Comparison of haploidentical bone marrow versus matched unrelated donor peripheral blood stem cell transplantation with posttransplant cyclophosphamide in patients with acute leukemia

Purpose: Posttransplant cyclophosphamide (PTCy) is increasingly being utilized as a principle GvHD prophylaxis strategy in allogeneic hematopoietic cell transplantation (allo-HCT). A haploidentical (haplo) or matched unrelated donor (UD) is a valid option in the absence of a matched related donor. Experimental Design: We compared the outcomes of patients with acute leukemia who underwent haplo bone marrow (haplo-BM, N ¼ 401) versus UD mobilized peripheral blood stem cells (UD-PB, N ¼ 192) transplantation in the setting of PTCy. Results: The median follow-up duration was 36 months in the haplo-BM group and 16.6 months in the UD-PB group, respectively (P < 0.01). Myeloablative conditioning was used in 64.6% and 42.7% of haplo-BM and UD-PB patients, respectively (P < 0.01). Cumulative incidence of neutrophil engraftment at day 30 was 87% in haplo-BM versus 94% in UD-PB, respectively (P ¼ 0.21). In the multivariate analysis, the risk of grade 2-4 acute GvHD (HR ¼ 0.53, P ¼ 0.01) and chronic GvHD (HR ¼ 0.50, P ¼ 0.02) was significantly lower in the haplo-BM group compared with the UD-PB group. There was no significant difference between the study groups with respect to relapse incidence, nonrelapse mortality, leukemia-fee survival, overall survival, or GvHD-free and relapse-free survival. Conclusions: The use of a haplo donor with a BM graft resulted in a lower incidence of GvHD compared with a UD-PB stem cell graft in the setting of PTCy for patients with acute leukemia. However, differences in GvHD did not translate into a difference in survival outcomes. Based upon these data, UD-PB or haplo-BM should be considered equally acceptable sources for allo-HCT.