Post-transplant cyclophosphamide versus antithymocyte-globulin as graft versus host disease prophylaxis in haploidentical transplant

Severe graft-versus-host-disease is a major barrier for non T-cell-depleted haploidentical stem cell transplantation and there is no consensus on the optimal GVHD prophylaxis. This study compared the two most commonly used graft-versus-host-disease prophylaxis regimens (post-transplant-cyclophosphamide-based (PTCY) versus the anti-thymocyte-globulin-based (ATG)) in adults with acute myeloid leukemia reported to the european society for blood and bone marrow transplantation. 308 patients were analyzed, 193 received PTCY and 115 ATG as anti- graft-versus-host-disease prophylaxis. PTCY was more likely associated to bone marrow as graft source (60% versus 40%, p=0.01). Patients in the PTCY group had significantly less grade 3-4 acute graft-versus-host-disease than those in the ATG group (5% versus 12%, respectively, p=0.01), comparable chronic graft-versus-host-disease. Multivariate analysis showed that non-relapse-mortality was lower in the PTCY group (22% versus 30%, HR 1.77(95%CI 1.09-2.86), p=0.02) with no difference in relapse incidence. Patients receiving PTCY had better GVHD-free, relapse-free-survival (HR 1.45 (95% CI 1.04-2.02), p=0.03) and leukemia-free-survival (HR 1.48 (95% CI 1.03-2.12) p=0.03) than those in ATG group. In the multivariate analysis there was also a trend for a higher overall survival (HR 1.43 (95% CI 0.98-2.09) p=0.06) for PTCY versus the ATG group. Notably, center experience was also associated with non-relapse-mortality and GVHD-free, relapse-free survival. Haplo-SCT using PTCY can achieve better leukemia-free-survival and GVHD-free, relapse-free survival, lower incidence of graft-versus-host-disease and non-relapse-mortality as compared to ATG-based graft-versus-host-disease prophylaxis in patients with acute myeloid leukemia.