Age-related differences in donor selection priorities for allogeneic hematopoietic transplantation

Patient age might influence donor selection priorities in allogeneic hematopoietic stem cell transplantation (allo-HCT), due to the differences in donor age, organ function, and resistance to graft-versus-host disease between younger and older patients. We compared the transplant outcomes between patients aged <50 years and those aged ≥50 years who received transplants from human leukocyte antigen (HLA)-matched related donors (M-RD, N=4,106), HLA one-antigen-mismatched related donors (1MM-RD, N=592), HLA two or three-antigen-mismatched related donors (23MM-RD, N=882), HLA-matched unrelated donors (M-UD, N=3,927), HLA one-locus-mismatched unrelated donors (1MM-UD, N=2,474), or unrelated cord blood units (U-CB, N=5,867). To assess the impact of donor age, the M-UD and 1MM-UD groups were further subclassified into younger (M-UD-Y, 1MM-UD-Y: donor age <50 years) and older (M-UD-O, 1MM-UD-O: donor age ≥50 years) donor subgroups. Among patients aged ≥50 years, overall survival in the M-UD-Y group was significantly superior to that in the M-RD group (hazard ratio=0.87, P=0.0039), whereas the M-UD-O group showed no advantage (hazard ratio=1.08, P=0.48). In this age group, 1MM-RD, 23MM-RD, and U-CB were associated with significantly inferior overall survival, while neither 1MM-UD-Y nor 1MM-UD-O was. NRM was significantly lower in the M-UD-Y group than in the M-UD-O group among patients aged ≥50 years, without increasing relapse risk. For patients aged <50 years, overall survival in the M-UD-Y and M-UD-O groups was comparable to that in the M-RD group, but 23MM-RD, 1MM-UD-Y, and U-CB were associated with inferior overall survival. Therefore, donor selection priorities in allo-HCT might differ according to recipient age. A younger M-UD might be preferred for patients aged ≥50 years.