Triple post transplant cyclophosphamide (PTCY) based GVHD prophylaxis: HLA matched versus HLA haploidentical transplants.

We report a retrospective analysis of 198 allogeneic hematopoietic stem cell transplant (HSCT) recipients with post-transplant cyclophosphamide (PTCY), cyclosporine and mycophenolate mophetil as graft-versus-host-disease (GVHD) prophylaxis: the donors were HLA-matched (n = 78), or haploidentical relatives (HAPLO) (n = 120). The two groups were comparable except for older age in the HAPLO group. The main diagnosis were acute leukemia (57%) and myelofibrosis (21%). In the HLA-matched and HAPLO group the outcomes were as follows: aGVHD grade II-IV, 10% vs 27% (p = 0.005); moderate-severe cGVHD, 4% vs 19% (p = 0.004); transplant related mortality (TRM) at 1 year 10% vs 21% (p = 0.04); relapse at 1 year 24% vs 10% (p = 0.051) respectively. Disease free survival (DFS) at 1 year was 65% for matched and 68% for HAPLOs (p = 0.85). DFS and OS were independently predicted by age over 60 and higher DRI, whether the only independent predictive variable for GVHD and relapse free survival (GRFS) was age over 60. In conclusion: given the same PTCY based, GVHD prophylaxis, HLA-mismatched grafts are exposed to a higher risk of acute and chronic GVHD. This translates in increased TRM. DFS is comparable for HLA matched and HAPLO grafts.