Transplant outcomes using older matched sibling donors compared with young alternative donors: a CIBMTR analysis.

Whether older HLA-matched sibling donors (MSD) are preferred over younger alternative donors for allogeneic hematopoietic cell transplantation (allo-HCT) with posttransplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis is unclear. We compared outcomes in allo-HCT recipients ≥50 years old after HCT from an older MSD (≥50 years) with recipients of younger (≤35 years) HLA-matched unrelated donor (MUD), haploidentical related donor (haplo), and HLA-mismatched unrelated donor (MMUD), grouped based on PTCy or calcineurin-inhibitor (CNI) based GVHD prophylaxis, that were reported to the Center for International Blood and Marrow Transplant Research between 2014 and 2021. The primary end point was overall survival (OS). Among 14 662 HCT recipients, 3746 received PTCy- and 10 916 CNI-based prophylaxis. In patients receiving PTCy-based HCT, the adjusted 5-year OS was similar between MSD and other donor types: 44% after MSD versus 52% after MUD (multivariable hazard ratio [HR]: 1.20; 95% confidence interval [CI], 1.03-1.41; P = .09), 45% after haplo donor (HR, 1.02; 95% CI, 0.88-1.18; P = 1.00), and 46% after MMUD (HR, 1.00; 95% CI, 0.83-1.21; P = 1.00). Compared with MSD, use of MUD associated with improved disease-free survival (DFS) with PTCy-based (HR, 1.21; 95% CI, 1.05-1.40; P = .048) and CNI-based (HR, 1.09; 95% CI, 1.04-1.15; P < .01) prophylaxis. Haplo donor use associated with worse OS compared with MUD use with PTCy (HR, 1.18; 95% CI, 1.05-1.33; P = .04). Older MSDs result in similar OS compared with younger alternative donors; however, use of a younger MUD associated with improved DFS in older-aged recipients.