Leukemia (2005) 19, 2101–2116 & 2005 Nature Publishing Group All rights reserved 0887-6924/05 $30.00 www.nature.com/leu Pediatric Oncology Group (POG) studies of acute myeloid leukemia (AML): a review of four consecutive childhood AML trials conducted between 1981 and 2000

Y Ravindranath1, M Chang2, CP Steuber3, D Becton4, G Dahl5, C Civin6, B Camitta7, A Carroll8, SC Raimondi9 and HJ Weinstein10, for the Pediatric Oncology Group

1Department of Pediatrics, Children’s Hospital of Michigan and Wayne State University, Detroit, MI, USA; 2Department of Statistics, University of Florida, Gainesville, FL, USA; 3Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA; 4Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR, USA; 5Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA; 6Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA; 7Department of Pediatrics, Midwest Children’s Hospital and Medical College of Wisconsin, Milwaukee, WI, USA; 8Department of Genetics, University of Alabama, Birmingham, AL, USA; 9Department of Pathology, St Jude Children’s Hospital, Memphis, TN, USA; and 10Division of Pediatric Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA

From 1981 to 2000, a total of 1823 children with acute myeloid Introduction leukemia (AML) enrolled on four consecutive Pediatric Oncology Group (POG) clinical trials. POG 8101 demonstrated that the The general focus of the Pediatric Oncology Group (POG) induction rate associated with the 3 þ 7 þ 7 combination of daunorubicin, Ara-C, and 6-thioguanine (DAT) was greater than acute myeloid leukemia (AML) studies was to explore the that associated with an induction regimen used to treat acute use of cytarabine dose intensification in the treatment for lymphoblastic leukemia (82 vs 61%; P ¼ 0.02). Designed as a childhood AML. In this paper, we review four successive POG pilot study to determine the feasibility of administration of AML studies in which a stepwise dose intensification of noncross-resistant drug pairs and later modified to assess the cytarabine was introduced along with anthracyclines. During effect of dose intensification of Ara-C during the second these studies, we also evaluated the role of autologous and induction course, POG 8498 confirmed the high initial rate of response to DAT (84.2%) and showed that dose intensification of allogeneic bone marrow transplantation (BMT) in first remission Ara-C during the second induction course resulted in a trend in the treatment of childhood AML. Further centralized, toward higher event-free survival (EFS) estimates than did morphology review immunophenotyping and cytogenetic standard-dose DAT (2 þ 5) during the second induction course evaluation was incorporated in successive, thus allowing for (5 year EFS estimates, 22 vs 27%; P ¼ 0.33). Age o2 years and evaluation of prognostic features in large cohorts of childhood leukocyte count o100 000/mm3 emerged as significantly good prognostic factors. The most significant observation made in the AML cases. POG 8498 study was the markedly superior outcome of children Since 1981, four consecutive AML trials have been perfor- with Down’s syndrome who were treated on the high-dose Ara-C med by the POG. Table 1 gives an overview of the number regimen. POG 8821 compared the efficacy of autologous bone of centers involved in three of the four trials, the average marrow transplantation (BMT) with that of intensive consolida- numbers of patients, and the distribution of patients by age at tion chemotherapy. Intent-to-treat analysis revealed similar 5- diagnosis. year EFS estimates for the group that underwent autologous BMT (3674.7%) and for the group that received only intensive Before 1981, patients with AML were treated with regimens chemotherapy (3574.5%) (P ¼ 0.25). There was a high rate of similar to those used to treat childhood acute lymphoblastic treatment-related mortality in the autologous transplantation leukemia (ALL), and the results of the AML treatment were group. The study demonstrated superior results of allogeneic relatively poor. Clinical trials of more intensive regimens BMT for patients with histocompatible related donors (5-year consisting of cytarabine (Ara-C) and anthracycline started with 7 EFS estimate 63 5.4%) and of children with Down’s syndrome the POG 8101 study.1–3 In POG 8101 patients were randomly (5-year EFS estimate, 6678.6%). The POG 9421 AML study þ þ evaluated high-dose Ara-C as part of the first induction course assigned to receive either the 3 7 7 regimen of DAT and the use of the multidrug resistance modulator cyclosporine. (daunorubicin, Ara-C, and 6-thioguinine) or a regimen that Preliminary results showed that patients receiving both high- had been used to treat ALL and included vincristine, dexa- dose Ara-C for remission induction and the MDR modulator for methasone, and Ara-C. The therapy given after remission consolidation had a superior outcome (5-year EFS estimate, induction included a long maintenance phase given over 7 42 8.2%) than did patients receiving other treatment; however, 2 years. the difference was not statistically significant. These four studies demonstrate the importance of dose intensification of The POG 8498 pilot study evaluated the efficacy and toxicity Ara-C in the treatment of childhood AML; cytogenetics as the of high-dose Ara-C given both as a second induction course after single most prognostic factor and the unique curability of AML DAT and as consolidation therapy immediately after the in children with Down’s syndrome. completion of remission induction therapy. Multiagent che- Leukemia (2005) 19, 2101–2116. doi:10.1038/sj.leu.2403927; motherapy after remission induction was modeled after the published online 1 September 2005 VAPA regimen of Weinstein et al.4 The results clearly confirmed Keywords: AML; childhood; treatment; bone marrow the efficacy of the DAT regimen as part of initial induction transplantation; daunorubicin dosing; high-dose cytarabine therapy and established a toxicity profile for high-dose Ara-C in childhood AML.4 In addition, the immunophenotypic charac- Correspondence: Dr Y Ravindranath, Georgie Ginopolis Chair for teristics of childhood AML were analyzed in detail.5 Finally, the Pediatric Cancer and Hematology, Wayne State University School of superior outcome of children with Down’s syndrome treated on Medicine, Children’s Hospital of Michigan-2M34, 3901 Beaubien high-dose Ara-C-containing regimens was first recognized.6 Boulevard, Detroit, MI 48201, USA; Fax: þ 313 745 5237; E-mail: [email protected] POG 8821 compared the efficacy of autologous BMT during Received 8 February 2005; accepted 14 April 2005; published online early remission with that of intensive chemotherapy alone. 1 September 2005 Patients with matched family donors were eligible to proceed Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2102 Table 1 Accrual and follow-up of all patients

Trial Period of No. of patients/No. of eligible No. of participating Average no. of patients Average No. of patients accrual patients/No. of eligible patients centers without DS enrolled at each without DS enrolled except those with DS center (range) each year

8101 7/81–1/86 267/264/257 52 4.9 (1–21) 57 8498 7/84–7/88 294/288/274 56 4.9 (1–21) 68 8821 6/88–3/93 666/649/615 88 7.0 (1–22) 130

to allogeneic BMT.7 The outcome of patients who underwent a POG AML protocols- Treatment Schemas autologous BMT as given in this study was not superior to that of Ara-C/TG patients who received only intensive chemotherapy.7 8101-II DAT (3+7)* DAT (2+5) TG/Ara-C/AZ DA The POG 9421 study compared the results of treatment using standard-dose DAT as a first induction course with 8498- I DAT (3+7)* DAT (2+5) HdA+L-Asp (4courses) those of treatment using high-dose Ara-C (1 g/m2 per dose; total, 14 doses), daunorubicin (45 mg/m2 daily for 3 days), and 8498- II DAT (3+7)* HdA HdA X 1 course 6-thioguanine (for 7 days) given as a first induction course. The 6 6 safety and efficacy of an MDR modulator administered during

intensification therapy was also investigated. Preliminary results Vp/AZ*- 4 courses of this trial are presented in this paper. POMP*- 4 courses

Patients and methods Ara-C Daily x5- 4 courses D = Daunorubicin; A and Ara-C = cytarabine; T, TG = Thioguanine ; AZ = Azacytidine; POMP = Eligibility Mercaptopurine, Oncovin (vincristine), Methotrexate, Prednisolone

The main entry criteria of studies 8101, 8498, and 8821 were b Chemotherapy vs ABMT for Childhood AML: POG 8821 age p21 years and previously untreated AML (patients with Treatment Schema secondary AML were eligible if the treatment was for another DAT* type of malignancy); patients with an isolated chloroma were eligible. Patients with myelodysplastic syndrome were not HdA6 eligible, and starting with the POG 8498 study, data of patients Remission (M1 + M2a <15% blasts) with Down’s syndrome were analyzed separately from those of the other patient groups. Randomize For POG 9421, patients with APL were not eligible, and patients with Down’s syndrome were not eligible for random VP/AZ* VP/AZ* VP/AZ* assignment to the groups that received high-dose DAT or cyclosporine (CsA); instead, patients with Down’s syndrome Chemo ABMT AlloBMT were treated with the standard chemotherapy regimen.

Chemo = D+ HdA6 DAT VP/AZHdA6 DAT VP/AZ Diagnosis * = IT ara-c X 2 D = Daunorubicin; A = cytarabine; had = high dose cytarabine ; T = Thioguanine ; AZ = Standard French–American–British (FAB) criteria were used in Azacytidine; ABMT= autologous bone marrow transplantation: AlloBMT = allogeneic BMT. IT = the initial diagnosis of AML and its subtypes. Central pathology intrathecal review occurred in all studies. Diagnosis of M0 and M7 subtypes required confirmation by immunologic methods. The day-14 c POG 9421 Schema bone marrow aspirates were reviewed locally. Induction I Induction II Consolidation Std DAT Treatment VP/Mxa +CSA HdA x 10 doses The treatments are shown schematically in Figure 1. The drug DHdAT doses are summarized in Table 2. HdA x 10 doses Drug doses: D= 45mg/m2 x 3; A=100mg/m2-7d; T= (all patients) 100mg/m2-7d Figure 1 Treatment schema of three consecutive POG AML DHdAT: D and T same as above; A= 1mg/m2 q 12hr x 14 HdA: Ara-c 1mg/m2 q12hr x 10doses studies. (a) Treatment schema of the POG 8101 and 8498 studies. In *VP/Mxa VP 100mg/m2 x 5d; Mxa= 10mg/m2 x 5d POG 8101, patients assigned to group II Received the 3 þ 7 regimen of * Reduce dose of VP and Mxa by 40% if randomized to CSA DAT, whereas patients in group I received a regimen designed VP/Mxa +CSA originally to treat ALL (not shown???). In POG 8498, patients were assigned randomly to either group I (8498-I) or group II (8498-II). (b) Treatment schema of the POG 8821 study. (c) Treatment schema of Std DAT = Standard dose DAT (D = daunorubicin; A = Cytarabine; T = Thioguanine); SHdAT = the POG 9421 study. DAT with high dose cytarabine; VP = etopside, Mxa = Mitoxantrone; CSA = cyclosporine.

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2103 Table 2 Pediatric oncology group AML studies- 8101, 8498, 8821- chemotherapy schedules and drug doses

Protocol Treatment Comments Drug Doses (mg/m2)

Cytarabine Daunorubicin Etoposide

8101 Induction therapy: Treatment 1 (DAT): daunorubicin: 45 mg/m2/day, i.v. First introduction of AML 700 135 push, on days 1–3; cytarabine: 100 mg/m2/day, i.v. specific induction continuous infusion, on days 1–7; thioguanine: 100 mg/m2/day, single dose on days 1–7.

Treatment 2 (Vadx): vincristine: 2.0 mg/m2/week, i.v. 700 push, on days 1, 8, 15 (maximum dose 2.0 mg); cytarabine: 100 mg/m2/day, i.v. continuous infusion, on days 1–7; dexamethasone: 6.0 mg/m2/day, orally, in three divided doses for 21 days only.

Consolidation therapy for patients entering complete remission: Consolidation: thioguanine: 100 mg/m2, orally, on 200 days 1–4, as a single dose; cytarabine: 100 mg/m2/ day, i.v. continuous infusion on days 5–6; azacytidine: 100 mg/m2/day, i.v. continuous infusion, on days 7–8.

Continuation or maintenance therapy: Maintenance therapy over rerandomization of patients in remission: 2 years Arm 1: two-cycle therapy: Cycle 1:cytarabine: 100 mg/m2/i.v., or 400 subcutaneously, as a single dose on days 1–4; thioguanine: 100 mg/m2/day, orally, 12-h after cytarabine. Cycle 2: vincristine: 2.0 mg/m2, i.v. push, on day 1 (maximum dose: 2.0 mg); cytarabine: 35 mg/m2, i.v. push, every 8 h for 12 doses; cyclophosphamide: 35 mg/m2, i.v. push, every 8 h for 12 doses; prednisone: 60 mg/m2/day, orally, in three divided doses given every 8 h.

Arm II: four-cycle therapy: Cycle 1: daunorubicin: 90 mg/m2, i.v., on day 1; 500 cytarabine: 100 mg/m2/day, i.v. continuous infusion, for 5 days. Cycle 2: same as cycle 1 of arm I. 400 Cycle 3: same as consolidation therapy (above). 200 Cycle 4: same as the cycle 2 of Arm I. 420 90

Total dosages for Treatment 2/arm 2 3120 225

CNS therapy: IT therapy: a total of 6 dosage of triple IT chemo + XRT for CNS IT therapy were given, including those administered prophylaxis during induction, with adjusted dosages. After remission, the remainder of the six spinal taps were done twice weekly during the period of cranial radiation.

Cranial radiation: For age 42 years: 2400 cGy in 200 cGy fractions; For age 1–2 years: 2000 cGy in 150 cGy fractions; For age o1 year: 1500 cGy in 100 cGy fractions.

8498 GROUP I: Induction: Course I: daunorubicin 45 mg/m2/day, i.v., days 1–3; 700 135 Ara-C 100 mg/m2/day, i.v., days 1–7; thioguanine 100 mg/m2/day, orally, days 1–7. Course II: daunorubicin 45 mg/m2/day, i.v. bolus, 500 90 days 1–2; Ara-C 100 mg/m2/day, i.v., days 1–5; thioguanine 100 mg/m2/day, orally, days 1–5.

Postremission therapy: Cycle I (4 courses): high-dose cytarabine (Ara-C) 3 g/ High-dose Ara-C for 48 000 2 m , i.v., every 12 h  4 doses, days 1–2; L-Asp consolidation 10 000/m2, as single dose 6 h after last Ara-C dose.

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2104 Table 2 Continued

Protocol Treatment Comments Drug Doses (mg/m2)

Cytarabine Daunorubicin Etoposide

Cycle II (4 courses): VP (etoposide) 250 mg/m2, days Introduce etoposide 750 1–3; (Az) azacytidine 300 mg/m2, days 4, 5. in AML therapy Cycle III (4 courses): prednisone 800 mg/m2, i.v., Delete XRT as a part days 1–3; vincristine 1.5 mg/m2, i.v., (maximum dose of CNS prophylaxis 2.0 mg), day 1; methotrexate 7.5 mg/m2, days 1–5; mercaptopurine 500 mg/m2, days 1–5. Cycle IV (4 courses): Ara-C 200 mg/m2, i.v. by 4000 continuous infusion, days 1–5.

Total doses for group I patients 53 200 225 750

CNS prophylaxis: IT Ara-C 40 mg/m2, days 1 and 7 of course 1 of induction, day 1 of the first two courses of VP/Az, and first and second courses of POMP (total of 6 doses of IT Ara-C). CNS disease at diagnosis: IT Ara-C 40 mg/m2 Â 4 during inductions, days 1 and 7, and days 13 and 22. If CNS remission is achieved, remainder of the CNS therapy as above (total of eight doses of IT Ara-C).

GROUP II Induction: Course I: same as in group I. 700 135 Course II: High-dose cytarabine (HdA) 3 g/m2, every High-dose Ara-C for 18 000 12 h  6 doses, days 1–3. second induction course

Postremission therapy: Group II: Cycle I (1 course): high-dose cytarabine (Ara-C) 3 g/ 18 000 m2, i.v., every 12 h  6 doses, days 1–3. Cycle II (4 courses): same as in group I. Cycle III (4 courses): same as in group I. 750 Cycle IV (4 courses): same as in group I. 4000

Total doses for group II 40 700 135 750 CNS prophylaxis: same as in group I . CNS disease at diagnosis: same as in group I .

8821 Induction: Course I: daunorubicin 45 mg/m2, days 1–3; Randomized evaluation of 700 135 cytarabine 100 mg/m2/day, i.v. continuous infusion, intensive consolidation days 1–7; thioguanine 100 mg/m2/day, orally, days chemotherapy vs purged 1–7. autologous BMT early in remission. Cumulative dose intensification of Ara-C and Daunorubicin over previous POG studies Proceed to course II of induction (same as course I) either: on day 15 if bone marrow shows residual leukemia; otherwise, to begin when ANC X1000, and platelet count X100 000.

Course II: high-dose cytarabine (HdA) 3 g/m2, every 18 000 12 h  6 doses, days 1–3.

Randomization: Patient entering remission (having M1 marrow (o5% blasts) or M2a marrow [5–15% blasts) are eligible for randomization. Randomization includes either autologous bone marrow transplantation or intensive consolidation chemotherapy.

Consolidation: After randomization, all patients receive one course 750 of: etoposide 250 mg/m2/day, on days 1–3; azacytidine 300 mg/m2/day, on days 4 and 5; IT cytarabine 40 mg/m2, on days 1 and 7.

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2105 Table 2 Continued

Protocol Treatment Comments Drug Doses (mg/m2)

Cytarabine Daunorubicin Etoposide

Intensive consolidation therapy: Course I: daunorubicin 45 mg/m2, on day 1; high- 18 000 45 dose cytarabine (HdA) 3 g/m2, every 12 h  6 doses, days 1–3. Course II: daunorubicin 45 mg/m2, days 1–2; 500 90 cytarabine 100 mg/m2/d, i.v. continuous infusion, days 1–5; thioguanine 100 mg/m2/day, orally, days 1–5. Course III: etoposide 250 mg/m2/day, on days 1–3; 750 azacytidine 300 mg/m2/day, on days 4 and 5. Course IV: high-dose cytarabine (HdA) 3 g/m2, every 18 000 12 h  6 doses, days 1–3. Course V: daunorubicin 45 mg/m2, days 1–2; 500 90 cytarabine 100 mg/m2/day, i.v. continuous infusion, days 1–5; thioguanine 100 mg/m2/day, orally, days 1–5. Course VI: etoposide 250 mg/m2/day, on days 1–3; 750 azacytidine 300 mg/m2/day, on days 4 and 5.

Total drug doses for chemotherapy patients 55 700 360 2250

CNS therapy: IT cytarabine 40 mg/m2, on days 1 and 8 of first course of induction. Patients having CNS leukemia at the time of diagnosis are given additional doses given on days 12 and 19.

Local radiotherapy permitted for patients with CNS or extra-cranial mass lesions

Autologous bone marrow transplantation: Patients to undergo autologous BMT must have been in complete remission after consolidation course of etoposide and azacytidine, and be free of disseminated fungal disease.

Marrow harvesting: patient’s bone marrow is harvested 6–12 weeks after the start of etoposide and azacytidine. To eliminate myeloblasts, the harvested marrow is treated under sterile conditions for 30-min with perfosfamide (4-hydroperoxycyclo- phosphamide) at a concentration of 100 mg/ml, and an incubation hematocrit of 5–10%.

Preparative regimen: patients receive busulfan 4 mg/ m2/day, orally, every 6-h, on days 9, 8, 7, and 6 BEFORE transplantation; and, cyclophosphamide 50 mg/kg, i.v., days 5, 4, 3, and 2 BEFORE transplantation.

Infusion of marrow: after 1 day of REST, the cryopreserved marrow is thawed and infused, on day 0. All patients receive phenytoin, on days 11–4 BEFORE transplantation, as prophylaxis against seizures.

Remission Induction therapy: In the POG 8101, 8498, and In POG 9421 for remission induction patients who 8821 studies, the first course of remission induction therapy was were assigned randomly to standard DAT therapy (treatments the DAT regimen. The difference in induction therapy between 1, 2, and 5) in the POG 9421 trial received Ara-C (100 mg/m2 8498 and 8821 was the introduction of high-dose Ara-C as a per day) by continuous infusion for seven consecutive second induction course for Group II patients (see next days (total, 168 h); daunomycin (45 mg/m2 per day) by intra- paragraph) on 8498 and for all patients on POG 8821. In venous infusion over 15 min on days 1–3; and thioguanine POG 9421, the major change was the administration of high- (100 mg/m2 per day) orally for 7 days. Patients assigned dose Ara-C as part of the DAT regimen given as the first randomly to the HDAT group (treatments 3 and 4) received induction course to a particular group of patients. identical doses of daunomycin and thioguanine, but Ara-C

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2106 (1 g/m2 per dose) was administered as a 1-h infusion every 12 h etoposide and mitoxantrone at 60% of standard doses with for 7 consecutive days. CsA was expected to result in myelotoxicity similar to that observed when standard doses of the two are given without an MDR1-modulating agent. Post-induction therapy: In POG 8101 patients after remis- sion induction all patients received cranial radiation (age adjusted 1500–2400 cGy) and consolidation therapy with CNS therapy: Cranial radiation therapy was given to all thioguanine (Tg; days 1–4), Ara-C (days 5, 6) and azacytidine patients in POG 8101 but not to all patients in studies 8498, (Az; days 7, 8). Patients were then randomized to 2 years of 8821, and 9421. In these three latter studies, patients with maintenance therapy: arm 1–two cycle maintenance (cycle chloromas were permitted to receive radiation therapy, and low- 1 ¼ AraC/Tg; cycle 2 ¼ vincristine[Vcr]/Ara-C/cyclophospha- dose cranial irradiation was permitted for patients with CNS mide [Cy]/prednisone [pred]) or arm 2–four cycle maintenance leukostasis. In POG 8498, central nervous system (CNS) (DNR/Ara-C; Ara-C/Tg; Tg/Ara-C/Az and Vcr/Ara-C/Cy/Pred). prophylaxis consisted of Ara-C administered intrathecally on In the first phase of POG 8498,4 the second course of days 1 and 7 of course 1 of induction day 1 of the first two induction therapy was a 2 þ 5 þ 5 combination of DAT. Patients courses of VP/AZ therapy and on day 1 of the first and second in Group I received postremission induction therapy consisting courses of the POMP regimen (total number of doses, 6). To 2 patients with CNS disease at diagnosis, two additional doses of high-dose Ara-C (3 g/m , four doses) and L-asparaginase given monthly for four courses followed by etoposide given once were given intrathecally on days 13 and 22 of the first induction every 4 weeks for four courses; the classic POMP regimen course. (prednisone given on days 1–5, vincristine given on day 1, methotrexate given intravenously on days 1–5, and 6-mercap- topurine given intravenously on days 1–5); and finally Ara-C Definitions and statistics alone (200 mg/m2 given by continuous infusion on days 1–5) for four courses. In the second phase (Group II), instead of DAT Complete remission was defined as less than 5% blast cells in (2 þ 5 þ 5), high-dose Ara-C (total, six doses) and L-asparaginase the marrow after the second course of induction therapy. was administered as the second induction course; the post- Patients with M2A marrow (5–25% blast cells) after the second remission therapy of Group II was same as that administered to course of induction therapy proceeded to the next phase of Group I. therapy, but their disease had to be in complete remission after In POG 8821 trial,7 for postremission therapy patients were the completion of the third course of induction therapy before randomly assigned to chemotherapy or autologous BMT, consolidation therapy could begin. patients with matched family donors were eligible for allogeneic Event-free survival (EFS) was calculated from the date of BMT. The patients assigned to the chemotherapy group received registration to the date of last follow-up or first event (failure to multidrug consolidation courses. The patients who underwent achieve remission, resistant leukemia, relapse in any site, autologous BMT had bone marrow harvested after recovery second malignancy, or death due to any cause). Overall survival from the first course of etoposide/azacytidine (VP/AZ) therapy; (OS) was based on the length of time until death. The date of the harvested marrow was purged by treatment with registration marked the beginning of EFS and OS for the entire 4-hydroxycyclophosphamide at a concentration of 100 mg/ml group; the date of remission marked the beginning of disease- and an incubation hematocrit of 5–10%; the patients were free survival (DFS). Actuarial curves showing EFS and OS prepared for autologous BMT by treatment with a standard estimates and DFS estimates were constructed according to the busulphan/cyclophosphamide regimen. The study was amended Kaplan–Meier method. The relative risks were estimated by in 1990 (with approval from the data monitoring committee) to using the Cox proportional hazard’s model. The association of exclude the randomized assignment of children with Down’s covariates and response was tested by the logistic regression syndrome to groups that undergo allogeneic BMT or autologous method. Differences in EFS and OS between two or more groups BMT. were tested for statistical significance by the log rank test In POG 9421, patients without matched related donors according to the intention-to-treat principle. The homogeneity 2 received three courses of consolidation chemotherapy. Assign- of proportion was tested by the w test. For the partitioning ment to the group that received consolidation therapy (con- analysis, the covariates were analyzed by univariate methods solidation courses I and III) was accomplished by 2 Â 2 and by the recursive partitioning and amalgamation methods to randomization at initial diagnosis to stratified standard and assess their degree of association with EFS. The partitioning and cyclosporine A (CsA)-containing arms. Consolidation course II amalgamation analysis is based on Cox’s regression model that was the same for all patients. Patients assigned randomly to includes three independent variables, an indicator for one of the standard treatment arms in POG 9421 received etoposide binary covariates and two time-dependent treatment indicators. 9 (100 mg/m2) as a daily 1-h infusion for 5 days, mitoxantrone Details are described in the publication by Chang et al. All (10 mg/m2) as a daily 30-min infusion on days 1–4, and Ara-C reported P-values are two-sided. (40 mg/m2) intrathecally on day 1. With appropriate hydration and antiemetic therapy, this therapy was administered on an outpatient basis in some cases. Patients assigned randomly to Results CsA treatment arms received continuous-infusion CsA with modified doses of etoposide (60 mg/m2 per day) given by 1-h Initial features of patients enrolled on POG 8101, 8498, infusion for 5 days and mitoxantrone (6 mg/m2 daily) given as a and 8821 daily 30-min infusion on days 1–4. These doses were 60% of the standard dose, and the reduction was based on pharmacokinetic Patient characteristics, FAB phenotype, and cytogenetic features data that demonstrated that the clearance of etoposide and are shown in Table 3a and b. Table 3a gives data of all patients mitoxantrone was reduced by 40% when both agents were except those with Down’s syndrome. Table 3b shows data of administered with high doses of CsA.8 Administration of patients younger than 15 years.

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2107 Table 3 (a) Results for all eligible patients without Down’s syndrome according to different risk parameters in POG AML Studies 8101, 8498, and 8821. (5-year EFS and 5-year OS only for n410) (b) Results for eligible patients without Down’s syndrome, younger than 15 years at diagnosis, according to different risk parameters in POG AML studies 8101, 8498, and 8821. (5-year EFS and 5-year OS only for n410)

8101 8498 8821

N ( %) EFS (s.e.) OS (s.e.) N (%) EFS (s.e.) OS (s.e.) N (%) EFS (s.e.) OS (s.e.)

(a) N 257 274 615 Sex Male 137 (53.3) 16.3 (33) 26.2 (3.9) 151 (55.1) 21.8 (3.5) 33.0 (3.9) 332 (54) 28.0 (2.6) 38.7 (2.7) Female 120 (46.7) 22.3 (3.8) 26.6 (4.1) 123 (44.9) 28.0 (4.4) 37.4 (4.5) 283 (46) 34.8 (2.9) 42.3 (3.0)

Race White 182 (70.8) 20.4 (3.1) 28.4 (3.5) 197 (71.9) 27.7 (3.4) 37.5 (3.5) 421 (68.5) 33.8 (2.4) 43.4 (2.5) Black 41 (16.0) 19.5 (6.2) 22.0 (6.5) 45 (16.4) 16.4 (6.1) 28.6 (7.0) 98 (15.9) 28.5 (4.9) 37.5 (5.1) Hispanic 19 (7.4) 6.1 (5.9) 21.1 (9.4) 17 (6.2) 12.5 (8.3) 17.6 (9.2) 63 (10.2) 27.0 (5.6) 33.3 (5.9) Other 15 (5.8) 20.0 (10.3) 20.0 (10.3) 15 (5.5) 19.6 (12.4) 40.0 (12.6) 33 (5.4) 12.1 (5.7) 22.6 (7.5)

Age (years) o2 38 (14.8) 24.5 (7.1) 31.6 (7.5) 41 (15.0) 45.4 (8.4) 53.7 (8.4) 122 (19.8) 22.4 (3.9) 32.8 (4.3) 2–9 102 (39.7) 15.7 (3.6) 21.6 (4.1) 113 (41.2) 22.4 (4.2) 35.4 (4.5) 239 (38.9) 34.4 (3.1) 44.7 (3.3) 10–21 117 (45.5) 20.9 (4.0) 28.8 (4.4) 120 (43.8) 19.6 (3.8) 28.3 (4.2) 254 (41.3) 32.1 (3.1) 39.9 (3.2)

Leukocytes o20K 135 (52.5) 18.8 (3.5) 27.2 (3.9) 142 (51.8) 24.1 (3.8) 32.2 (4.0) 319 (51.9) 31.6 (2.7) 40.6 (2.8) 20–99K 86 (33.5) 19.7 (4.4) 26.6 (5.0) 78 (28.5) 31.9 (5.7) 48.7 (5.8) 211 (34.3) 32.9 (3.4) 41.1 (3.5) X100K 36 (14.0) 20.3 (6.8) 22.2 (6.9) 54 (19.7) 15.3 (5.0) 22.2 (5.7) 85 (13.8) 24.7 (4.9) 37.6 (5.3)

CNS 215 (100) 222 (100) 534 (100) Positive 6 (2.8) FF14 (6.3) 28.6 (12.1) 5.0 (13.4) 27 (5.1) 33.3 (9.1) 48.1 (9.6) Negative 209 (97.2) 17.3 (2.7) 24.7 (3.1) 208 (93.7) 26.3 (3.3) 35.0 (3.4) 507 (94.9) 32.4 (2.2) 40.9 (2.2)

FAB Types 238 (100) 268 (100) 493 (100) M1/M2 110 (46.2) 16.9 (3.6) 25.2 (4.3) 128 (47.8) 20.1 (3.8) 32.0 (4.2) 217 (44.0) 33.4 (3.4) 40.0 (3.4) M3 16 (6.7) 25.0 (12.5) 23.4 (11.8) 9 (3.4) FF41 (8.3) 31.7 (7.6) 48.8 (8.0) M4 80 (33.6) 23.1 (4.9) 32.5 (5.3) 78 (29.1) 34.5 (5.8) 46.0 (5.9) 96 (19.5) 36.5 (5.0) 47.9 (5.2) M5 29 (12.2) 17.2 (7.0) 17.2 (7.0) 40 (14.9) 20.7 (6.5) 27.5 (7.1) 89 (18.1) 21.1 (4.5) 28.7 (5.1) M6 2 (0.8) FF4 (1.5) FF9 (1.8) FF M7 1 (0.4) FF7 (2.6) FF32 (6.5) 25.0 (7.7) 34.4 (8.4) Granulocytic 0 (0.0) FF2 (0.7) FF9 (1.8) FF sarcoma

Karyotypesa 483 (100) t(8;21) 57 (11.8) 44.6 (6.8) 50.9 (6.7) inv(16) 29 (6.0) 59.7 (9.8) 75.9 (8.3) t(15;17) 55 (11.4) 20.0 (5.4) 40.0 (6.6) Normal 109 (22.6) 42.2 (4.8) 50.4 (4.9) 11q23b 56 (11.6) 23.2 (5.6) 32.1 (6.2) t(9;11) 35 (7.2) 19.6 (7.2) 31.4 (8.2) Miscc 89 (18.4) 34.8 (5.1) 37.1 (5.2) +21 7 (1.4) FF +8 10 (2.1) FF À7 9 (1.9) FF t(3;5) 5 (1.0) FF t(6;9) 6 (1.3) FF t(1;22) 4 (0.8) FF t(8;16) 3 (0.6) FF t(10;11) 9 (1.9) FF

(b) N 219 231 511 Sex Male 115 (52.5) 16.9 (3.6) 26.0 (4.2) 124 (53.7) 20.3 (3.9) 34.6 (4.4) 270 52.8 27.3 (2.8) 39.1 (3.0) Female 104 (47.5) 21.4 (4.0) 24.9 (4.3) 107 (46.3) 28.6 (4.7) 38.3 (4.8) 241 (47.2) 36.9 (3.2) 44.7 (3.3)

Race White 158 (72.2) 20.0 (3.3) 27.0 (3.6) 167 (72.3) 28.6 (3.7) 38.8 (3.9) 346 (67.7) 34.1 (2.6) 44.5 (2.7) Black 34 (15.5) 20.6 (6.9) 23.5 (7.3) 35 (15.2) 14.8 (6.1) 28.6 (7.6) 81 (15.9) 33.4 (5.6) 41.6 (5.6) Hispanic 15 (6.9) 7.3 (7.0) 20.0 (10.3) 15 (6.5) 14.3 (9.4) 20.0 (10.3) 54 (10.6) 27.8 (6.1) 35.2 (6.5) Other 12 (5.5) 16.7 (10.8) 16.7 (10.8) 14 (6.1) 21.0 (8.4) 42.9(13.2) 30 (5.9) 10.0 (5.5) 21.5 (7.8)

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2108 Table 3 Continued

8101 8498 8821

N ( %) EFS (s.e.) OS (s.e.) N (%) EFS (s.e.) OS (s.e.) N (%) EFS (s.e.) OS (s.e.)

Age o2 years 38 (17.4) 24.5 (7.1) 31.6 (7.5) 41 (17.8) 45.4 (8.4) 53.7 (8.4) 122 (23.9) 22.4 (3.9) 32.8 (4.3) 2–9 years 102 (46.6) 15.7 (3.6) 21.6 (4.1) 113 (48.9) 22.4 (4.2) 35.4 (4.5) 239 (46.8) 34.4 (3.1) 44.7 (3.3) 10–21 years 79 (36.1) 21.0 (4.8) 27.6 (5.4) 77 (33.3) 19.1 (4.6) 28.6 (5.1) 150 (29.4) 35.5 (4.0) 44.3 (4.2)

Leukocytes o20 K 121 (55.3) 20.1 (3.7) 27.9 (4.2) 119 (51.5) 22.5 (4.0) 31.0 (4.3) 263 (51.5) 32.7 (2.9) 42.0 (3.1) 20–99 K 65 (29.7) 17.2 (4.7) 23.0 (5.4) 70 (30.3) 33.0 (6.0) 50.0 (6.2) 171 (33.5) 33.3 (3.7) 42.0 (3.9) X100 K 33 (15.1) 19.0 (7.0) 21.2 (7.1) 42 (18.2) 19.8 (6.3) 28.6 (7.0) 77 (15.1) 26.0 (5.1) 40.2 (5.7)

CNS 184 (100) 184 (100) 447 (100) Positive 5 (2.7) FF13 (7.1) 30.8 (12.8) 53.8 (13.8) 25 (5.6) 32.0 (9.3) 48.0 (10.0) Negative 179 (97.3) 17.0 (2.9) 23.3 (3.3) 171 (92.9) 26.6 (3.6) 35.6 (3.7) 422 (94.4) 32.9 (2.4) 41.8 (2.5)

FAB Types 203 (100) 226 (100) 403 (100) M1/M2 92 (45.3) 13.4 (3.6) 22.5 (4.5) 99 (43.8) 18.4 (4.2) 31.3 (4.7) 172 (42.7) 34.6 (3.7) 42.4 (7.8) M3 15 (7.4) 26.7 (13.2) 25.0 (12.5) 9 (4.0) FF28 (6.9) 32.1 (9.4) 50.0 (9.8) M4 65 (32.0) 25.7 (5.5) 32.3 (5.8) 71 (31.4) 35.9(6.1) 47.8 (6.2) 80 (19.9) 36.6 (5.5) 50.0 (5.7) M5 28 (13.8) 17.9 (9.2) 17.9 (7.2) 36 (15.9) 23.1 (7.2) 30.6 (7.7) 74 (18.4) 22.7 (5.1) 30.4 (5.7) M6 2 (1.0) FF4 (1.8) FF9 (2.2) FF M7 1 (0.5) FF5 (2.2) FF32 (7.9) 25.0 (7.7) 34.4 (8.4) Granulocytic 0 (0.0) FF2 (0.9) FF8 (2.0) FF sarcoma

Karyotypesd 398 (100) t(8;21) 45 (11.3) 52.2 (7.7) 60.0 (7.4) inv(16) 24 (6.0) 55.2 (10.7) 75.0 (9.1) t(15;17) 39 (9.8) 20.5 (6.5) 41.0 (7.9) Normal 88 (22.1) 44.3 (5.4) 52.2 (5.4) 11q23b 52 (13.1) 23.1 (5.8) 32.7 (6.4) t(9;11) 32 (8.0) 18.2 (7.4) 31.3 (8.6) Miscc 73 (18.3) 37.0 (5.7) 39.7 (5.7) +21 7 (1.8) FF +8 5 (1.3) FF À7 8 (2.0) FF t(3;5) 4 (1.0) FF t(6;9) 6 (1.5) FF t(1;22) 4 (1.0) FF t(8;16) 3 (1.0) FF t(10;11) 8 (2.0) aKaryotypes were not assessed in POG 8101 and POG 8498. The discrepancy between the counts in the table and that in the paper by Raimodi, et al10 is due to the fact that five secondary AML patients were excluded in the paper by Raimondi, et al. bOther than t(9;11). cMiscellaneous abnormalities. dKaryotypes were not assessed in POG 8101 and POG 8498.

Overall outcome in POG studies 8101, 8498, 8821, and ities of OS and EFS for patients younger than 15 years are given 9421 in Figure 4.

The outcome data (Table 4a and b) include results of AML Early Deaths: The rate of early death (ie, death during patients without Down’s syndrome. To facilitate comparisons induction therapy) remained relatively constant in studies 8101, with the outcomes observed in studies conducted by the Berlin– 8498, and 8821 (Table 4a and b). The nonresponse rate was Frankfurt–Muenster (BFM) and Medical Research Council (MRC) slightly high in POG 8101, primarily for patients randomly groups, the results of patients younger than 15 years of age are assigned to the vincristine, Ara-C, and dexamethasone arm. As shown separately in Table 4b. The numbers of CNS relapses as noted in the primary publication about POG 8101, the randomi- first event were 13, 10, and 23 for 8101, 8498, and 8821, zation between the vincristine, Ara-C, and dexamethasone arm respectively. The results of the POG 9421 study are still under and the DAT arm was stopped once the early results identified the evaluation; hence, the information from this study is preliminary relatively poor outcome of patients who received the standard type and incomplete. Kaplan–Meier plots for EFS and OS for the of induction therapy used to treat ALL (61 vs 82%; P ¼ 0.02). entire group as well as those for patients younger than 15 years are based on data from only the POG 8101, 8498, and 8821 studies. As shown in Figures 2–5, the probabilities of OS and EFS Deaths in remission (see Table 4a and b): Four deaths have improved in the three consecutive studies. The probabil- occurred during remission in POG 8101. Only one of 285 of all

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2109 Table 4 (a)Outcome of all eligible patients without Down’s syndrome enrolled on POG AML studies 8101, 8498, and 8821. (b) Outcome of eligible patients without down-syndrome, younger than 15 years at diagnosis, and enrolled on POG AML studies 8101, 8498, and 8821

Number of patients 8101 8498 8821

257 274 615

n%n%n%

(a) Response evaluable 247 272 615 Complete response 202 81.8 214 78.7 476 77.4 Partial response 2 0.8 15 5.5 45 7.3 No response 35 14.2 9 3.3 65 10.6 Progressive disease 0 0 15 5.5 5 0.8 Early death 8 3.2 19 7.0 24 3.9

Off-study for patients who achieved 173 100 184 100 371 100 remission Non-CNS relapse 94 54.3 122 66.3 258 69.5 CNS relapse 12 6.9 7 3.8 21 5.7 Second malignancy 1 0.6 0 0.0 2 0.5 Toxicity 8 4.6 8 4.3 9 2.4 Death in CR 4 1.6 1 0.5 39 10.5 Patient refusal 7 4.0 3 1.6 1 0.3 Lost to follow-up 9 5.2 18 9.8 38 10.2 Other 28 16.2 25 13.6 3 0.8

Allogeneic BMT 16 6.4 15 5.5 86 13.9

EFS probability At 5 years 19.3 (2.5) 24.5 (2.8) 31.1 (1.9) At 10 years 16.3 (2.6) 24.1 (3.0) 30.5 (2.4)

OS probability At 5 years 26.3 (2.8) 35.0 (2.9) 40.4 (2.0) At 10 years 22.9 (3.0) 32.6 (3.1) 38.3 (2.5)

(b) Number of patients 219 231 511 Response evaluable 210 229 511 Complete response 172 81.9 177 77.3 395 77.3 Partial response 2 1.0 15 6.6 40 7.8 No response 30 14.3 7 3.1 53 10.4 Progressive disease 0 0 13 5.7 5 1.0 Early death 6 2.9 17 7.4 18 3.5

Off-study For patients who achieved 147 100 152 100 305 100 remission Non-CNS relapse 83 56.5 105 69.1 220 72.1 CNS relapse 10 6.8 6 3.9 20 6.6 Second malignancy 1 0.7 0 0.0 2 0.7 Toxicity 8 5.4 3 2.0 7 2.3 Death in CR 11 7.5 0 0.0 23 7.5 Patient refusal 7 4.8 1 0.7 1 0.3 Lost to follow-up 8 5.4 16 10.5 30 9.8 Other 19 12.9 21 13.8 2 0.7

Allogeneic BMT 10 4.8 13 5.7 68 13.3

EFS probability (7s.e.) At 5 years 19.1 (2.7) 25.2 (3.0) 31.9 (2.1) At 10 years 16.5 (2.9) 24.7 (3.2) 31.2 (2.7)

OS probability (7s.e.) At 5 years 25.4 (3.0) 36.3 (3.2) 41.8 (2.2) At 10 years 22.9 (3.3) 34.0 (3.4) 39.3 (2.8) s.e., standard error. patients enrolled on POG 8498 died during remission of those patients transplanted on this study. On the 8821 study, which receiving chemotherapy only, and none of children under 15 incorporated autologous and allogeneic transplantation pro- years of age. Transplantation was not integral to the study and spectively, the number of deaths in remission are as follows: 4/ therefore we do not have accurate information of deaths among 117 (3.4%) on randomized chemotherapy arm; 14/115 (12.2%)

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2110 OS: ALL PATIENTS 100 Study 8101 Study 8498 80 Study 8821

60

40 Probability (%) 20

0 01 2 3 4 5 6 7 8 9 10111213141516171819202122 Years

Figure 2 Overall survival probabilities of all patients enrolled on POG 8101, POG 8498, and POG 8821.

100 EFS: ALL PATIENTS Study 8101 Study 8498 80 Study 8821

60

40 Probability (%) 20

0 01 2 3 4 5 6 7 8 9 10111213141516171819202122 Years

Figure 3 Event-free survival probabilities of all patients enrolled on POG 8101, POG 8498, and POG 8821.

on randomized autologous BMT; 7/89 (7.9%) for patients Distinct results of POG 8498 assigned to allogeneic BMT. The POG 8498 trial established the feasibility of administering high-dose Ara-C during the second induction course and Trends in patients undergoing BMT: The number of intensification.4 There was no cerebellar toxicity associated children undergoing allogeneic BMT in POG 8821 was twice with the four-dose schedule of high-dose Ara-C (3 g/m2 per that of patients undergoing the same procedure in POG 8101 dose), whereas acute cerebellar toxicity was noted in three and 8498; this increase reflects the changing practice of early of the 174 courses of high-dose Ara-C therapy (3 g/m2; allogeneic BMT during first remission of AML in the United total number of doses 6) given to 113 patients. The outcome States. Since the POG 8821 study was among the first studies to associated with the use of high-dose Ara-C as a second course systematically require early evaluation of all registered patients of induction therapy was slightly better than that associated to determine whether they were eligible for allogeneic BMT, the with the use of standard DAT as a second course, but the proportion of AML patients to undergo allogeneic BMT in this difference was not significant (5-year EFS estimates, 27 vs 22%; study (13.7%) reflects the current proportion of children with P ¼ 0.33. AML that eventually proceed to matched donor BMT in the Another important finding of this study was the identification United States. for the first time of the superior outcome of children with Down’s syndrome; all 14 children with Down’s syndrome treated on this protocol are alive and free of disease at the time Distinct results of POG 8101 that the original paper describing this finding was written.6 Further this study included the first comprehensive review The POG 8101 study established that in childhood AML a of immunophenotying in childhood AML; the results demon- 3 þ 7 þ 7 combination of anthracyclines, Ara-C, and 6-TG yields strated the reliability of expression of CD33 and CD13 for rates of remission induction and EFS that are superior to those immunophenotypic diagnosis of AML.5 The study also showed generated by the use of an induction regimen originally that blast cells from a large proportion of patients with designed to treat ALL. The complete remission rate associated AML (61%) expressed at least one lymphoid-associated antigen, with DAT was superior (82 vs 61%; P ¼ .02). Overall, the DFS most commonly CD4, CD7, or CD19; acute promyelo- estimates after remission for the best combination of induction cytic leukemia blasts lacked CD34 and that the expression and continuation therapy combination (DAT induction and four of CD14 was positively correlated with FAB M4 or M5 cycle maintenance) were 32% at 3 years and 29% at 5 years. morphology.5

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2111 a 100 OS: AGE<15 Study 8101 Study 8498 80 Study 8821

60

40 Probability (%) 20

0 01 2 3 4 5 6 7 8 9 10111213141516171819202122 Years

b 100 EFS: AGE<15 Study 8101 80 Study 8498 Study 8821 60

40 Probability (%) 20

0 01 2 3 4 5 6 7 8 9 10111213141516171819202122 Years

Figure 4 Overall survival probabilities (a) and event-free survival probabilities (b) of patients younger than 15 years enrolled on POG 8101, POG 8498, and POG 8821.

a 100 OS: AGE ≥15 Study 8101 80 Study 8498 Study 8821 60

40 Probability (%) 20

0 01 2 3 4 5 6 7 8 9 101112131415161718192021 Years

b 100 EFS: AGE ≥15 Study 8101 80 Study 8498 Study 8821 60

40 Probability (%) 20

0 01 2 3 4 5 6 7 8 9 101112131415161718192021 Years

Figure 5 Overall survival probabilities (a) and event-free survival probabilities (b) of patients 15 years of age or older enrolled on POG 8101, POG 8498, and POG 8821.

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2112 Distinct results of POG 8821 t(16;16), in 6.0%. The group with an inv(16)/t(16;16) had the best 5-year OS estimate (68710.3%), and the groups with a The primary aim of the POG 8821 study was to compare the normal karyotype or a t(8;21) had 5-year OS estimates of 50 and safety and efficacy of autologous BMT early in first remission 46%, respectively. The reliability of cytogenetic data for with those of intensive chemotherapy. The study identified prognosis in childhood AML was further confirmed by a more several practical issues related to the conduct of a randomized updated analysis of patients who were enrolled on POG 8821 multi-institutional study of autologous BMT for children with and received chemotherapy alone (patients with Down’s AML. For example, 38% of the patients were not randomly syndrome were excluded). The best EFS estimates were those assigned to a treatment group: 16% were excluded from of patients with an inv(16)/t(16;16). Together with the OS randomization because of the lack of a matched allogeneic findings cited above, the analysis suggested that, after relapse, donor; 11.6%, because of a lack of insurance authorization for salvage therapy is more effective in patients with an inv(16) than autologous BMT; 10.4%, because of miscellaneous reasons. Of in those with other abnormalities.10,11 the 343 patients eligible for randomization, 110 (32%) chose to Partitioning analysis was prompted by the need to redefine receive chemotherapy alone rather than participate in rando- prognostic markers in childhood AML because of the emerging mization. In all, 232 patients were randomly assigned to practice of distinct treatment approaches for patients with APL treatment groups: 117 to the group that received only intensive and for those who have Down’s syndrome and AML. A recursive chemotherapy and 115 to the group that received autologous partitioning analysis of patients treated on the POG 8821 study BMTs. Using an intent-to-treat principle of analysis, the was conducted after data from children with Down’s syndrome researchers found no advantage for autologous BMT over or APL were excluded.9 After prognostic factors were identified intensive chemotherapy alone.7 Primary contributors to the lack by univariate analysis, a partitioning and amalgamation analysis of success of autologous BMT were the relatively high rate of was performed. Higher remission rates were seen for patients treatment regimen-related mortality (15% with autologous BMT older than 2 years (P ¼ 0.026), for female patients (P ¼ 0.053), vs 2.7% with intensive chemotherapy alone, P ¼ 0.05) and and for patients with an inv(16) or a t(8;21) (P ¼ 0.002). delayed bone marrow recovery after VP/AZ treatment during Conversely, lower remission rates were seen for patients with which AML in several patients relapsed; these relapses were M5 subtypes of AML (P ¼ 0.028) and for patients with counted as events in this intent-to-treat analysis. chromosome abnormalities other than an inv(16) and t(8;21) The other important contributions of this study were detailed (P ¼ 0.047). When the prognostic variables and treatment cytogenetic evaluation and the development of a partitioning variables were combined in the partitioning amalgamation model for risk-group identification based on clinical parameters analysis three groups of patients were shown to have different and cytogenetic features (described in detail below). EFS probabilities. Female patients with an inv(16), a t(8;21), or normal chromosomes had the best outcome, and male patients with an inv(16), a t(8;21), or normal chromosomes had the Distinct results of POG 9421 second best outcome. A second analysis of outcomes of patients (excluding those The data collected from this study are undergoing evaluation. with APL or with Down’s syndrome and AML and those Preliminary analyses showed that no advantage was provided by undergoing BMT) enrolled on POG 8101, 8498, and 8821 high-dose DAT during induction therapy or by CsA during indicated that the use of high-dose Ara-C in the second specific postinduction therapy. When the outcomes of all induction course resulted in a better outcome for patients in treatment groups were analyzed together, it was determined 8498 than in 8101; however, there was no significant difference that patients receiving both experimental interventions (high- between the outcomes seen in POG 8498 and 8821. This lack of dose DAT and CsA had a better EFS estimate than those treated difference indicates the large contribution of allogeneic BMT with standard dose DAT induction therapy and no CsA (3 year and Down’s syndrome to the trend toward improved survival in EFS, 36.275 vs 22.774.2%; P ¼ 0.036). However, the P-value successive childhood AML studies. does not reach the level of statistical significance by a multiple testing procedure. Results of children with Down’s syndrome: Starting with the POG 8498 study, data from Down’s syndrome patients with AML were analyzed separately from the data of other patients. Risk factors As noted earlier, the 14 patients treated on POG 8498 remained disease-free. This high success rate of patients with Down’s Starting with POG 8101, central review of morphology was syndrome continued to be observed in POG 8821, although required. Unlike BFM studies, POG studies have not separately with the more intensified treatment, there were more deaths in recorded data indicating the presence or absence of Auer rods; remission: the EFS 5-year estimates in 8821 trial exceeded 66%. therefore, it is not possible to use the BFM risk-group definitions The outcome of Down’s syndrome patients with AML is shown to reclassify patients enrolled on POG studies. However, the in Figure 7. availability of cytogenetic data from a large cohort of patients permitted POG researchers to develop risk-group definitions by using a partitioning analysis. Cytogenetic studies were not Discussion prospectively performed either POG8101 or 8498 studies and thus no data on cytogenetics are available on these two studies. The results of the sequential POG studies described in the Complete cytogenetic data were available of 483 patients preceding sections demonstrated a stepwise increase in long- enrolled on POG 8821; the cohort was the largest ever from a term survival as therapy was intensified.3 The most striking single study of childhood AML. Normal karyotypes were change was seen in the POG 8101 study, in which a therapy observed in blast cells from 109 patients (22.6%); 11q23 consisting of anthracyclines and Ara-C resulted in a rate of abnormalities were seen in blast cells from 11.6% of patients; remission induction and EFS estimates better than those resulting the t(8;21), in 11.8%; the t(15;17), in 11.4%, and the inv(16)/ from the treatment originally designed for ALL. Three groups of

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2113 patients seemed to have a superior outcome in later studies: and Ara-C (100 mg/m2 twice a day for 10 days or a total of those with Down’s syndrome,6 those with an inv(16),9,11 and 2000 mg/m2 in MRC 10,). Moreover, daunorubicin was adminis- those who were treated with matched-sibling BMT. tered as a bolus on days 1–3 in the POG studies, whereas it was Despite intensification of remission induction therapy by the given by continuous infusion in the DCTER regimen of CCG use of high-dose Ara-C during the second induction course studies, as a split dose over 30 min twice a day on days 3–5 in in POG 8498 and POG 8821, the percentages of deaths due the BFM studies and over 6 h on days 1, 3, and 5 in MRC 10. to toxicity during induction were low (4% in POG 8498 and It is of interest that in vitro studies showed that at least 90 min 6% in POG 8821). The same trend was noted in POG 9421 in of exposure to anthracyclines is required for their optimal which additional intensification of therapy occurred with the intercalation into DNA.15 However, the results of POG 8821 use of high-dose Ara-C as part of the first remission induction were superior to those resulting from the use of the standard- course. timing DCTER regimen of CCG 2891, in which the dose The 15-year OS estimates improved from 20% in the POG intensity during the first induction course was less than that used 8101 study to 40% in POG 8821. The same trends in OS and in POG 8821. These comparisons suggest that (1) a total EFS were noted when the comparison was based on age: daunorubicin dosage o100 mg/m2 (such as that used in the patients younger than 15 years fared better than those 15 years CCG 2891 standard-timing regimen) is associated with a lower of age or older. Contributing factors to the improved survival remission rate as well as lower EFS and OS estimates, (2) estimates were the use of therapy specifically designed to treat infusion of daunorubicin over 30 min or more yields results AML; the use of more intensive postremission induction therapy, superior to those provided by bolus administration, (3) a total including the use of matched-sibling BMT; and improved dose of Ara-C in excess of 1 g/m2 or a total exposure period of 10 supportive care. A review of dose intensification of Ara-C and days yields results superior to those provided by the standard daunorubicin across the four POG studies showed the pivotal dose of 100 mg/m2 administered daily for 7 days, and (4) high- contribution of Ara-C. The outcomes of groups that received dose Ara-C given early after remission induction yields results chemotherapy only and did not include patients with Down’s superior to those resulting from treatment with standard-dose syndrome in the POG 8498 and 8821 studies were not Ara-C. significantly different, despite a doubling of the cumulative In POG studies dose intensification of Ara-C either during dose of daunorubicin in POG 8821 (average doses in POG 8498 induction or postremission phase was associated with improved and POG 8821, were 185 and 360 mg/m2, respectively) (Table 2 results but not dose intensification of daunorubicin. Compared and Figure 6). It may very well be that the greatest contribution to POG 8101, significant dose intensification occurred in from anthracyclines occurs during the first course of induction POG 8498, 8821 and 9421 with clear improvement in out- therapy and that there is only a marginal contribution to OS by come. On the other hand despite a dose intensification of additional dose intensification of anthracyclines during post- daunorubicin from 135 mg/M2 in POG 8498 to 360 mg/M2 remission induction phases. in POG 8821 no significant improvement in outcome was In general, improvements in outcome were observed in evident when patients with Down’s syndrome and those successive POG studies, but the OS and EFS estimates in the undergoing BMT were excluded. It is of note that, in vitro drug POG 8821 study are somewhat lower than those observed in the resistance studies show better correlation of cytotoxicity to contemporary MRC 10 trial,12 the BFM 87 trial,13 and the Ara-C with risk for relapse in AML than cytotoxicity to Children’s Cancer Group (CCG) 2891 study, in which an daunorubicin.16 intensively timed Dexamethasone, cytarabine, thioguanine, The recent POG studies did not routinely give CNS radiation etoposide, and rubidomycin (daunorubicin) (DCTER) regimen to any group of patients. Despite this lack of treatment, CNS was tested.14 The POG 8821 study used the standard 3 þ 7 þ 7 disease was not the most frequent cause of relapse, even in induction regimen of daunorubicin (total, 125 mg/m2), Ara-C patients with CNS disease at diagnosis.10 A recent review noted (total dose per course, 700 mg/m2), and 6-TG (700 mg/m2); the better outcome in those with CNS disease at diagnosis; CNS regimens in the BFM, MRC, and CCG studies used considerably disease at diagnosis is more common in those with good greater total dose intensification of both daunorubicin (eg, prognosis cytogenetics and this appears to account for the 180 mg/m2 in the BFM 87 and 150 mg/m2 MRC 10 studies) paradoxical outcome effect.17 Therefore, it is unclear whether

EFS: Excluding DS and BMT- 8101, 8498, 8821 100 Study 8101 80 Study 8498 Study 8821 60

40 Probability (%) 20

0 01 2 3 4 5 6 7 8 9 10111213141516171819202122 Years

Figure 6 Event-free survival probabilities of patients who did not have Down’s syndrome and did not undergo allogeneic bone marrow transplantation. These patients were enrolled on studies POG 8101, POG 8498, and POG 8821.

Leukemia Pediatric Oncology Group studies of acute myeloid leukemia Y Ravindranath et al 2114 Overall Survival of Down Syndrome Patients AML 8101, 8498, 8821 & 9421 100

80

60

40 Study 8101

Probability (%) Study 8498 20 Study 8821 Study 9421 0 01 2 3 4 5 6 7 8 9 1011121314151617181920 Years

Figure 7 Overall survival probabilities of patients with Down’s syndrome and AML enrolled on POG 8101, POG 8498, POG 8821, and POG 9421.

CNS radiation as given in the BFM and MRC regimens (for those subgroups and often there is no aplasia at day 14; thus many of with CNS disease at diagnosis) would have had an additive the patients removed because of high proportion of abnormal effect in improving the outcome in the POG studies. promyelocytes at day 14 on POG 8821 may have gone on to The results of patients with Down’s syndrome (Figure 7) achieve CR at day 28. The same may have been the case for showed that the small cohort treated on POG 8498 had the patients with 11q23 abnormalities who had a particularly poor best outcome. In subsequent studies the outcome was some- outcome in POG8821 compared to other studies; the inclusion what inferior, perhaps reflecting the increased toxicity from of etoposide in the first induction course as performed in the considerable increases in anthracycline dose. In BFM CCG2891, BFM, MRC10, and the Nordic Society of Pediatric studies with a higher dose intensity of anthracylines compared Hematology and Oncology (NOPHO) studies may also be to POG 8498, there was a higher mortality among DS important for this subgroup.12,33–35 In POG studies, subgroup children compared to non-DS children18 suggesting that reduc- analysis based on FAB classification was less reliable in a tion in treatment related mortality should be major goal in partioning model, presumably because of the overlap with the therapy of DS children with AML.19 The biochemical cytogenetics which are straightforward.9 As in the NOPHO basis of the unique chemosensitivity of AML in Down’s syn- studies,36 the POG studies found that female sex is a predictor drome was studied by investigators POG and other groups20–23 of good outcome after corrections for the cytogenetic results and the reader is referred to some recent reviews on the are made.9,36 Other prognostic parameters such as drug resis- subject.24–26 tance, MDR1 expression and the role of further intensification In POG AML studies, for non-DS patients the best results were of induction therapy are under evaluation, and we expect observed with allogeneic BMT. There was however a lack of any futures studies to provide additional information about prognosis apparent benefit from autologous BMT in first CR in the and treatment. Additional contributing prognostic factors are multicenter randomized POG 8821 study. This was in large pharmacogenomic differences in various populations under part due to the rather high treatment-related mortality (TRM) and study.37 as well from patients relapsing while waiting for autologous BMT, both of which were included as events in the intent to treat 7 Conclusions: The major observations from POG AML studies design of the study. With longer observation there was no are (1) cytarabine dose intensification improves results in crossing over of the EFS curves, thus the negative impact of TRM childhood AML (2) cytogenetics are best predictors of response was still evident. The results of POG 8821 are similar to the and risk for relapse (3) children with Down’s syndrome and AML COG 2891 in this respect and as well with a large randomized 14,27 constitute a special subgroup of children with AML and have a adult AML study. On the other hand, at least three recent high cure rate (4) allogeneic BMT in first remission with reports, albeit from nonrandomized studies, suggest that Matched sibling donors continues to offer best chances for cure autologous BMT performed in first remission may improve the in non-DS AML but this option is available for only a small over all outcome in childhood AML, if the TRM could be fraction of children with AML (5) comparison with other reduced under 3%.28–30 Thus, the question of when and whom 31,32 contemporary studies suggests that additional improvement in to transplant in AML remains unsettled. outcome may be achieved with a more pharmacodynamic Cytogenetic characteristics have emerged as the most based dosing of daunorubicin in the initial remission induction important predictor of outcome in childhood AML in our studies course. and in others. After data of patients with Down’s syndrome and with APL were excluded, the best outcome was observed for patients with an inv(16) þ t(16;16) with 5-year EFS of 60% and Acknowledgements OS of 76% and the next best outcome was in patients with a t(8;21) or with a normal karyotype (see Table 3a and b). The This work was supported in part by Grant nos. CA-03161, CA- remaining groups had the poorest outcomes. The EFS rates were 05587, CA-07431, CA-11233, CA-15525, CA-15525, CA-15898, lower for APL cases in part due to the requirement of evaluation CA-69177, CA-20549, CA-25408, CA-28383, CA-28439, CA- of marrow response at day 14; as is now well recognized the 28476, CA-29691, CA-28476, CA-29139, CA-29293, CA-30969, kinetics of response in APL are quite different from other CA-32053, CA-33587, CA-33603, CA-33625, CA-41573,

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