Comparison of Allogeneic Transplant Outcomes Between Matched Sibling Donors and Alternative Donors in Patients Over 50 Years of Age with Acute Myeloid Leukemia: 8/8 Allele-Matched Unrelated Donors and Unrelated Cord Blood Provide Better Leukemia-Free Survival Compared with Matched Sibling Donors During Nonremission Status

: Acute myeloid leukemia (AML) is the most common indication for allogeneic hematopoietic cell transplantation (HCT). The increased availability of alternative donor sources has broadened donor types for older patients without HLA-matched sibling donors (MSD). It is uncertain if an MSD should be the first option for allogeneic HCT in patients with AML over 50 years of age. : The objective of this study was to compare survival and other posttransplant outcomes between MSDs, 8/8 allele-matched unrelated donors (MUDs), 7/8 allele-MUDs, unrelated cord blood (UCB), and haploidentical donors for patients with AML over 50 years of age. : We conducted a retrospective study to compare outcomes in 5,704 patients with AML over 50 years of age and receiving allogeneic HCT between 2013 and 2021, using either MSD, 8/8 allele-MUD, 7/8 allele-MUD, UCB, or haploidentical donors in Japan. Complete remission (CR) and non-remission at HCT were analyzed separately for all analyses. : In total, 3041 patients were CR, and 2663 patients were non-remission at the time of HCT. In multivariate analysis, donor type did not determine overall survival, irrespective of disease status at HCT. Leukemia-free survival (LFS) was significantly better for 8/8 allele-MUD (hazard ratio [HR], 0.77; 95% confidence interval [CI], 0.64 to 0.93; P = 0.005) and UCB (HR, 0.76; 95% CI, 0.65 to 0.88; P = 0.001), but not for 7/8 allele-MUD (HR, 0.97; 95% CI, 0.79 to 1.19; P=0.794), and haploidentical donor (HR, 0.86; 95% CI, 0.70 to 1.05; P=0.146) compared to the MSD group in non-remission status. However, donor type did not determine LFS among CR status. Relapse rates were significantly lower for 8/8 allele-MUD and UCB, whereas non-relapse mortality was higher for UCB compared to the MSD group among both CR and non-remission status. : Our registry-based study demonstrated that MSDs do not lead to superior survival compared to alternative donors for patients with AML over 50 years of age. Furthermore, 8/8 allele-MUDs and UCB provide better LFS compared with MSDs during non-remission status. Therefore, MSD is not necessarily the best donor option for allogeneic HCT in this population.