Hematopoietic Stem Cell Transplantation in Pediatric Acute Myelogenous Leukemia: Relevance of the Stem Cell Source to the Transplant Outcome

ABSTRACT

BACKGROUND: Postremission therapy is critical for achieving long-term survival in the patients with acute myelogenous leukemia (AML). Allogeneic bone marrow transplantation during the first complete remission (CR) with using a HLA-identical sibling donor may offer the best chance for long-term leukemia-free survival. The patients without matched siblings have several treatment options. The aim of this study was to compare the clinical outcomes after matched sibling transplantation (MST), unrelated stem cell transplantation (non-MST), or autologous peripheral blood stem cell transplantation (APBSCT) as a postremission therapy for children with AML. METHODS: Thirty four hematopoietic stem cell transplantations (SCT) in 32 children with AML were performed between June, 1996 and December, 2004. Two patients who failed at prior APBSCT underwent a 2nd unrelated transplantations. The disease status at the time of transplantation, the conditioning regimen, prophylaxis for graft-versus-host disease (GVHD), the incidence of GVHD, complications, the cause of death, the over-all survival and the event-free survival were retrospectively compared in relation to the stem cell sources. RESULTS: There were 19 males and 13 females with a median age of 8 yr 10 mo. The median follow-up was 17 mo. Twenty-eight cases were transplanted during CR1. Most (5/6) of patients other than the patients who were in CR1 were allocated in the non-MST group. APBSCT was done in 17 cases, and allo-transplants were done in 17 cases, which included MSTs in 10, matched-unrelated BM transplants in 5, haploidentical CD34+selected peripheral blood transplant in 1, and 1-antigen mismatch unrelated cord blood transplantation in 1. Acute GvHD > or = than Grade 2 was found in 20% of the MST cases vs. 85.7% in the non-MST cases (P<.01). The two-year cumulative relapse risks were 46.4% in the APBSCT cases, 20% in the MST cases and 31.5% in the non-MST cases. The Kaplan-Meier 2-year EFS in all cases was 55.7%: 46.3% in the APBMT cases, 80.0% in the MST cases and 68.6% in the non-MST cases, despite the higher proportion of high risk patients in the non-MST group. CONCLUSION: This study indicated that MST was the best option for pediatric AML. For patients without matched siblings, the patients with unrelated transplants fared better, had better survival and a lower relapse rate than the APBSCT patients. However, a further prospective, randomized study that incorporates a larger number of patients and a cord blood transplant arm is necessary to definitely determine the best option for pediatric AML.