Haploidentical vs matched unrelated donor transplantation for acute myeloid leukemia in remission: A prospective comparative study

Despite comparable outcomes of haploidentical transplants (Haplo‐HSCT) with HLA‐matched unrelated transplants (MUD‐HSCT) in retrospective comparisons, few studies have prospectively compared Haplo‐HSCT with MUD‐HSCT in AML. Here, we prospectively compared the outcomes of Haplo‐HSCT with MUD‐HSCT for AML in remission (n = 110) to prove non‐inferiority of overall survival in Haplo‐HSCT. Both groups were well balanced in factors related to biological features of AML and measurable residual disease (MRD) status by Wilms' tumor gene 1 (WT1) assay. A unique, reduced‐toxicity preparative regimen was used for Haplo‐HSCT, whereas mostly‐myeloablative regimen was for MUD‐HSCT. Both groups showed similar patterns of neutrophil and platelet recovery, whereas delayed T‐cell reconstitution in Haplo‐HSCT was found compared with MUD‐HSCT. No significant differences were found in acute or chronic graft‐vs‐host‐disease (GVHD) and post‐transplant infectious events with an exception of EBV or CMV infection, which occurred more frequently in Haplo‐HSCT. After a median follow‐up of 47 months, no significant differences in overall survival (65% vs 54%, P = .146), disease‐free survival (67% vs 53%, P = .142), relapse (20% vs 21%, P = .858), non‐relapse mortality (14% vs 26%, P = .103), or GVHD‐free/relapse‐free survival (54% vs 41%, P = .138) were observed for Haplo‐HSCT vs MUD‐HSCT. In multivariate analysis, WT1 expression before transplantation independently predicted relapse, resulting in inferior survival. Separate analysis of unenrolled patients (n = 110) who were excluded or refused to participate in this study showed consistent results with enrolled patients. This prospective study demonstrated the non‐inferiority of Haplo‐HSCT to MUD‐HSCT for AML in remission, and validated the role of WT1 quantification as an MRD marker (ClinicalTrial.gov identifier: NCT01751997).