Abstract
Conflicting reports exist regarding the impact of extramedullary disease (EMD) at diagnosis upon outcomes after allogeneic hematopoietic cell transplantation (HCT) in children and young adults with acute myeloid leukemia (AML). We retrospectively analyzed the effect of EMD at diagnosis on post-HCT outcomes in a large cohort of children and young adults (21 and younger) who had AML and received their first myeloablative allogeneic HCT for AML during 2008 to 2019 (N = 938; 52% males). Data were obtained from the Center for International Blood and Marrow Transplant Research database. Patients were grouped based on EMD at diagnosis as bone marrow (BM) involvement only (Group I; n = 630); BM + central nervous system (CNS) involvement (Group II; n = 212), and BM + other EMD ± CNS (Group III n = 96). All patients were in a morphologic complete remission (CR) with no evidence of EMD pre-HCT. Outcomes compared included 3-yr progression-free survival (PFS), overall survival (OS), non-relapse mortality (NRM), and relapse incidence (RI). Group III patients were younger at HCT (Group III median age 3, versus age 11 in Group I, and age 10 in Group II) and more often had high Pediatric Disease Risk Index scores (52% in Group III versus 22% in Group I and 25% in Group II). At a median follow-up of 70 mo (range 3-155 mo), the 1-yr and 3-yr PFS, NRM, RI, and OS were similar among all 3 groups on univariate analysis. On multivariable analysis, the presence of EMD was associated with decreased RI: Group II, with a hazard ratio (HR) of 0.70 (95% CI, 0.52-0.94; P = .020) and Group III with an HR of 0.70 (95% CI, 0.46-1.05; P = .086) compared to Group I. There was no difference in PFS (P = .21), NRM (P = .27), and OS (P = .82) among the groups. In our study, in patients with AML who proceeded to HCT in CR, the presence of EMD at diagnosis was not associated with adverse outcomes or increased relapse risk.