Donor selection in T-cell-replete haploidentical-related donor peripheral blood stem cell transplantation

The effects of donor characteristics on outcomes after T-cell-replete (TCR) haploidentical-related donor peripheral blood stem cell transplantation (PBSCT) with post-transplant cyclophosphamide (PTCy) or low-dose antithymocyte globulin (ATG) remain unclear. We evaluated the impact in 1,677 patients who received a PTCy protocol (PTCy-haplo; n = 1,107) or low-dose ATG protocol (ATG-haplo; n = 570). A low CD34 ⁺ cell dose (<4 ×10 ^6/ kg) was the only donor characteristic associated with worse overall survival (OS) after PTCy-haplo (adjusted hazard ratios [aHR] = 1.49, P = 0.008), whereas increased donor age by decade (aHR = 1.12, P = 0.008) and a large number of human leukocyte antigen mismatches (aHR = 1.46, P = 0.010) were associated with worse OS after ATG-haplo. Donor age increased the risk of grade II–IV acute graft-versus-host disease (GVHD) only after ATG-haplo (HR: 1.14, P = 0.018), whereas it increased the risk of grade III–IV acute GVHD both after PTCy-haplo (HR: 1.32, P = 0.009) and ATG-haplo (HR: 1.22, P = 0.006). Offspring donors had better relapse-free survival and GRFS than sibling donors after ATG-haplo. Our data suggest a comprehensive donor selection hierarchy after TCR haploidentical related-donor PBSCT with PTCy or low-dose ATG.