No Improvement of Overall-Survival in Children with High-Risk Acute Myeloid Leukemia by Stem Cell Transplantation in 1st Complete Remission.
Authors: Reinhardt Dirk , Kremens Bernhard , Zimmermann Martin , Vormoor Josef , Dworzak Michael , Peters Christine , Creutzig Ursula , Klingebiel Thomas 
Published: October 2019

Abstract
One aim of the AML-BFM 98 study was to evaluate prospectively the impact of matched sibling donor (MSD)-SCT in 1st complete remission (CR) in children with high-risk (HR)-AML.
Patients: Between 7/1998 and 3/2004 494 children and adolescents were enrolled in the studies AML-BFM 98 and the AML-BFM 98 Interim 2003. Patients with favorable cytogenetics [t(8;21), inv(16), t(15;17)], corresponding morphology (AML FAB M1/2 with Auer rods, M4eo, M3) and < 5% blasts on day 15 were defined as standard risk (SR)-group (n=177). All others were stratified to HR-group (n=317) and eligible for SCT in 1st CR. Out of 275 patients achieving 1st CR (87%) 63 patients had a MSD and 188 had no MSD (intent-to-treat group, ITT) while 24 patients had to be excluded due to missing HLA typing or initial refusal to SCT. Thirty-six patients received MSD-SCT (=as-treated group), another two children were transplanted from a matched unrelated donor (MUD) although an MSD was available. The reasons not performing SCT in 1st CR in the remaining 25 children with a donor available were early relapse (n=7), death in CR (n=2), clinical reasons (n=8), or refusal of SCT (n=8). Chemotherapy (CHT) only was given in 192 patients (n=167 without MSD, n=25 with a MSD). Another 21 children were transplanted from an unrelated donor (n=18), family donor (n=1), haploidentical donor (n=2). The reasons were slow response, very poor cytogenetics or other clinical reasons.
Treatment: All patients received double induction and consolidation. MSD-SCT in 1st was scheduled after 4 blocs of treatment. Children who were not transplanted in 1st CR received intensification and a 1-year maintenance therapy. The recommended conditioning regimen consisted in busulfan and cyclophosphamide.
Results
ITT analysis revealed no significant differences in of 5 year disease-free survival (DFS) and overall survival (OS) between children with or without a donor (no donor vs. donor: DFS 43±4% vs. 47±7% plog rank 0.52; OS 56±4% vs. 58±9%, plog rank 0.16).
The as-treated analysis gave similar results: CHT only vs. MSD-SCT: DFS 35±11% vs. 59±9% p Mantel-byar 0.13; OS 59±13% vs. 62±12%, p Mantel-byar 0.51).
The major reasons of treatment failures were relapses in all groups [CHT only n=100 (52%), MSD-SCT n=13 (34%), MUD-SCT n=9 (50%)]. A 2nd CR was achieved in 71% of the CHT only group (n=74). After SCT in 2nd CR, OS was 40±6%. By contrast, only two children (9%) of 22 children after relapse following SCT in 1st CR could be salvaged.
Severe late adverse events (e.g. severe chronic GvHD CTC grade IV, destruction of big joints, intracerebral bleedings) were more frequent in children transplanted in 1st CR (15%) than in those with CHT only (including SCT in 2nd CR; 5%, p×2< 0.05).
Conclusion: In the population-based, prospective multi-center study AML-BFM 98 allogeneic MSD-SCT in 1st CR showed no advantage in children and adolescents with HR-AML. Considering the higher toxicity of allogeneic SCT, in the ongoing trial AML-BFM 2004, this SCT (MSD or MUD) is restricted to patients in 2nd CR and refractory AML.