Impacts of donor age and HLA mismatch on HCT outcomes differ according to the donor CMV serostatus in unrelated allo-HCT.

In unrelated allogeneic hematopoietic cell transplantation (allo-HCT), older and/or HLA-mismatched donors are known risk factors for survival outcomes. In healthy individuals, cytomegalovirus (CMV) seropositivity is associated with impaired adaptive immune systems. We assessed whether the adverse effects of donor risk factors are influenced by the donor CMV serostatus. We analyzed 5836 patients with CMV seropositivity who received unrelated allo-HCT. We divided the entire cohort into 2 cohorts according to the donor CMV serostatus: CMV positive (DP) and negative (DN). We also stratified each cohort into 4 groups based on donor age (aged ≥40 or <40 years) and HLA parity (8/8 or 7/8): Young88 and Old88, and Young78 and Old78, respectively. In the CMV-DP cohort, the Old88 (hazard ratio [HR], 1.20; P = .012), Young78 (HR, 1.35; P < .001), and Old78 (HR, 1.60; P < .001) groups were associated with inferior overall survival (OS) than the Young88 group. In contrast, in the CMV-DN cohort, neither donor age nor HLA disparity was associated with inferior OS. The adverse impact of donor age was different between the cohorts (CMV-DP: HR, 1.19; P = .001; CMV-DN: HR, 1.04; P = .53; P for interaction, .070), as was the impact of HLA (CMV-DP: HR, 1.34; P < .001; CMV-DN: HR, 1.08; P = .23; P for interaction, .012). The impacts of donor age and HLA mismatch on OS might differ according to the donor CMV serostatus. In unrelated allo-HCT from a CMV-seronegative donor, an HLA-mismatched older donor may be able to be selected without affecting OS.