was quite low among the patients tested (63% of the total patients; Table 2). There were no significant differences between the 2 eras in the rates of EFS (75.7% ± 1.4% vs 72.1% ± 2.4%; P =.260) 3

TABLE 2. Clinical and Biological Characteristics According to the CNS Status in 2 Treatment Eras Treatment Era 2002-2008 (With Irradiation) 2009-2012 (Delayed 1st TIT and Omission of Irradiation) Characteristic Total CNS-1 Non CNS-1 a P Total CNS-1 Non CNS-1 a P All, No. 903 c 827 76 444 d 416 28 Sex, No..53.11.64 Male 540 492 48 253 233 20 Female 363 335 28 191 183 8 Lineage.98.24.20 B 807 739 68 386 364 22 T 96 88 8 58 52 6 Age, median (IQR), y Age, No. 5.0 (3.1-9.4) 5.0 (3.2-9.3) 4.1 (1.7-10.1) 5.6 (3.0-11.3) 5.6 (3.0-11.3) 6.0 (3.5-12.9) <1 y 34 23 11 <.01 13 11 2.33.60 1-9 y 663 617 46 301 283 18 10 y 206 187 19 130 122 8 WBCs, median (IQR), 10 9 /L WBCs, No. 15.4 (4.7-53.1) 14.3 (4.5-47.7) 44.4 (11.9-177.4) 17.3 (5.1-75.4) 16.8 (5.0-69.8) 43.1 (10.0-161.4) 100 10 9 /L 774 724 50 <.01 349 330 19.15 1.00 >100 10 9 /L 129 103 26 95 86 9 Risk group, No. <.01 <.01.85 Standard 359 353 6 151 149 2 High 310 276 34 150 139 11 Very high 234 198 36 143 128 15 t(9;22), No. 550 e.70 296 e.60 1.00 Present 20 18 2 16 15 1 Absent 530 482 48 280 265 15 t(1;19), No. 550 e.79 296 e.30.59 Present 44 41 3 20 18 2 Absent 506 459 47 276 262 14 t(12;21), No. 550 e.24 296 e.71 1.00 Present 74 70 4 40 39 1 Absent 476 430 46 256 241 15 MLL-R, No. 550 e.02 296 e.27 1.00 Present 32 25 7 19 17 2 Absent 518 475 43 277 263 14 Hyperdiploidy, 550 e.50 296 e.31 1.00 No. f Present 112 100 12 49 45 4 Absent 438 400 38 247 235 12 Abbreviations: CNS, central nervous system; IQR, interquartile range; MLL-R, MLL gene rearrangement; TIT, triple intrathecal therapy; WBC, white blood cell. a Non CNS-1 indicates CNS-2, CNS-3, or traumatic lumbar puncture with blasts. b Comparison of non CNS-1 patients between the 2 eras. c Exclusion of 12 patients with an unknown CNS status. d Exclusion of 7 patients with an unknown CNS status. e Number of patients who were tested. f Fifty-one to sixty-eight chromosomes. P b 4

Treatment Outcomes of Childhood ALL/Yeh et al A B Figure 1. Treatment outcomes of era 1 (2002-2008 with cranial irradiation) and era 2 (2009-2012 with delayed first triple intrathecal therapy and no cranial irradiation): (A) 5-year overall survival and event-free survival in the 2 treatment eras and (B) cumulative incidence of any CNS relapse and isolated CNS relapse in the 2 treatment eras. The data are presented as means and standard errors. CNS indicates central nervous system. or OS (83.0% ± 1.3% vs 79.4% ± 2.1%; P =.069) or in the cumulative incidences of any CNS (6.3% ± 0.8% vs 5.4% ± 1.2%; P =.563) or isolated CNS relapse (4.0% ± 0.7% vs 4.1% ± 1.0%; P =.960; Fig. 1). There were also no significant differences in the cumulative incidence of relapse, isolated bone marrow relapse, or non-cns relapse between patients treated in the 2 treatment eras (Fig. 2). Clinical and Biological Features of Patients With a Non CNS-1 Status A total of 76 patients were classified as having a non CNS-1 status (i.e., CNS-2, CNS-3, or TLP with blasts) in era 1, and there were 28 in era 2. Their clinical and biological characteristics are summarized in Table 2. The clinical and biological characteristics did not differ significantly between non CNS-1 patients in the 2 treatment eras, and this suggests that delayed TIT did not select out higher risk patients with a non CNS-1 status. Among patients with non CNS-1 leukemia treated in era 1, the median age at diagnosis was 4.1 years (interquartile range [IQR], 1.7-10.1 years), and 11 patients were infants. The median leukocyte count was 44.4 10 9 /L (IQR, 11.9-177.4 10 9 /L), with 26 patients having counts greater than 100 10 9 /L. There were 68 patients with B-precursor ALL, and there were 8 patients with T-cell ALL. In comparison with the clinical features of CNS-1 patients, a younger age (<1 year), a higher 5

Figure 2. Cumulative incidence of relapse, isolated BM relapse, and non-cns relapse in treatment era 1 (2002-2008 with cranial irradiation) and treatment era 2 (2009-2012 with delayed first triple intrathecal therapy and no cranial irradiation). The data are presented as means and standard errors. BM indicates bone marrow; CNS, central nervous system. leukocyte count (>100 10 9 /L), an HR/VHR classification, and an MLL rearrangement showed a significant association with a non CNS-1 status; however, only an HR/VHR designation retained statistical significance in a multivariate analysis (odds ratio, 2.625; 95% confidence interval, 1.586-4.344; P <.001). In era 2, the median age at diagnosis was 6.0 years (IQR, 3.5-12.9 years), and 2 patients were infants. The median leukocyte count was 43.1 10 9 /L (IQR, 10.0-161.4 10 9 /L), with 9 patients having counts greater than 100 10 9 /L. There were 22 patients with B-precursor ALL, and there were 6 patients with T-cell ALL. As in era 1, the risk classification of HR/VHR was the only significant predictor of a non CNS-1 status in the multivariate model (odds ratio, 2.861; 95% confidence interval, 1.261-6.489; P =.012). Treatment Outcomes for Non CNS-1 Patients Treated in Different Eras The numbers of patients with CNS-2, CNS-3, and TLP with blasts were 35, 25, and 16, respectively, in era 1 and 19, 9, and 0, respectively, in era 2. Although there was no difference in the frequency of patients with CNS-2 or CNS-3 between the 2 eras (60 of 903 patients vs 28 of 444 patients; P =.810), the classification of TLP with blasts was completely eliminated after the first TIT treatment was delayed in era 2. The 5-year EFS and OS rates among non CNS-1 patients treated in era 1 were 52.3% ± 5.8% and 61.8% ± 5.7%, respectively. The cumulative risk estimates for any CNS or isolated CNS relapse were 17.3% ± 4.8% and 6.3% ± 3.1% at 5 years, respectively. The 5-year EFS for this group after modified treatment in era 2 was 62.9% ± 9.4%, whereas the OS was 77.9% ± 8.0%; the cumulative risk estimates for any CNS relapse and isolated CNS relapse were both 3.6% ± 3.5%. Importantly, these comparisons between treatment eras (Table 3 and Fig. 3) did not show any statistically significant differences that would indicate a loss of efficacy due to the delay in the first TIT treatment and the omission of CrRT altogether. Instead, the cumulative rates of CNS relapse were uniformly lower in era 2 than era 1 (Table 3), and the only relapse after treatment modification occurred 8 months after remission. DISCUSSION In this study, we show that modified CNS-directed therapy with delayed administration of the first TIT treatment and total omission of CrRT did not compromise the outcomes of treatment for childhood ALL, even when the analyses were limited to patients with a non CNS-1 status. Our results are in line with previous studies showing that CrRT can be successfully omitted for all risk groups of childhood ALL in the context of effective systemic chemotherapy and intrathecal therapy. 13,14 It should be noted that our results were obtained with a relatively high number of TIT treatments (14-19 doses in 6

Treatment Outcomes of Childhood ALL/Yeh et al TABLE 3. Treatment Outcomes According to the CNS Status in 2 Treatment Eras Non CNS-1 Status No. (%) a 5-y EFS, Mean ± SE, % 5-y OS, Mean ± SE, % 5-y Any CNS Relapse, Mean ± SE, % (No. of Relapses) 5-y Isolated CNS Relapse, Mean ± SE, % (No. of Relapses) Treatment Era 1: 2002-2008 (With Irradiation) Total 76 (8.4) 52.3 ± 5.8 61.8 ± 5.7 17.3 ± 4.8 (11) 6.3 ± 3.1 (4) CNS-2 35 (3.9) 66.8 ± 8.2 78.9 ± 7.1 10.0 ± 5.5 (3) 0 CNS-3 25 (2.8) 41.8 ± 10.1 54.3 ± 10.2 24.7 ± 9.9 (5) 20.5 ± 9.5 (4) TLP with blasts 16 (1.8) b 37.5 ± 12.1 37.5 ± 12.1 24.6 ± 12.6 (3) 0 Treatment Era 2: 2009-2012 (Delayed 1st TIT and Omission of Irradiation) Total 28 (6.3) 62.9 ± 9.4 77.9 ± 8.0 3.6 ± 3.5 (1) 3.6 ± 3.5 (1) CNS-2 19 (4.3) 62.0 ± 11.4 73.0 ± 10.4 5.3 ± 5.1 (1) 5.3 ± 5.1 (1) CNS-3 9 (2.0) 66.7 ± 15.7 88.9 ± 10.5 0 0 TLP with blasts 0 b ND ND ND ND Abbreviations: CNS, central nervous system; EFS, event-free survival; ND, not done; OS, overall survival; SE, standard error; TIT, triple intrathecal therapy; TLP, traumatic lumbar puncture. a Percentages are based on the total number of patients (903) in era 1. b Statistically significant between the 2 treatment eras. c Percentages are based on the total number of patients (444) in era 2. SR patients, 17-25 doses in HR patients, and 19-30 doses in VHR patients), 4 courses of high-dose methotrexate (at 2.5 g/m 2 in SR patients and at 5 g/m 2 in HR/VHR patients), and large cumulative doses of dexamethasone (1120 mg/m 2 in SR patients, 1620 mg/m 2 in HR patients, and 882 mg/m 2 in VHR patients). Vora et al 6 analyzed the impact of CrRT on clinical outcomes among patients treated in 10 major collaborative studies of childhood ALL with substantial differences in the proportions of patients receiving CrRT, which ranged from 0% to 33%. Their meta-analysis identified patients with CNS-3 at diagnosis as the only subgroup with a reduction in the rate of any or isolated CNS relapses after CrRT, but there were no significant differences in the cumulative risk of any adverse events or in survival between patients with a CNS-3 status treated with or without CrRT. They concluded that the use of prophylactic CrRT did not have an important impact on the risk of treatment outcomes in almost all subgroups of ALL treated with contemporary protocols. The reported rates of CNS-2 and CNS-3 leukemia in children have ranged from 5.4% to 32.2% and from 1.6% to 4.7%, respectively, 5,6 with EFS and OS rates for patients with CNS disease ranging from 43% to 86% and from 64% to 95%, respectively, depending on whether infants or patients with a CNS-2 status or TLP with blasts were enrolled. 5,6,8,13 28 In the TPOG-ALL-2002 study, the incidence rates for CNS-2 and CNS-3 involvement were similar to those cited previously and did not change significantly from one treatment era to the next. Treatment outcomes in patients with a CNS-2 or CNS-3 status were also comparable to results obtained in contemporary trials that adopted the same definition of CNS status. 8,14 17,24,28 In fact, in our study, non CNS-1 patients in era 2 tended to have better EFS and OS than those in era 1 (Fig. 3A), and this suggests that the delay in TIT actually could improve outcomes. In addition, the advances in supportive care, especially with the prophylactic use of antibiotics and antifungals, 29 the decrease in dropout rates, and the wide coverage of National Health Insurance in Taiwan also might have contributed to the trend of outcome improvements in era 2. Notably, the EFS of patients with a non CNS-1 status was inferior to that of CNS-1 patients only in era 1 (P <.001) and not in era 2 (P =.115). TLP with blasts has been reported to occur in 5.6% to 14.5% of patients with childhood ALL if the first puncture is performed at the time of diagnosis. 5,14,30 TLP contaminated with blasts has also been shown to be a risk factor for CNS relapse. 8 Several studies have reported EFS rates ranging from 56% to 81%. 5,8,14 17,28,31 Importantly, in our study, the modification of delaying the first TIT treatment eliminated the occurrence of TLP with blasts altogether. The other advantages of delaying the initial intrathecal therapy include the avoidance of sedation of patients with a mediastinal mass at diagnosis and the elimination of the potential toxicities of delayed clearance of methotrexate in patients with acute kidney injury because they are not exposed to methotrexate, which is a major component of intrathecal therapy. The outcomes of CNS involvement in ALL patients with a non CNS-1 status are not routinely reported. 7

A B Figure 3. Treatment outcomes of patients with a non CNS-1 status (CNS-2, CNS-3, or traumatic lumbar puncture with blasts) in era 1 (2002-2008 with cranial irradiation) and era 2 (2009-2012 with delayed first triple intrathecal therapy and no cranial irradiation): (A) 5-year overall survival and event-free survival in the 2 treatment eras and (B) cumulative incidence of any CNS relapse and isolated CNS relapse in the 2 treatment eras. The data are presented as means and standard errors. CNS indicates central nervous system. Pui and Howard 5 reviewed this issue and showed that the risk of any CNS relapse at 5 years ranges from 2.3% to 20.2% for CNS-2, from 10% to 33.3% for CNS-3, and from 8.0% to 9.1% for TLP with blasts. In a recent Children s Oncology Group study of patients with SR and HR B-cell ALL, the 5-year any CNS relapse rate was 5.6% for patients with a CNS-2 status and 5.1% for those with a CNS-3 status who received 18 Gy of CrRT; this was significantly higher than the 2.0% for patients with a CNS-1 status. 27 In the current study, the 5-year cumulative risk for any CNS relapse in non CNS-1 patients decreased from 17.3% in era 1 to 3.6% in era 2. Furthermore, the Mackay study in Taiwan 7 continued to enroll a total of 187 newly diagnosed patients between 1999 and 2012. All the lumbar puncture and TIT procedures were performed by the most skillful practitioners in our division. In this cohort, only a single infant had a CNS-2 status, and none had CNS-3 involvement or TLP with blasts. As of December 31, 2015, there were only 4 patients with any type of CNS relapse and 1 patient with an isolated CNS relapse. The 5-year EFS and OS rates and cumulative rates of any and isolated CNS relapse were 84.5% ± 2.7%, 91.8% ± 2.0%, 2.3% ± 2.1%, and 0.6% ± 0.6%, respectively (Fig. 4). No SR patients 8

Treatment Outcomes of Childhood ALL/Yeh et al Figure 4. Treatment outcomes of a single-institution study enrolling a total of 187 newly diagnosed patients between 1999 and 2012 at Mackay Memorial Hospital. The 5-year overall survival and event-free survival and the cumulative incidence of any CNS relapse and isolated CNS relapse are shown. The data are presented as means and standard errors. CNS indicates central nervous system. needed to be upgraded to HR because of a CNS-3 status or TLP with blasts. The advances in supportive care, especially the use of prophylactic antibiotics and antifungals, 29 and better compliance with the treatment protocol have additional positive impacts on the improvement of the treatment outcomes in this single-institution study. Altogether, these findings were pivotal in shaping the design of the nationwide TPOG-ALL-2002 study because they suggested the feasibility of a favorable outcome with a delayed first TIT injection, less intensive systemic chemotherapy, and uniform omission of CrRT, which could be expected to benefit patients. In conclusion, a delay of the first TIT procedure until the clearance of circulating blasts together with the complete omission of CrRT did not compromise either the survival or the control of CNS leukemia for children with ALL, including those with a non CNS-1 status. In the longer term, the omission of CrRT for all patients should lead to much lower rates of second cancers and cognitive deficits. FUNDING SUPPORT This work was supported by grants from Mackay Memorial Hospital, Taipei, Taiwan (MMH-E-106-09 and MMH-E-107-09), and the Ministry of Science and Technology, Taipei, Taiwan (MOST 106-2314-B-195-011-MY3). CONFLICT OF INTEREST DISCLOSURES The authors made no disclosures. AUTHOR CONTRIBUTIONS Ting-Chi Yeh: Conceptualization, methodology, formal analysis, investigation, patient contribution, data checking, writing original draft, and writing review and editing. Der-Cherng Liang: Conceptualization, methodology, validation, formal analysis, investigation, patient contribution, writing original draft, writing review and editing, and supervision. Jen-Yin Hou: Methodology, formal analysis, patient contribution, data checking, writing original draft, and writing review and editing. Tang-Her Jaing: Patient contribution and writing review and editing. Dong-Tsamn Lin: Patient contribution and writing review and editing. Chao-Ping Yang: Patient contribution and writing review and editing. Ching-Tien Peng: Patient contribution and writing review and editing. Iou-Jih Hung: Patient contribution and writing review and editing. Kai-Hsin Lin: Patient contribution and writing review and editing. Chih-Cheng Hsiao: Patient contribution and writing review and editing. Shiann-Tarng Jou: Patient contribution and writing review and editing. Shyh-Shin Chiou: Patient contribution and writing review and editing. Jiann-Shiuh Chen: Patient contribution and writing review and editing. Shih-Chung Wang: Patient contribution and writing review and editing. Te-Kau Chang: Patient contribution and writing review and editing. Kang-Hsi Wu: Patient contribution and writing review and editing. Jiunn-Ming Sheen: Patient contribution and writing review and editing. Hsiu-Ju Yen: Patient contribution and writing review and editing. Shih-Hsiang Chen: Patient contribution and writing review 9

and editing. Meng-Yao Lu: Patient contribution and writing review and editing. Meng-Ju Li: Patient contribution and writing review and editing. Tai-Tsung Chang: Patient contribution and writing review and editing. Ting-Huan Huang: Patient contribution and writing review and editing. Yu-Hsiang Chang: Patient contribution and writing review and editing. Shu-Huey Chen: Patient contribution and writing review and editing. Yung-Li Yang: Patient contribution and writing review and editing. Hsiu-Hao Chang: Patient contribution and writing review and editing. Bow-Wen Chen: Patient contribution and writing review and editing. Pei-Chin Lin: Patient contribution and writing review and editing. Chao-Neng Cheng: Patient contribution and writing review and editing. Yu-Hua Chao: Patient contribution and writing review and editing. Shang-Hsien Yang: Patient contribution and writing review and editing. Yu-Mei Y. Chao: Writing review and editing. 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Treatment Outcomes of Childhood ALL/Yeh et al Precis In this study, the delay of first triple intrathecal therapy until the clearance of circulating lymphoblasts and the total omission of cranial irradiation do not compromise survival or central nervous system control in childhood acute lymphoblastic leukemia, even when analyses are limited to patients with a"cns-1" is a common term to describe the CNS status in childhood acute lymphoblastic leukemia. I prefer to use "non-cns-1" or non-central nervous system (CNS)-1 status. 11