Therapy-Related Myelodysplastic Syndrome Morphologic Subclassification May Not Be Clinically Relevant

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1 Hematopathology / T-MDS SUBCLASSIFICATION Therapy-Related Myelodysplastic Syndrome Morphologic Subclassification May Not Be Clinically Relevant Zeba N. Singh, MD, 1 Dezheng Huo, PhD, 3 John Anastasi, MD, 1,4 Sonali M. Smith, MD, 2,4 Theodore Karrison, PhD, 3 Michelle M. Le Beau, PhD, 2,4 Richard A. Larson, MD, 2,4 and James W. Vardiman, MD 1,4 Key Words: Therapy-related leukemia; Therapy-related myelodysplasia; World Health Organization classification Abstract In practice, cases of therapy-related myelodysplastic syndrome (t-mds) are often classified according to morphologic schemes used for de novo MDS. However, there are few data addressing the appropriateness of such classification. We studied 155 patients with therapy-related acute myeloid leukemia (t- AML)/t-MDS to determine whether subclassification by the World Health Organization (WHO) criteria for de novo MDS provides prognostic information in t-mds. In addition, we assessed whether cytogenetic stratification by the International Prognostic Scoring System (IPSS) guidelines or karyotypic complexity was prognostically important. We found no differences in median survival times among patients classified into the different WHO subgroup of MDS or according to their bone marrow blast percentage; our results indicate a uniformly poor outcome in t-mds regardless of morphologic classification. However, significant survival differences correlated with cytogenetic stratification according to IPSS guidelines and/or karyotypic complexity. We found only a borderline difference in median survival of patients with an initial t-mds diagnosis compared with patients with an initial t-aml diagnosis. Numerous studies have documented the prognostic usefulness of the morphologic classification of de novo myelodysplastic syndromes (MDSs). 1-6 The subgroups of the French-American-British (FAB) 7,8 and the World Health Organization (WHO) 9 classification schemes for MDS correlate with overall survival and with the rate of transformation to overt acute leukemia. The prognostic impact of these schemes is not unexpected because the subgroups of each system are defined in part by the percentage of bone marrow blasts, which is itself an independent predictor of prognosis in de novo MDS. 10 The International Prognostic Scoring System (IPSS) generated by the International MDS Risk Analysis Workshop demonstrated that apart from the blast count and the number of peripheral blood cytopenias, stratification according to good-, intermediate-, and poor-risk cytogenetic abnormalities further separates patients with de novo MDS into distinct prognostic groups. 10 For patients with therapy-related MDS (t-mds), nomenclature has historically been a problem, and the value of morphologic subclassification and risk assignment by cytogenetic findings are not clear The FAB system made no distinction between de novo MDS and t-mds. 7,8 However, some authors reported it difficult to classify therapy-related disease by FAB criteria, mainly because many cases show marked multilineage dysplasia but fewer than 5% blasts in the blood or bone marrow, findings that do not fit well into any of the FAB subgroups Such cases could be classified by the WHO criteria as refractory cytopenia with multilineage dysplasia (RCMD), yet in that classification scheme, therapy-related acute myeloid leukemia (t-aml) and t-mds are simply grouped together as a single syndrome (t-aml/mds) and included with AML. 9 The WHO system further recognizes 2 subtypes of t-aml and t-mds Am J Clin Pathol 2007;127:

2 Singh et al / T-MDS SUBCLASSIFICATION depending on the previous chemotherapy received by the patient (alkylating agent related vs topoisomerase-ii inhibitor related disease). However, the WHO guidelines do not clearly state whether further subclassification of t-mds should be done using the same criteria as for de novo MDS or whether such classification is clinically relevant. Instead, they merely indicate these types of AML and MDS may be classified if appropriate in a specific morphologic or genetic category with the qualifying term, therapy-related. 9 In practice, pathologists and clinicians often use the same classification for t-aml and for t-mds that is used for their de novo counterparts, with the assumption that it provides prognostic information and that it can be used for treatment planning In the case of cytogenetic stratification, patients with t-mds were excluded from study at the International MDS Risk Analysis workshop, 10 and whether the cytogenetic risk groups as defined in the IPSS or other stratification methods are relevant to patients with t-mds has not been fully explored. It has been our impression that patients with t-mds have almost uniformly poor outcomes with rapid progression to acute leukemia or bone marrow failure regardless of the initial morphologic classification of their disease. To determine whether this was so, we took advantage of a well-studied cohort of patients with t-mds and asked whether subclassification of t-mds according to the WHO guidelines for de novo MDS was clinically useful and whether cytogenetic stratification has the same prognostic value for t-mds as for de novo MDS. Our results demonstrate that outcome has little relation to the morphologic subclassification in patients with t-mds but that cytogenetic stratification predicts outcome. Materials and Methods Cases The computerized patient files in the Section of Hematology/Oncology, University of Chicago, Chicago, IL, were searched for all cases diagnosed as t-aml or t-mds between July 1972 and July Of the 306 cases identified, the bone marrow specimen diagnostic for t-aml or t- MDS had been obtained at our institution in 166 cases, and in the remaining 140 cases, the diagnosis had been made on slides obtained from outside institutions. Our study was limited to the former group for whom the diagnostic bone marrow material was still available in our files for review. In 11 of these cases, the bone marrow specimens were inadequate, precluding morphologic assessment. These 11 cases were excluded from further analyses. Clinical and follow-up data were obtained from the clinical files and have been previously reported in detail. 25 Treatments given to patients after the development of t-mds/t-aml were individualized and variable in most cases, ranging from supportive care only to intensive chemotherapy and, rarely, bone marrow transplantation. Furthermore, treatment options varied considerably during the 30 years that cases were accrued for this study. Thus, response data were not assessed for this report. Treatment, however, was never based on the morphologic subclassification of MDS. Morphologic Evaluation of Specimens All diagnostic material, including peripheral blood, bone marrow aspirate, and bone core biopsy specimens, was reviewed by 3 of us (Z.N.S., J.A., and J.W.V.), and a 500-cell differential count was performed on the bone marrow aspirates to enumerate blasts and other cellular elements. The granulocytic, erythroid, and megakaryocytic lineages were considered dysplastic when 10% or more of the cells in the lineage showed unequivocal dyspoiesis. The core biopsy specimen was reviewed for cellularity, an estimated blast percentage, and reticulin fibrosis. In most cases, the blast percentage evaluated on the bone marrow aspirate smears agreed with the finding on the core biopsy specimen. In the few discrepant cases, the specimen with the higher blast count was considered more representative of the disease status. An iron stain (Perls Prussian blue) on the aspirate smear or clot section was reviewed in all cases, and ringed sideroblasts were enumerated as a percentage of the total erythroid component. The bone marrow was also assessed for involvement by the initial malignancy. By using the WHO classification system and the 20% blast threshold for a diagnosis of AML, we divided cases into those with an initial diagnosis of t-aml and those with an initial diagnosis of t-mds. The t-mds group was further subclassified according to the WHO guidelines for de novo MDS. Cytogenetic Analysis Cytogenetic analysis was performed with quinacrine fluorescence and trypsin-giemsa-banding techniques on bone marrow cells from aspirates or biopsy specimens and on peripheral blood cells obtained at the time of diagnosis. Metaphase cells were examined from direct preparations and from 24- or 48-hour unstimulated cultures. Chromosomal abnormalities are described according to the International System for Human Cytogenetic Nomenclature. Cases were grouped into the following cytogenetic subgroups: (1) as defined for prognostic evaluation of de novo MDS by the IPSS: good risk, ie, sole del(5q), sole del(20q), Y, or normal; poor risk, ie, complex ( 3 abnormalities) or abnormalities of chromosome 7; and intermediate risk, ie, all other abnormalities 10 ; and (2) according to the complexity of the cytogenetic abnormalities. Statistical Analysis Associations between categorical variables were analyzed by using the Fisher exact test. Kruskal-Wallis nonparametric 198 Am J Clin Pathol 2007;127: Downloaded 198 from

3 Hematopathology / ORIGINAL ARTICLE tests were used to compare latency intervals between groups. Overall survival rates were estimated by the Kaplan-Meier method, and comparisons between groups were performed using the log-rank test and the generalized Wilcoxon test for equality of survival functions. 26 The Wilcoxon test weights early deaths more than later deaths and, thus, is sensitive to early differences, whereas the log-rank weights all deaths equally. Hazard ratios and corresponding 95% confidence intervals were calculated from Cox proportional hazards model. P values of.05 or less were regarded as statistically significant. Results The study included 155 cases. The clinical features of the cases are similar to the larger group from which they were derived. 25 Briefly, 89 patients had a primary hematologic malignancy (Hodgkin lymphoma, 41; non-hodgkin lymphoma, 36; precursor B-lymphoblastic lymphoma, 1; light chain disease, 1; and multiple myeloma, 10), whereas 62 patients had nonhematologic malignancies, and 4 patients had received cytotoxic therapy for a nonneoplastic disease. Chemotherapy had been given to 129 patients. The majority of patients (70) received topoisomerase-ii inhibitors and alkylating or antimetabolite therapy; only 3 patients received topoisomerase-ii inhibitors as the single chemotherapeutic agent. Radiotherapy was given to 98 patients, and, of these, 25 received radiotherapy alone and 73 received combined modality therapy with radiotherapy and chemotherapy. Of the 155 cases, 81 (52.3%) initially were diagnosed as t-mds and 69 (44.5%) as t-aml. The remaining 5 (3.2%) cases had laboratory and morphologic features that overlapped MDS and myeloproliferative disorders (MPDs) and were designated as therapy-related MDS/MPD (t- MDS/MPD). There was no relationship between the type of primary disease and initial diagnosis as t-mds or t-aml. The average latency period from onset of therapy for the primary disorder to the development of bone marrow dysfunction was 62 months for t-mds and 63 months for t-aml. The latency period was not different between patients with primary hematologic malignancies and nonhematologic malignancies, nor was it different among patients who received chemotherapy only, radiotherapy only, or combined modality therapy. Table 1 shows the distribution of initial diagnoses in the 155 cases classified according to the WHO criteria. According to the WHO criteria for de novo MDS, 78 of 81 cases could be subclassified as follows: 6 as refractory anemia (RA), 29 as RCMD, 4 as RCMD and ringed sideroblasts (RCMD-RS), 19 as RA with excess blasts-1 (RAEB-1), and 20 as RAEB-2. Three cases with dysplastic features limited to one lineage other than erythroid or with insufficient numbers of dysplastic cells in multiple lineages Table 1 Distribution of Initial Diagnoses in 155 Patients With t-aml/ t-mds Classified According to WHO Criteria for De Novo MDS Initial Diagnosis No. (%) of Cases t-mds 81 (52.3) RA 6 RARS 0 RCMD 29 RCMD-RS 4 RAEB-1 19 RAEB-2 20 MDS-U 3 t-mds/mpd 5 (3.2) CMML 3 a-cml 1 MDS/MPD, unclassifiable 1 t-aml 69 (44.5) a-cml, atypical chronic myeloid leukemia; AML, acute myeloid leukemia; CMML, chronic myelomonocytic leukemia; MDS, myelodysplastic syndrome; MPD, myeloproliferative disorder; RA, refractory anemia; RAEB, refractory anemia with excess blasts; RARS, RA with ringed sideroblasts; RCMD, refractory cytopenia with multilineage dysplasia; RS, ringed sideroblasts; t, therapy-related; U, unclassified; WHO, World Health Organization. to qualify for multilineage dysplasia fell into the unclassified category (MDS-U). Of the 5 cases in the t-mds/mpd subgroup, 3 had chronic myelomonocytic leukemia, 1 had atypical chronic myeloid leukemia, and 1 had extreme thrombocytosis with ringed sideroblasts (MDS/MPD, unclassifiable). For the purpose of analysis, the t-mds and t-mds/mpd subgroups were combined, and hereafter are described as t-mds. Examination of the bone marrow aspirate smears and core biopsy specimens revealed persistent primary malignancy in 18 cases ranging from small foci of involvement to nearly 70% involvement of the marrow by the primary tumor. Cytogenetic Analysis Table 2 shows the overall distribution of cytogenetic abnormalities in the t-mds and t-aml cases. Except for the balanced translocations t(8;21), t(15;17), inv(16), and t(11q23), Table 2 Distribution of Cytogenetic Abnormalities in t-mds and t-aml Karyotype t-mds t-aml Normal 10 6 Abnormalities of chromosome 5, 7, or both 64 3 (with or without other abnormalities) 8 Balanced translocations 11 t(11q23) 6 t(8;21) 2 inv(16) 2 t(15;17) 1 Other abnormalities Complex karyotype ( 3 abnormalities) * Yes 41 (48%) 35 (51%) No 45 (52%) 34 (49%) AML, acute myeloid leukemia; MDS, myelodysplastic syndrome; t, therapy-related. * Data are given as number (percentage). Am J Clin Pathol 2007;127:

4 Singh et al / T-MDS SUBCLASSIFICATION abnormalities that by definition were found only in the t-aml category, the cytogenetic abnormalities (chromosome 5 and/or 7, other abnormalities, complex karyotype, and normal karyotype) were similarly distributed in the t-mds and t-aml groups. The majority (76/86 [88%]) of the t-mds cases had 1 or more cytogenetic abnormalities. Overall, abnormalities of chromosome 5 and/or 7 were most commonly observed (64/86 [74%]). Complex karyotypes ( 3 abnormalities) were observed in about half (41/86 [48%]) of the cases. When stratified within the good-, intermediate-, and poor-risk IPSS-cytogenetic categories, most t-mds cases (70%) had poor risk cytogenetic abnormalities, followed by the intermediate-risk (16%) and good-risk (14%) categories. Table 3 shows the distribution of cytogenetic abnormalities in the t-mds subgroups with respect to IPSS cytogenetic categories, the complexity of the karyotype, and the overall distribution of chromosome 5 and/or 7 abnormalities and other abnormalities vs normal karyotype. Survival All patients were followed up for at least 24 months or until death. By January 2005, 149 (96.1%) of the patients had died. Figure 1A shows there was no difference in the overall survival (OS) among the subgroups of t-mds (P =.78, Wilcoxon test; P =.54, log-rank test). Table 4 provides survival probabilities and hazard ratios for the 3 large subgroups of t-mds. The hazard of death was similar among the RCMD, RAEB-1, and RAEB-2 subgroups. To analyze whether the percentage of bone marrow blasts has similar prognostic importance in t-mds as proven in de novo MDS, cases with fewer than 5% and 5% or more bone marrow blasts were compared Figure 1B (Table 4). The survival times for the fewer than 5% and 5% or more blast categories were virtually identical (medians, 7.9 months and 8.7 months, respectively; P =.99, Wilcoxon test; P =.37, log-rank test). Relative to patients with fewer than 5% blasts, patients with 5% or more blasts had similar risks of dying (hazard ratio, 1.22; 95% confidence interval, ). The presence of the primary malignancy in the bone marrow at the time of the diagnosis of therapy-related disease did not impact the survival of patients in comparison with those in whom there was no tumor present (data not shown). The OS of patients with t-mds with cytogenetic abnormalities of chromosome 5 and/or 7 or other abnormalities vs a normal karyotype is depicted in Figure 2A. Patients with a normal cytogenetic pattern had borderline significantly better survival compared with patients with cytogenetic abnormalities (median survival time: chromosome 5/7 abnormalities, 7.6 months; others, 8.6 months; normal karyotype, 11.4 months) (P =.053, log-rank test; P =.18, Wilcoxon test). However, when analyzed according to the IPSS cytogenetic subgroups Figure 2B, there was a significant difference in median survival: good-risk subgroup, 11.4 months; intermediate-risk subgroup, 11.7 months; poor-risk subgroup, 7.1 months (P =.02, Wilcoxon test; P =.007, log-rank test). We also found that patients with t-mds with complex karyotypes had a shorter survival time (median, 5.5 months) than patients without complex karyotypes (11.7 months), and the difference was statistically significant (P <.001, Wilcoxon test; P =.001, log-rank test) Figure 2C. Of 86 cases of t-mds, 30 progressed to t-aml, and 27 remained as t-mds at the time of death. In the remaining 29 cases, information regarding progression to t-aml before death or last follow-up was not available. Among the cases Table 3 Distribution of Cytogenetic Abnormalities in t-mds Subgroups * t-mds Subgroup RA RCMD RCMD-RS MDS-U RAEB-1 RAEB-2 MPD/MDS (n = 6) (n = 29) (n = 4) (n = 3) (n = 19) (n = 20) (n = 5) Cytogenetic abnormality Abnormalities 5, 7, or both 2 (33) 19 (66) 4 (100) 2 (67) 17 (89) 17 (85) 3 (60) Other clonal abnormalities 1 (17) 6 (21) 0 (0) 1 (33) 1 (5) 2 (10) 1 (20) Normal 3 (50) 4 (14) 0 (0) 0 (0) 1 (5) 1 (5) 1 (20) Complex karyotype Yes 2 (33) 13 (45) 4 (100) 1 (33) 9 (47) 10 (50) 2 (40) No 4 (67) 16 (55) 0 (0) 2 (67) 10 (53) 10 (50) 3 (60) IPSS cytogenetic categories Good risk 3 (50) 4 (14) 0 (0) 0 (0) 2 (11) 1 (5) 2 (40) Intermediate risk 1 (17) 8 (28) 0 (0) 1 (33) 3 (16) 1 (5) 0 (0) Poor risk 2 (33) 17 (59) 4 (100) 2 (67) 14 (74) 18 (90) 3 (60) IPSS, International Prognostic Scoring System; MDS, myelodysplastic syndrome; MPD, myeloproliferative disorder; RA, refractory anemia; RAEB, refractory anemia with excess blasts; RCMD, refractory cytopenia with multilineage dysplasia; RS, ringed sideroblasts; t, therapy-related; U, unclassified. * Data are given as number (percentage). P =.053, log-rank test; P =.18, Wilcoxon test. P =.001, log-rank test; P <.001, Wilcoxon test. P =.02, log-rank test; P =.007, Wilcoxon test. 200 Am J Clin Pathol 2007;127: Downloaded 200 from

5 Hematopathology / ORIGINAL ARTICLE A B MDS-U (n = 3) MDS/MPD (n = 5) RA (n = 6) RAEB-1 (n = 19) RAEB-2 (n = 20) RCMD (n = 29) RCMD-RS (n = 4) Blasts <5% (n = 46) Blasts 5%-19% (n = 40) Figure 1 Overall survival in therapy-related myelodysplastic syndrome (t-mds) subgroups classified by the World Health Organization criteria for de novo MDS (A) and with <5% and 5%-19% bone marrow blasts (B). There is no statistically significant difference (A) in the median overall survival between the t-mds morphologic subgroups: refractory anemia (RA), 7.9 months; refractory cytopenia with multilineage dysplasia (RCMD), 8.5 months; RCMD with ringed sideroblasts (RCMD-RS), 3.9 months; refractory anemia with excess blasts (RAEB)-1, 5.5 months; RAEB-2, 9.3 months; MDS unclassified (MDS-U), 15.8 months; MDS/myeloproliferative disorder (MPD), 10.8 months (P =.54, log-rank test; P =.78, Wilcoxon test). Survival time is virtually identical (B) in t-mds with <5% bone marrow blasts (median, 7.9 months) and with 5%-19% blasts (median, 8.7 months) (P =.37, log-rank test; P =.99, Wilcoxon test). that progressed, the median time for progression from t-mds to t-aml was 5.3 months; the interquartile range (25th-75th percentiles) was 2.3 to 8.7 months. As shown in Table 5, there was no significant difference among the WHO subgroups of t-mds regarding progression to t-aml (P =.53). When survival was compared between t-mds and t- AML cases Figure 3A, there was no statistically significant difference in general (P =.19, log-rank test) and only a borderline significant difference between t-mds and t-aml in the early survival period (P =.043, Wilcoxon test). The median survival time was 8.5 months for patients with an initial diagnosis of t-mds compared with 6.5 months for patients with an initial diagnosis of t-aml. To avoid confounding the analysis by cases with balanced chromosomal translocations, which were exclusively within the t-aml group, we repeated the survival analysis after exclusion of this group Figure 3B. The difference between t-mds and t-aml was still significant (P =.038, Wilcoxon test; P =.012, log-rank test). Discussion The aims of this study were 2-fold. First, we wanted to apply the WHO criteria for classification of de novo MDS to cases of t-mds to determine whether morphologic classification has similar clinical relevance in t-mds as it does in Table 4 Overall Survival by WHO Subgroups and Percentage of Bone Marrow Blasts in t-mds Cases (%) 6-mo 1-y Hazard Ratio (95% CI) (95% CI) (95% CI) t-mds subgroup RCMD (n = 29) 66 (45-80) 38 (21-55) RAEB-1 (n = 19) 47 (24-67) 42 (20-62) 1.28 ( ) RAEB-2 (n = 20) 70 (45-85) 25 (9-45) 1.28 ( ) Bone marrow blasts (%) <5 (n = 46) 63 (47-75) 37 (23-51) 5-19 (n = 40) 60 (43-73) 33 (19-47) 1.22 ( ) CI, confidence interval; RAEB, refractory anemia with excess blasts; RCMD, refractory cytopenia with multilineage dysplasia; t-mds, therapy-related myelodysplastic syndrome. de novo disease. Second, we wanted to determine whether cytogenetic stratification according to the IPSS guidelines, which are proven to be predictive of outcome in de novo MDS, or according to karyotypic complexity could also be applied to t-mds. We addressed these questions by analyzing a well-studied cohort of t-mds cases. Our results suggest that morphologic subclassification by the WHO guidelines offers no prognostic information regarding disease progression or survival but that cytogenetic abnormalities are predictive of overall outcome. Am J Clin Pathol 2007;127:

6 Singh et al / T-MDS SUBCLASSIFICATION A B Normal (n = 10) Others (n = 12) Abnormal 5 and/or 7 (n = 64) Good risk (n = 12) Intermediate risk (n = 14) Poor risk (n = 60) C <3 Abnormalities (n = 45) 3 Abnormalities (n = 41) Figure 2 Overall survival (OS) of patients with therapyrelated myelodysplastic syndrome and a normal karyotype or cytogenetic abnormalities (chromosome 5 and/or 7 or others) (A), the International Prognostic Scoring System (IPSS) cytogenetic categories (B), and the complexity of the karyotype (C). Patients with a normal karyotype (A) have borderline significantly better survival than patients with cytogenetic abnormalities (P =.053, log-rank test; P =.18, Wilcoxon test). Patients in the IPSS poor-risk category (B) have a significantly shorter OS (P =.007, log-rank test; P =.02, Wilcoxon test). Patients with complex ( 3) abnormalities (C) have a shorter median survival time than patients with <3 abnormalities (P <.001, log-rank test; P =.001, Wilcoxon test). Patients with complex abnormalities (C) overlap with the poor-risk IPSS group (B) and have a similar median OS. Table 5 Follow-up and Progression to t-aml in WHO Subgroups of t-mds * t-mds Subgroup RA RCMD RCMD-RS MDS-U RAEB-1 RAEB-2 MPD/MDS (n = 6) (n = 29) (n = 4) (n = 3) (n = 19) (n = 20) (n = 5) t-mds to t-aml 1 (17) 6 (21) 3 (75) 1 (33) 8 (42) 10 (50) 1 (20) Progression unknown 3 (50) 11 (38) 0 (0) 1 (33) 6 (32) 5 (25) 3 (60) No progression 2 (33) 12 (41) 1 (25) 1 (33) 5 (26) 5 (25) 1 (20) AML, acute myeloid leukemia; MDS, myelodysplastic syndrome; MPD, myeloproliferative disorder; RA, refractory anemia; RAEB, refractory anemia with excess blasts; RCMD, refractory cytopenia with multilineage dysplasia; RS, ringed sideroblasts; t, therapy-related; U, unclassified. * Data are given as number (percentage). There was no difference in progression to t-aml among subgroups of t-mds (P =.53). In the present study, there were cases classified into all WHO subgroups except refractory anemia with ringed sideroblasts and the 5q syndrome, ie, MDS with isolated del(5q), categories. The largest single group was RCMD, which included 29 (34%) of the cases. There was no significant difference in OS or the incidence or rate of progression to t-aml among the WHO subgroups, indicating that morphologic subclassification is not of prognostic value in t-mds. These data for t-mds are in marked contrast with recently published studies that show WHO subgroups have prognostic significance for de novo MDS. 4-6 Because the WHO morphologic subgroups are defined largely by the percentage of blasts in the bone marrow and by the extent of morphologic dysplasia both of which have been shown to have 202 Am J Clin Pathol 2007;127: Downloaded 202 from

7 Hematopathology / ORIGINAL ARTICLE A B t-mds (n = 86) t-aml (n = 69) t-mds (n = 86) t-aml (n = 58) Balanced translocations (n = 11) Figure 3 Overall survival of patients with therapy-related myelodysplastic syndrome (t-mds) and therapy-related acute myeloid leukemia (t-aml), including (A) and separating out (B) patients with balanced translocations. The median survival differed by only 2 months between patients with t-mds (median survival time, 8.5 months) and patients with t-aml (median survival time, 6.5 months) (A, P =.043, Wilcoxon test). This borderline difference was still significant (P =.012, log-rank test; P =.038, Wilcoxon test) when patients with balanced translocations were excluded from the t-aml group (B). independent prognostic significance in de novo MDS 10,27,28 we questioned whether these parameters had prognostic significance in t-mds. When cases were analyzed according to the percentage of bone marrow blasts, there was no difference in outcome between cases with 5% or more blasts and those with fewer than 5%. Furthermore, patients with t-mds that we classified as RA, ie, fewer than 5% marrow blasts and only dyserythropoiesis, did not fare any better than patients with multilineage dysplasia classified as RCMD or patients with more blasts classified as RAEB. Although there were only 6 patients in the RA group, their median survival time was only 7.9 months, with 5 of 6 patients dead within 24 months of diagnosis. Our study indicates that there is a significantly worse outcome for patients with t-mds than for patients with de novo MDS classified into the same WHO category. For example, the median OS for our largest group of patients, t-rcmd, was only 8.5 months, which is considerably less than the 33 months reported by Germing et al 4 and the 49 months by Malcovati et al 6 for patients with de novo RCMD. The median survival time for therapy-related RA, 7.9 months, is much worse than the reported median survival times for de novo RA classified by WHO criteria, which range from 69 to 108 months. 4-6 Our observations are more in keeping with those made by Michels et al, 19 who documented a median survival of 4 months in their group of therapy-related RAEB cases classified according to the FAB criteria and no difference in outcome in terms of evolution to AML in t-mds cases with fewer than 5% vs 5% to 20% blasts. The second goal of this study was to determine whether cytogenetic abnormalities could be used to assign t-mds cases into various risk groups. Numerous articles have documented that most patients with t-mds have poor-risk cytogenetic abnormalities, but the role that karyotypic abnormalities might have in stratification of t-mds into various risk groups has not been fully addressed. In fact, t-mds cases were specifically excluded from the International Workshop on Prognostic Factors in MDS when the IPSS system was defined. 10 The majority of our t-mds cases (88%) had 1 or more cytogenetic abnormalities, comparable to that observed in other series of t-aml/mds and more than the reported frequency for de novo MDS (~50%). 31 Overall, abnormalities of chromosome 5 and/or 7 were most commonly observed, and almost half of the cases had complex karyotypes, consistent with previous reports The distribution of the cytogenetic abnormalities (chromosome 5 and/or 7, other abnormalities, and normal karyotype) was similar among the WHO subgroups of t-mds and between t-mds and t-aml. Most cases (70%) had poor-risk cytogenetic abnormalities according to the criteria of IPSS cytogenetic stratification. A statistically significant difference in survival time was observed among patients in good-, intermediate-, and poor-risk IPSS cytogenetic categories. In addition, patients with complex karyotypes ( 3 abnormalities) had a significantly shorter survival time than patients with fewer than 3 cytogenetic abnormalities. Am J Clin Pathol 2007;127:

8 Singh et al / T-MDS SUBCLASSIFICATION These results are relevant in view of results from recent large clinical trials, which suggest that as in de novo AML, the cytogenetic pattern is also an important prognostic factor in t- AML Schoch et al 34 demonstrated karyotype as an independent prognostic parameter for t-aml. In their study, patients in the favorable karyotype group, ie, t(8;21), inv(16), and t(15;17), had a rate of complete remission comparable to that of patients with de novo AML with similar karyotypic abnormalities, but this was not true for the intermediate and unfavorable groups of t-aml. Our study indicates that the IPSS cytogenetic stratification system is clinically relevant in t-mds as well. Because many of the patients in the poor-risk IPSS category had complex karyotypes and the majority of patients with complex karyotypes had abnormalities of chromosome 5 and/or 7, it may be reasonable to infer that the presence of abnormalities of chromosome 5 and/or 7 is the major determining factor for the poor outcome in t-mds overall and that additional abnormalities further contribute to the unfavorable prognosis. There was only a borderline difference in survival between cases initially diagnosed as t-mds or t-aml (Figure 3A, median, 8.5 vs 6.5 months, respectively). Although statistically significant, the median survival times for both are dismal. The distribution of cytogenetic abnormalities in t-mds and t-aml cases was similar except that the recurring balanced translocations were, by definition, included only in the latter group. In view of a better outcome reported in t-aml cases with recurring balanced translocations, 34 we reanalyzed the t-aml cases after exclusion of this group. In the resulting analysis (Figure 3B), there was a borderline improved longterm survival in t-mds cases compared with t-aml cases. However, there was no clinically significant difference at 6 months (t-mds, 62%; t-aml, 52%) or at 24 months (t-mds, 35%; t-aml, 26%). Furthermore, the median time to transformation from t-mds to t-aml was only 5.3 months. These data suggest that t-mds and t-aml without the recurring balanced chromosomal translocations are biologically similar, and it is reasonable to consider them together as a single syndrome (t-aml/mds), as recommended by the WHO. Poor survival of patients with t-aml/mds is a function of multiple competing risk factors, including the persistence of primary malignant disease, significant organ dysfunction from previous therapies, prolonged immunocompromised status, and lack of uniformly effective treatment. The presence of persistent primary disease in the bone marrow at the time of diagnosis of t-mds did not, however, correlate with poorer outcome in our study, but we did not evaluate the impact of persistent extramedullary disease. Patchy distribution of the residual primary disease and the influence of other comorbid conditions could make this finding more problematic. Treatment regimens for most cases of t-aml/mds have not been very successful. At present, donor hematopoietic stem cell transplantation offers the greatest potential for cure, particularly for younger patients and when patients undergo transplantation earlier in the disease course. 23,35,36 Risk stratification provides a framework to plan therapy and assess response. The results of our study indicate that morphologic subclassification of t-mds is not clinically useful for risk stratification and that t-mds as a group has an ominous outcome, similar to that of t-aml. Therefore, although the bone marrow blast counts are important for assessing response to treatment and should be performed, further classification of t- MDS using the same criteria as used for de novo MDS may not be necessary and, in fact, may provide misleading information for planning therapy, particularly for patients with low blast counts. Nevertheless, the number of patients in some subgroups in our study (eg, RA and MDS-U) is somewhat small, so that additional studies are needed to confirm our data. On the other hand, our results demonstrate that cytogenetic stratification based on the IPSS system or the complexity of cytogenetic abnormalities defines prognostic groups in t- MDS and is clinically relevant. From the 1 Section of Hematopathology, Department of Pathology, 2 Section of Hematology/Oncology, Department of Medicine, 3 Department of Health Studies, and the 4 Cancer Research Center, University of Chicago, Chicago, IL. Supported in part by grants CA14906, CALGB, and CA40046 from the National Cancer Institute, Bethesda, MD (M.M.L. and R.A.L.). 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