Who is the best allogeneic hematopoietic stem cell transplant donor for severe aplastic anemia? Data from the Chinese Bone Marrow Transplantation Registry Group (CBMTRG).

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for severe aplastic anemia (SAA), with donor sources including matched sibling donors (MSDs), haploidentical donors (HIDs), and unrelated donors (URDs). However, the optimal criteria for donor selection remain undefined. We performed a multicenter retrospective study of 795 consecutive SAA patients who underwent allo-HSCT between 2012 and 2020 across 11 transplant centers in China. The overall survival (OS), failure-free survival (FFS), and GVHD-free/FFS (GFFS) rates were 85.2%, 83.6%, and 76.1%, respectively. Donor-related variables including relationship, age, sex match, blood type, and HLA mismatches were evaluated. Multivariable Cox regression identified donor age ≥50 years as an independent risk factor for inferior GFFS (HR = 2.13), OS (HR = 2.09), and FFS (HR = 2.18) (all P < 0.001). To directly compare the prognostic weight of donor age versus HLA compatibility, we stratified patients into four subgroups according to donor type (HID vs. MSD) and donor age (<50 vs. ≥50 years). Kaplan-Meier analysis with log-rank testing revealed that recipients of haploidentical grafts from younger donors achieved superior OS and FFS compared with those transplanted from older HLA-matched sibling donors. These findings demonstrate that donor age has a greater influence on transplant outcomes than HLA matching. With continuous improvements in haploidentical transplantation techniques, selecting younger haploidentical donors may represent a more favorable strategy than choosing older matched sibling donors.