Late outcomes after posttransplant cyclophosphamide-based GVHD prophylaxis in patients with AML: an ALWP-EBMT study

Data on late events after allogeneic hematopoietic stem cell transplantation (allo-HSCT) with posttransplant cyclophosphamide (PT-Cy)-based graft-versus-host disease (GVHD) prophylaxis in patients with acute myeloid leukemia (AML) remain very limited. We analyzed long-term outcomes in 1289 patients from the European Society for Blood and Marrow Transplantation registry who underwent PT-Cy-based allo-HSCT for AML in first remission from haploidentical (n = 906), 10/10 matched unrelated donors (MUD, n = 208), or matched sibling donors (MSD, n = 175), and who remained leukemia-free 2 years after transplantation. At 2 years from the landmark, the cumulative incidence of relapse and nonrelapse mortality (NRM) was 6% and 4% in haploidentical, 7% and 3% in MUD, and 8% and 4% in MSD recipients, respectively. Similarly, 2-year estimates of leukemia-free survival and overall survival were 91% and 93% for haploidentical, 90% and 95% for MUD, and 88% and 93% for MSD recipients, respectively. No statistically significant association was found between donor type and long-term transplantation outcomes. In contrast, transplantation from a female donor to a male recipient (hazard ratio [HR], 2.70; P = .013) and older donor age (HR per 10-year increase, 1.34; P = .036) were associated with increased risk of late NRM. These associations were confirmed in subanalyses in the haploidentical cohort. Notably, no factors associated with late relapse were identified in the multivariable models. PT-Cy-based allo-HSCT is associated with favorable outcomes in patients with AML who remain leukemia-free 2 years after transplant. Long-term outcomes after haploidentical allo-HSCT were comparable with those of 10/10 MUD or MSD recipients in the setting of PT-Cy GVHD prophylaxis.