Prognostic factors in infants with acute myeloid leukemia - Nature

Leukemia (2000) 14, 684–687  2000 Macmillan Publishers Ltd All rights reserved 0887-6924/00 $15.00 www.nature.com/leu

Prognostic factors in infants with acute myeloid leukemia C-H Pui,1,2,3 SC Raimondi2, DK Srivastava4, X Tong4, FG Behm2, B Razzouk1, JE Rubnitz1, JT Sandlund1, WE Evans5,6 and R Ribeiro1 Departments of 1Hematology-Oncology, 2Pathology, 4Biostatistics and Epidemiology, and 5Pharmaceutical Sciences, St Jude Children’s Research Hospital; and University of Tennessee, 3College of Medicine and 6Pharmacy, Memphis, TN, USA

Little is known about the factors that affect treatment outcome in very young children with acute myeloid leukemia (AML). We therefore analyzed the prognostic impact of various presenting clinical and laboratory features by discrete age group in 299 children with AML treated in four consecutive clinical trials between 1980 and 1997. Differences in presenting features, as well as treatment outcome, were compared between children aged 12 months or less (n = 28) or 13 to 24 months (n = 28) and those more than 24 months of age (n = 243). Children in the two youngest groups (24 months of age or less) had similar presenting features and treatment outcome. Collectively, these 56 children were significantly more likely than the 243 older patients to have M4 or M5 leukemia (70% vs 30%), CNS leukemia (33% vs 22%), the t(9;11) (p22;q23) (18% vs 6%) or other 11q23 translocations (23% vs 3%), and less likely to have Auer rods (2% vs 54%) or the t(8;21) (q22;q22) (0% vs 17%). Among patients aged 24 months or less, two factors independently predicted a favorable prognosis: FAB M4 or M5 leukemia (relative risk of relapse, 0.4; 95% confidence interval, 0.2–0.9) and the t(9;11) (relative risk, 0.3; 95% confidence interval , 0.1–1.0). Leukocyte count and 11q23 translocations other than the t(9;11) lacked prognostic significance. Among older patients, a leukocyte count ⬍50 × 109/l and the presence of the t(9;11) conferred a favorable prognosis. Leukemia (2000) 14, 684–687. Keywords: karyotyping; t(9;11); infant leukemia; infant AML

Introduction Prognostic factors in infants with acute lymphoblastic leukemia (ALL) are well defined. Adverse factors include hyperleukocytosis, very young age (eg ⬍3 or ⬍6 months), the presence of central nervous system leukemia, the lack of CD10 expression on leukemic cells, MLL/11q23 rearrangements and a poor initial response to prednisone.1–13 In multivariate analyses, only MLL/11q23 rearrangement2,5–9,11 and poor prednisone response13 emerged with independent predictive strength. Recent studies suggest that the adverse prognosis of MLL/11q23 rearrangement is limited to cases with the t(4;11) (q21;q23),13–15 although we have found that cases of infant ALL with the t(11;19) (q23;p13.3) also have a poor prognosis.16 The factors that influence outcome in infants with acute myeloid leukemia (AML) remain generally obscure, for several reasons. First, there is no consistency among age cutpoints in reported series. Many studies combined infants less than 12 months of age with those 1–2 years old in a single group.17–22 Second, the prognosis of AML in very young patients as compared to older patients varied among different clinical protocols, underscoring the overriding importance of treatment efficacy. Some studies have shown an unfavorable outcome in very young patients,18,22 others have found comparable survival rates between the two age groups,17,21,23–26 while still others indicated a better prognosis for infants.19 Third, there Correspondence: C-H Pui, St Jude Children’s Research Hospital, 332 North Lauderdale, Memphis, TN 38105, USA; Fax: (901)521-9005 Received 2 December 1999; accepted 10 December 1999

are very few data on the blast cell genetics of infants with AML. Only four studies have attempted to assess the prognostic significance of MLL/11q23 rearrangements, the most common genetic lesion in infants with AML.9,27–29 In each, the findings were questionable due to the small number of patients, short follow-up duration or failure to distinguish between various subtypes of MLL/11q23 rearrangements. Here, we report on the prognostic factors in 56 very young children with AML, 28 ⭐ 12 months of age at diagnosis and 28 13–24 months of age, and contrast the findings with those in older children with this disease. Materials and methods From 1980 to 1997, 299 patients with newly diagnosed AML were enrolled in four successive clinical trials at this center (AML-80, AML-83, AML-87 and AML-91).30–32 Diagnoses were based on standard morphologic, cytochemical and immunophenotypic studies of leukemic cells. The protocols were approved by the institutional review board, and informed consent was obtained from patients, parents, or guardians, as appropriate. Metaphases of leukemic cells from bone marrow samples were prepared by a direct method, and a modified trypsin– Wright technique was used for G-banding. Chromosomes were described according to conventions of the International System for Human Cytogenetic Nomenclature (ISCN 1995).33

Statistical analysis Differences in the distribution of clinical and biologic features between subgroups of patients were analyzed by the twotailed Fisher’s exact test. Life-table estimates of event-free survival were derived by the method of Kaplan and Meier, and compared with the long-rank test. Event-free survival was measured from the date of protocol entry to the first failure of any kind (relapse, second malignancy or death) or to the date of the last follow-up examination. Patients who did not achieve a complete remission were assigned an event-free survival time of zero. The Cox proportional-hazards model was used to analyze the influence of potential prognostic factors on event-free survival. All variables significant at the 0.10 level were entered into the multivariate model; the variables were removed if they did not contribute significantly to the model based on the likelihood ratio test. Relative risks with 95% confidence intervals were calculated. Results Of 299 patients with AML, 28 (9.4%) were ⭐12 months at diagnosis, 28 (9.4%) were 13–24 months of age, and 243 (81.3%) were ⬎24 months old. There were no significant

Infant acute myeloid leukemia C-H Pui et al

differences in the presenting clinical or laboratory features between the first two age groups, except for a slightly higher frequency of the FAB M4 or M5 subtype of AML among children ⭐12 months of age (P = 0.08; Table 1). By comparison with patients ⬎24 months old, the ⭐12 month and the 13– 24 month age groups were both more likely to have M4 or M5 leukemia, the t(9;11) (p22;q23) or other 11q23 translocations, and less likely to have Auer rods or the t(8;21) (q22;q22). Because event-free survival did not differ significantly among the four clinical trials (P = 0.58, data not shown), they were combined for subsequent analyses. Eventfree survival estimates also did not differ significantly among the three age groups: the 5-year rates (±s.e.) were 32% ± 0. 1% for the youngest group, 34% ± 0.1% for the intermediate age group, and 27% ± 3% for the oldest group. Because children in the two younger groups had similar presenting features and treatment outcome, they were combined for the analysis of prognostic factors. Among these 56 children, M4 or M5 leukemia, the presence of the t(9;11) and female gender were associated with a favorable prognosis in univariate analysis (Table 2). A Cox proportional-hazards model identified M4 or M5 leukemia (relative risk of relapse, 0.4; 95% confidence interval, 0.2–0.9) and the presence of the t(9;11) (relative risk, 0.3; 95% confidence interval, 0.1– 1.0) as independent prognostic factors. The outcome of patients with 11q23 rearrangements other than the t(9;11) did not differ significantly from that of other patients (5-year eventfree survival, 23% ± 14% vs 25% ± 7%). Among patients ⬎24 months of age, a low leukocyte count (⬍50 × 109/l) and the presence of the t(9;11) conferred a favorable prognosis (data not shown). Likewise, 11q23 rearrangements other than the t(9;11) lacked prognostic impact in this older age group.

Table 1

Table 2 Adverse prognostic factors in children ⭐24 months of age at diagnosis of AMLa

Variable

5-year eventfree survival (% ± s.e.)

FAB type Others (n = 17) M4 or M5 (n = 39) Cytogenetics Others (n = 46) t(9;11) (p22;q23) (n = 10) Gender Male (n = 27) Female (n = 29)

685

Relative risk (95% CI)

7±5 44 ± 9 P ⬍ 0.001b

0.4 (0.2–0.9) P = 0.03c

25 ± 7 70 ± 16 P = 0.01b

0.3 (0.1–1.0) P = 0.06c

16 ± 7 48 ± 10 P = 0.02b

0.6 (0.3–1.2) P = 0.20c

CI, confidence interval; s.e., standard error. a Variables without prognostic significance include leukocyte count, liver size and CNS leukemia. b From the log-rank test. c From the Cox proportional-hazard model.

Discussion We demonstrate that the M4 and M5 subtypes of AML, the presence of the t(9;11) and female gender are all associated with a favorable prognosis in very young children with AML. In the study of Grier et al,18 the M4 and M5 subtypes and age ⬍2 years were adverse prognostic features, and the poor prognosis of patients ⬍2 years old was largely due to the pre-

Comparison of presenting features among AML patients of different agesa

Feature

⭐12 months (n = 28) No. P

Leukocyte count (×109/l) ⬍50 ⭓50

14 14

CNS leukemia Absent Present

14 10

FAB subtype M4 or M5 Others

23 5

Auer rods Yes No

0 28

Cytogenetics findings t(9;11) (p22;q23) Other 11q23 t(8;21) (q22;q22) t(15;17) (q22;q12-21) inv (16) +21 Normal Miscellaneous

5 7 0 0 1 0 4 10

13–24 months (n = 28) No. P

0.03

NS 21 7

0.04

173 70 0.81

21 7 ⬍0.001

184 53 0.01

16 12 ⬍0.001

72 171 ⬍0.001

1 27 0.02 ⬍0.001 0.02 NS NS NS NS NS

⬎24 months (n = 243) No.

5 6 0 0 2 0 2 10

130 110 0.02 0.001 0.02 NS NS NS NS NS

13 8 39 14 16 1 50 65

a P values refer to comparisons between the ⭐12 month or 13–24 months age group with ⬎24 month group. NS, not significant. Data sets incomplete for some patients.

Leukemia


686

ponderance of M5 leukemia in this age group. This difference in the prognostic impact of M4 and M5 subtypes could be due to the use of different treatment regimens. Our treatment protocols included the epipodophyllotoxins, which are highly effective against M5 leukemia in infants34,35 and in recent years they also incorporated 2-chlorodeoxyadenosine, an agent which appears particularly effective against M5 AML (RC Ribeiro, unpublished observation). While male gender is a recognized adverse feature in childhood ALL,36,37 it generally lacks prognostic significance in studies of AML. However, Lie et al25 found male gender to be the strongest predictor of a poor outcome among patients treated in two consecutive trials for childhood AML. We also found that boys fared worse than girls, although the comparison did not attain statistical significance in multivariate analysis. There were no significant differences between boys and girls in the frequency of M4 and M5 leukemia or the t(9;11) (data not shown). Hence, the basis for the poor outcome of males observed in our study and that of Lie et al25 is unclear, especially in view of the lack of similarities between treatment regimens. There have been four studies of MLL/11q23 rearrangements in infant AML.9,27–29 These abnormalities were found in approximately 50% to 60% of cases in each of the four studies and were associated with an M4 or M5 subtype and hyperleukocytosis. MLL/11q23 rearrangements lacked prognostic significance in three studies,9,27,29 but were associated with a trend towards a worse outcome in the fourth.28 None of the studies analyzed treatment outcome according to specific MLL/11q23 rearrangements. In the present study, we demonstrate for the first time that the t(9;11) confers a favorable outcome, whereas other MLL/11q23 rearrangements lack prognostic significance among very young children with AML. The t(9;11) was also associated with a favorable prognosis in older children with AML, a finding that confirms previous reports.38–40 Similarly, MLL/11q23 rearrangements in childhood ALL denote heterogeneous diseases with varying prognoses ranging from very favorable to dismal.41 The prognostic significance of other genetic abnormalities could not be assessed in this study because of the small number of cases in each subgroup. The t(8;21) and t(15;17), two of the most common translocations in older children with AML, were conspicuously absent in the very young age group. In fact, these two translocations apparently have not been reported in infant AML, suggesting different mechanisms of leukemogenesis, including different target cells, in very young children with this disease. Acknowledgements We thank Annette C Stone for data management and Doris Hurdle for typing the manuscript. This work was supported by grant Nos CA21765 and CA20180 from the National Cancer Institute, by a Center of Excellence grant from the State of Tennessee, and by the American Lebanese Syrian Associated Charities (ALSAC). References 1 Pui C-H, Frankel LS, Carroll AJ, Raimondi SC, Shuster JJ, Head DR, Crist WM, Land VJ, Pullen DJ, Steuber CP, Behm FG, Borowitz MJ. Clinical characteristics and treatment outcome of childhood acute lymphoblastic leukemia with the t(4;11) (q21;q23): a collaborative study of 40 cases. Blood 1991; 77: 440–447.

Leukemia

2 Chen C-S, Sorensen PHB, Domer PH, Reaman GH, Korsmeyer SJ, Heerema NA, Hammond GD, Kersey JH. Molecular rearrangements on chromosome 11q23 predominate in infant acute lymphoblastic leukemia and are associated with specific biologic variables and poor outcome. Blood 1993; 81: 2386–2393. 3 Basso G, Giuseppe B, Rondelli R, Covezzoli A, Putti MC. The role of immunophenotype in acute lymphoblastic leukemia of infant age. Leuk Lymphoma 1994; 15: 51–60. 4 Chessells JM, Eden OB, Bailey CC, Lilleyman JS, Richards SM. Acute lymphoblastic leukaemia in infancy: experience MRC UKALL Trials. Report from the Medical Research Council Working Party on Childhood Leukaemia. Leukemia 1994; 8: 1275–1279. 5 Pui C-H, Behm FG, Downing JR, Hancock ML, Shurtleff SA, Ribeiro RC, Head DR, Mahmoud HH, Sandlund JT, Furman WL, Roberts WM, Crist WM, Raimondi SC. 11q23/MLL rearrangement confers a poor prognosis in infants with acute lymphoblastic leukemia. J Clin Oncol 1994; 12: 909–915. 6 Rubnitz JE, Link MP, Shuster JJ, Carroll AJ, Hakami N, Frankel LS, Pullen DJ, Cleary ML. Frequency and prognostic significance of HRX rearrangements in infant acute lymphoblasitc leukemia: A Pediatric Oncology Group Study. Blood 1994; 84: 570–573. 7 Cimino G, Rapanotti MC, Rivolta A, Lo Coco F, D’Arcangelo E, Rondelli R, Basso G, Barisone E, Rosanda C, Santostasi T, Canaani E, Masera G, Mandelli F, Biondi A. Prognostic relevance of ALL1 gene rearrangement in infant acute leukemias. Leukemia 1995; 9: 391–395. 8 Pui C-H, Kane JR, Crist WM. Biology and treatment of infant leukemias. Leukemia 1995; 9: 762–769. 9 Pui C-H, Ribeiro RC, Campana D, Raimondi SC, Hancock ML, Behm FG, Sandlund JT, Rivera GK, Evans WE, Crist WM, Krance R. Prognostic factors in the acute lymphoid and myeloid leukemias of infants. Leukemia 1995; 10: 952–956. 10 Silverman LB, McLean TW, Gelber RD, Donnelly MJ, Gilliland DG, Tarbell NJ, Sallan SE. Intensified therapy for infants with acute lymphoblastic leukemia. Results from the Dana-Farber Cancer Institute Consortium. Cancer 1997; 80: 2285–2295. 11 Taki T, Ida K, Bessho F, Hanada R, Kikuchi K, Yamamoto K, Sako M, Tsuchida M, Seto M, Ueda R, Hayashi Y. Frequency and clinical significance of the MLL gene rearrangements in infant acute leukemia. Leukemia 1996; 10: 1303–1307. 12 Reaman GH, Sposto R, Sensel MG, Lange BJ, Feusner JH, Heerema NA, Leonard M, Holmes EJ, Sather HN, Pendergrass TW, Johnstone HS, O’Brien RT, Steinherz PG, Zeltzer PM, Gaynon, PS, Trigg ME, Uckun FM. Treatment outcome and prognostic factors for infants with acute lymphoblastic leukemia treated on two consecutive trials of the Children’s Cancer Group. J Clin Oncol 1999; 17: 445–455. 13 Do¨rdelmann M, Reiter A, Borkhardt A, Ludwig W-D, Go¨tz N, Viehmann S, Gadner H, Riehm J, Schrappe M. Prednisone response is the strongest predictor of treatment outcome in infant acute lymphoblastic leukemia. Blood 1999; 94: 1209–1217. 14 Heerema NA, Arthur DC, Sather H, Albo V, Feusner J, Lange BJ, Steinherz PG, Zeltzer P, Hammond D, Reaman GH. Cytogenetic features of infants less than 12 months of age at diagnosis of acute lymphoblastic leukemia: impact of the 11q23 breakpoint on outcome: a report of the Children’s Cancer Group. Blood 1994; 83: 2274–2284. 15 Heerema NA, Sather HN, Ge J, Arthur DC, Hilden JM, Trigg ME, Reaman GH. Cytogenetic studies of infant acute lymphoblastic leukemia: poor prognosis of infants with t(4;11) – a report of the Children’s Cancer Group. Leukemia 1999; 13: 679–686. 16 Rubnitz JE, Camitta BM, Mahmoud H, Raimondi SC, Carroll AJ, Borowitz MJ, Shuster JJ, Link MP, Pullen DJ, Downing JR, Behm FG, Pui, C-H. Childhood acute lymphoblastic leukemia with the MLL-ENL fusion and t(11;19) (q23;p13.3) translocation. J Clin Oncol 1999; 17: 191–196. 17 Amadori S, Ceci A, Comelli Adriana C, Comelli A, Madon E, Masera G, Nespoli L, Paolucci G, Zanesco L, Covelli A, Mandelli F. Treatment of acute myelogenous leukemia in children: results of the Italian Cooperative Study AIEOP/LAM 8204. J Clin Oncol 1987; 5: 1356–1363. 18 Grier HE, Gelber RD, Camitta BM, Delorey MJ, Link MP, Price KN, Leavitt PR, Weinstein HJ. Prognostic factors in childhood acute myelogenous leukemia. J Clin Oncol 1987; 5: 1026–1032. 19 Ravindranath Y, Steuber CP, Krischer J, Civin CI, Ducore J, Vega


20

21

22 23 24

25

26

27

28

29

R, Pitel P, Inoue S, Bleher E, Sexauer C, Hutter J, Vietti T. Highdose cytarabine for intensification of early therapy of childhood acute myeloid leukemia: a Pediatric Oncology Group study. J Clin Oncol 1991; 9: 572–580. Ravindranath Y, Yeager AM, Chang MN, Steuber CP, Krischer J, Graham-Pole J, Carroll A, Inoue S, Camitta B, Weinstein HJ. Autologous bone marrow transplantation versus intensive consolidation chemotherapy for acute myeloid leukemia in childhood. New Engl J Med 1996; 334: 1428–1434. Woods WG, Kobrinsky N, Buckley JD, Lee JW, Sanders J, Neudorf S, Gold S, Barnard DR, DeSwarte J, Dusenbery K, Kalousek D, Arthur DC, Lange BJ. Timed-sequential induction therapy improves postremission outcome in acute myeloid leukemia: a report from the Children’s Cancer Group. Blood 1996; 87: 4979–4989. Creutzig U, Zimmermann M, Ritter J, Henze G, Graf N, Lo¨ffler H, Schellong G. Definition of a standard-risk group in children with AML. Br J Haematol 1999; 104: 630–639. Pui C-H, Kalwinsky DK, Schell MJ, Mason CA, Mirro J Jr, Dahl GV. Acute nonlymphoblastic leukemia in infants: clinical presentation and outcome. J Clin Oncol 1988; 6: 1008–1013. Buckley JD, Chard RL, Baehner RL, Nesbit ME, Lampkin BC, Woods WG, Hammond GD. Improvement in outcome for children with acute nonlymphocytic leukemia. A report from the Childrens Cancer Study Group. Cancer 1989; 63: 1457–1465. Lie SO, Jonmundsson G, Mellander L, Siimes MA, Yssing M, Gustafsson G. A population-based study of 272 children with acute myeloid leukaemia treated on two consecutive protocols with different intensity: best outcome in girls, infants, and children with Down’s syndrome. Br J Haematol 1996; 94: 82–88. Stevens RF, Hann IM, Wheatley K, Gray RG. Marked improvements in outcome with chemotherapy alone in paediatric acute myeloid leukaemia: results of the United Kingdom Medical research Council’s 10th AML trial. Br J Haematol 1998; 101: 130–140. Sorensen PHB, Chen C-S, Smith FO, Arthur DC, Domer PH, Bernstein ID, Korsmeyer SJ, Hammond GD, Kersey JH. Molecular rearrangements of the MLL gene are present in most cases of infant acute myeloid leukemia and are strongly correlated with monocytic or myelomonocytic phenotypes. J Clin Invest 1994; 93: 429–437. Hilden JM, Smith FO, Frestedt JL, McGlennen R, Howells WB, Sorensen PHB, Arthur DC, Woods WG, Buckley J, Bernstein ID, Kersey JH. MLL gene rearangement, cytogenetic 11q23 abnormalities, and expression of the NG2 molecule in infant acute myeloid leukemia. Blood 1997; 89: 3801–3805. Satake N, Maseki N, Nishiyama M, Kobayashi H, Sakurai M, Inaba H, Katano N, Horikoshi Y, Eguchi H, Miyake M, Seto M, Kaneko Y. Chromosome abnormalities and MLL rearrangements in acute myeloid leukemia of infants. Leukemia 1999; 13: 1013–1017.

30 Dahl GV, Kalwinsky DK, Mirro J Jr, Look AT, Pui C-H, Murphy SB, Mason C, Ruggiero M, Schell M, Johnson FL, Thomas ED. Allogeneic bone marrow transplantation in a program of intensive sequential chemotherapy for children and young adults with acute nonlymphocytic leukemia in first remission. J Clin Oncol 1990; 8: 295–303. 31 Kalwinsky D,Mirro J Jr, Schell M, Behm F, Mason C, Dahl GV. Early intensification of chemotherapy for childhood acute nonlymphoblastic leukemia: improved remission induction with a fivedrug regimen including etoposide. J Clin Oncol 1988; 6: 1134– 1143. 32 Hurwitz CA, Krance R, Schell MJ, Santana VM, Brenner MK, Ribeiro R, Roberts WM, Mahmoud H, Belt J, Crom W, Shearer PD, Mirro J Jr. Current strategies for treatment of acute myeloid leukemia at St. Jude Children’s Research Hospital. Leukemia 1992; 6 (Suppl. 2): 39–43. 33 ISCN 1995. Mitelman F (ed). An International System for Human Cytogenetic Nomenclature. Karger: Basel, 1995. 34 Odom LF, Gordon EM. Acute monoblastic leukemia in infancy and early childhood: successful treatment with an epipodophyllotoxin. Blood 1984; 64: 875–882. 35 Nishikawa A, Nakamura Y, Nobori U, Aoki T, Higashino H, Matsui T, Kobayashi Y, Yamashita M, Unishi G. Acute monocytic leukemia in children. Response to VP-16–213 as a single agent. Cancer 1987; 60: 2146–2149. 36 Shuster JJ, Wacker SP, Pullen J, Humbert J, Land VJ Jr, Mahoney DH, Lauer S, Look AT, Borowitz MJ, Carroll AJ, Camitta B. Prognostic significance of sex in childhood B-precursor acute lymphoblastic leukemia: a Pediatric Oncology Group Study. J Clin Oncol 1998; 16: 2854–2863. 37 Pui C-H, Boyett JM, Relling MV, Harrison PL, Rivera GK, Behm FG, Sandlund JT, Ribeiro RC, Rubnitz JE, Gajjar A, Evans WE. Sex differences in prognosis for children with acute lymphoblastic leukemia. J Clin Oncol 1999; 17: 818–824. 38 Kalwinsky DK, Raimondi SC, Schell MJ, Mirro J Jr, Santana VM, Behm F, Dahl GV, Williams D. Prognostic importance of cytogenetic subgroups in de novo pediatric acute nonlymphocytic leukemia. J Clin Oncol 1990; 8: 78–83. 39 Martinez-Climent JA, Lane NJ, Rubin CM, Morgan E, Johnstone HS, Mick R, Murphy SB, Vardiman JW, Larson RA, Le Beau MM, Rowley JD. Clinical and prognostic significance of chromosomal abnormalities in childhood acute myeloid leukemia de novo. Leukemia 1995; 9: 95–101. 40 Mro´zek K, Heinonen K, Lawrence D, Carroll AJ, Koduru PRK, Rao KW, Strout MP, Hutchison RE, Moore JO, Mayer RJ, Schiffer CA, Bloomfield CD. Adult patients with de novo acute myeloid leukemia and t(9;11) (p22;q23) have a superior outcome to patients with other translocations involving band 11q23: A Cancer and Leukemia Group B Study. Blood 1997; 90: 4532–4538. 41 Pui C-H, Evans WE. Acute lymphoblastic leukemia. New Engl J Med 1998; 339: 605–615.

687

Leukemia