Donor selection may contribute to improve clinical outcomes of T cell-replete haploidentical stem cell transplantation (Haplo-SCT) with post-transplant cyclophosphamide (PT-Cy). Impact of second-degree related donor (SRD) was not fully elucidated in this platform. We retrospectively compared the outcome of patients receiving Haplo-SCT either from a SRD (n = 31) or a first-degree related donor (FRD, n = 957). Median time to neutrophil and platelet recovery did not differ between a SRD and a FRD transplant (p = 0.599 and 0.587). Cumulative incidence of grade II–IV acute graft-versus host disease (GVHD) and moderate-severe chronic GVHD was 13% and 19% after SRD vs 24% (p = 0.126) and 13% (p = 0.395) after FRD transplant. One-year cumulative incidence of non-relapse mortality (NRM) was 19% for SRD and 20% for FRD (p = 0.435) cohort. The 3-year probability of overall survival (OS) and progression-free survival (PFS) was 42% vs 55% (p = 0.273) and 49% vs 35% (p = 0.280) after SRD and FRD transplant, respectively. After propensity score adjustment or matched pair analysis, the outcome of patients receiving Haplo-SCT from a SRD or a FRD did not differ in terms of NRM, OS, PFS, acute and chronic GVHD. Our results suggest that a SRD is a viable option for Haplo-SCT with PT-Cy when a FRD is not available.
