Haploidentical stem cell donor choice for patients with acute myeloid leukemia: A study from the ALWP of the EBMT

There is a paucity of information to guide selection of the most suitable donor in haploidentical (Haplo) hematopoietic stem cell transplantation (HSCT). For this reason, from the Acute Leukemia Working Party (ALWP) of the European Society for Blood and Marrow Transplantation (EBMT), we conducted a retrospective analysis to evaluate the impact of Haplo donor characteristics on outcomes in patients with acute myeloid leukemia (AML) who received graft-versus-host disease prophylaxis with post-transplant cyclophosphamide (PTCy). The primary endpoint was GvHD-free and relapse-free survival (GRFS). Overall, 2200 patients were included. The median age of donors was 37 years (range, 8-71), 820 (37%) were females, including 458 (21%) who were used for male recipients. Additionally, 1631 (74%) donated peripheral blood (PB). Multivariable analysis identified certain donor-related risk factors with a detrimental impact on transplant outcomes. The use of PB, older donor´s age (>37yrs) and female donors to male recipients negatively affected GRFS. Donor´s age and female donor to male recipient combination also affected non-relapse mortality, leukemia-free survival and overall survival. In conclusion, donor-related variables significantly influence AML patient outcomes following Haplo-HSCT with PTCy. When possible, younger donors and male donors for male recipients should be prioritized. The use of BM can additionally prevent GVHD.