LAUSR

Background Optimal myeloablative conditioning (MAC) in the setting of haploidentical hematopoietic cell transplantation (haplo-HCT) with post-transplant cyclophosphamide (PTCy) is unknown. We studied the outcomes of total body irradiation (TBI) vs. chemotherapy (CT) based MAC regimens in acute myelogenous leukemia (AML) pts undergoing haplo-HCT and reported to EBMT. Methods The study included 1008 AML pts who underwent haplo-HCT during 2010-2018, following TBI (n=89, 9%) or CT (n=919, 91%) based MAC. Regimen intensity was defined by EBMT criteria and the cases with busulfan dose Results In univariate analysis, day 100 incidence of acute GVHD (aGVHD) II-IV and III-VI was 22% vs. 27% (p-0.44) and 12% vs. 12% (p-0.92) in TBI and CT cohorts, respectively. Two-yr total and severe chronic GVHD (cGVHD) incidence were 42% vs. 27% (p In a subgroup analysis of pts Conclusions In this large relatively homogenous cohort of AML patients who received haplo-HCT with PTCy, TBI based MAC was associated with higher incidence of overall cGVHD without impacting other transplant outcomes compared to CT based MAC. A prospective study is needed to validate these findings.