Impact of HLA Disparity in Haploidentical Bone Marrow Transplantation Followed by High Dose Cyclophosphamide

We studied the impact of HLA mismatching on the outcome of 318 consecutive patients who received an un-manipulated haploidentical bone marrow transplant, followed by post-transplant cyclophosphamide (PT-CY). The number of HLA mismatched antigens was tested for its impact on overall survival (OS) and non relapse mortality (NRM), whereas HLA mismatches in the graft versus host (GvH) direction were tested for prediction of GvHD and relapse; finally, we studied whether graft rejection correlated with the number of HLA mismatched antigens in host versus graft (HvG) direction. Two-hundred and thirty-one donor/recipient pairs (72%) had 4/8 mismatches at the A, B, C, DRB1 HLA loci. HLA mismatches did not predict the 2 years OS(HR 0.83, p=0.58) and NRM(SHR 1.08, p=0.93). The cumulative incidence of aGvHD (p=0.13), 1-year cGvHD (p=0.84), and relapse rate (p=0.26) did not correlate with univectorial GvH mismatches. Similarly,no correlation was observed between the amount of HLA mismatch in the HvG direction and graft rejection. In multivariate analysis, advanced disease at transplant was the strongest predictor of survival, NRM, relapse, and graft rejection.