Impact of donor type on allo-HSCT outcomes in MRD-positive AML: An EBMT registry study

Results from a multicenter, retrospective, European Society for Blood and Marrow Transplantation (EBMT) registry study, evaluating outcomes with different donor types for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with measurable residual disease (MRD)-positive acute myeloid leukemia (AML; N = 3,385) in first or second complete remission (CR), were published in Experimental Hematology & Oncology by Ye et al.

Key data: Patients received grafts from a haploidentical (HAPLO; n = 609), matched sibling (MSD; n = 1,057), or matched unrelated (MUD; n = 1,719) donor. All patients in the HAPLO cohort received post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GvHD) prophylaxis, compared with 11.4% and 8.6% in the MSD and MUD cohorts. At a median follow-up of 2.1 years, relapse incidence (RI) was higher with MSD (hazard ratio [HR], 1.55; 95% confidence interval [CI], 1.26–1.91; p < 0.01) and MUD (HR, 1.26; 95% CI, 1.03–1.54; p = 0.03) transplant vs HAPLO transplant. Patients in the MSD cohort had inferior leukemia-free survival (LFS; HR, 1.19; 95% CI, 1.01–1.41; p = 0.048), but lower non-relapse mortality (NRM; HR, 0.63; 95% CI, 0.46–0.84; p = 0.004), vs those in HAPLO cohort. No significant difference was observed in LFS between MUD and HAPLO cohorts, or in overall survival (OS) across all donor types.

Key learning: In this study, HAPLO allo-HSCT with PTCy-GvHD prophylaxis was associated with lower RI vs MSD and MUD allo-HSCT, but this did not translate into an OS advantage. Prospective studies using PTCy uniformly across all donor types are needed to determine whether the relapse benefit observed with HAPLO transplant is independent of PTCy.