Effect of extramedullary disease on allogeneic hematopoietic cell transplantation for pediatric acute myeloid leukemia: a nationwide retrospective study.

Children with acute myeloid leukemia (AML) commonly develop extramedullary disease (EMD), which comprises central nervous system (CNS) lesions and myeloid sarcoma (MS). In this retrospective analysis, we aimed to determine the effect of EMD on the outcomes of allogeneic hematopoietic cell transplantation (HCT) in 678 pediatric patients with de novo AML (median age, 7 years; range, 0.3-15 years) between 2006 and 2016. We compared the outcomes between patients with (EMD group, n = 158; CNS lesion, n = 47, CNS lesion + MS, n = 9, and MS, n = 102) and without EMD at diagnosis (non-EMD group, n = 520). Survivors were followed for a median of 4.5 years, and the 4-year overall survival (OS) rates were 60.6% and 56.4% in the EMD and non-EMD groups, respectively (P = 0.60). No significant differences in OS were observed with respect to the EMD site, except bone lesions, which were associated with poor OS after HCT in a non-remission status. A multivariate analysis revealed that EMD did not affect the outcomes of HCT. In conclusion, the study findings suggest that EMD should not be considered a poor prognostic factor in HCT for children with AML.