Abstract
<title>Abstract</title> <p> Data on allogeneic hematopoietic stem cell transplantation (allo-HSCT) for pediatric acute myeloid leukemia, myelodysplasia-related (AML-MR) remain limited. We retrospectively analyzed 732 children and adolescents who underwent first allo-HSCT for AML-MR (n = 252) or AML, defined by differentiation (AML-DD; n = 480) between 2000 and 2018, using Japanese nationwide registry data. The 5-year leukemia-free survival and overall survival (OS) did not differ significantly between AML-MR and AML-DD (44.5% versus 48.2% and 52.6% versus 51.1%, respectively). Within AML-MR, outcomes were heterogeneous: monosomal karyotype (MK) without − 7/del(7q) was associated with inferior OS compared with AML-DD, whereas MK with − 7/del(7q) was not. Among patients with MK, those with − 7/del(7q) had better OS than those without (71.1% versus 31.0%, <italic>P</italic> = 0.023). A cytogenetics-based three-tier risk model stratified AML-MR outcomes (5-year OS: 63.6%, 51.1%, and 31.8% for low-, intermediate-, and high-risk groups, <italic>P</italic> < 0.001). Non-remission at HSCT and poor performance status independently predicted inferior survival. Although overall allo-HSCT outcomes in pediatric AML-MR were comparable to AML-DD, subgroup heterogeneity—particularly the adverse impact of MK without − 7/del(7q)—warrants risk-adapted strategies. </p>