Post-transplant cyclophosphamide for unrelated donor peripheral blood stem cell transplant with special attention to graft content and the impact of a higher γδ T cell dose

Abstract In this study, PtCy was used in 44 patients along with mycophenolate and tacrolimus with HLA matched (29) and mismatched (15) unrelated. The study was done to determine the impact of graft content on outcome thus all patients had flow cytometric analysis of their graft content including the number of B cells, NK cells, and various T cell subsets. Of the 15 patients with HLA mismatched donors, 12 were one antigen mismatched and 3 were 2 antigen mismatched. Sixteen (36.3%) of the patients developed acute GVHD (without any grade IV acute GVHD). For all patients the median time to ANC engraftment was 18 days while median time to platelet engraftment was 24 days. Mean estimated overall survival was 59.9 months, median overall survival was not reached. Higher γδ T cell dose was associated with the development of acute GVHD (p=0.0038). The use of PtCy in addition to MMF and tacrolimus has been shown to be a reasonable strategy to successfully engraft with unrelated donors. This method, potentially with the added intervention of selective gamma-delta T cell depletion, could increase transplant feasibility in recipient-donor combinations with greater HLA disparity and ensure that ethnic minorities have greater access to stem cell transplants.