HLA Haploidentical versus Matched Unrelated Donor Transplants with Post-Transplant Cyclophosphamide based prophylaxis

Abstract

Post transplant cyclophosphamide (PTCy) graft-versus-host disease (GVHD) prophylaxis has allowed haploidentical (Haplo) transplantation to be performed with results similar to that after matched unrelated donor (MUD) transplantation with traditional prophylaxis. The relative value of transplantation with MUD versus Haplo donors when both groups receive PTCy/calcineurin inhibitor/mycophenolate containing GVHD prophylaxis is not known. We compared outcomes after 2036 Haplo and 284 MUD transplantations with PTCy GVHD prophylaxis for acute leukemia or myelodysplastic syndrome in adults between 2011 and 2018. Cox regression models were built to compare outcomes between donor types. Recipients of myeloablative and reduced intensity regimens were analyzed separately. Among recipients of reduced intensity regimens, 2-year graft failure (3% versus 11%), acute grade II-IV GVHD (HR 0.70, p=0.022), acute grade III-IV GVHD (HR 0.41, p=0.016) and non-relapse mortality (HR 0.43, p=0.0008) were lower after MUD compared to Haplo transplantation. Consequently, disease-free (HR 0.74, p=0.008; 55% versus 41%) and overall survival (HR 0.65, p=0.001; 67% versus 54%) were higher after MUD compared to Haplo transplants. Among recipients of myeloablative regimens, day-100 platelet recovery (95% versus 88%) was higher and grade III-IV acute (HR 0.39, p=0.07) and chronic GVHD (HR 0.66, p=0.05) were lower after MUD compared to Haplo transplantation. There were no differences in graft failure, relapse, non-relapse mortality, disease-free and overall survival between donor types with myeloablative conditioning regimens. These data extend and confirm the importance of donor-recipient HLA matching for allogeneic transplantation. A MUD is the preferred donor, especially for transplantations with reduced intensity conditioning regimens.