Changes in unrelated donor usage for allogeneic hematopoietic cell transplant in Canada: 2013–2023 and identifying priorities in donor selection

BACKGROUND: Factors influencing unrelated donor selection for allogeneic hematopoietic cell transplantation (HCT) continue to shift. To understand current priorities in step-wise donor selection and guide optimal recruitment for the Canadian Blood Services Stem Cell Registry, we examined changes in donor usage for Canadian patients in 2023. MATERIALS AND METHODS: A retrospective cohort study was conducted of unrelated allogeneic donor transplants in Canada (excluding Quebec) in 2023 with comparison to previous usage and to survey results of transplant center donor selection algorithms. RESULTS: Five hundred patients (mean age 51.7 years; 62% male) underwent first transplantation with unrelated human leukocyte antigen (HLA-matched (n = 416, 83%) or mismatched adult donors in 2023. Mean donor age was 28.7 years. cytomegalovirus (CMV) concordance in 73% and avoidance of major ABO mismatch in 62% was observed. Selection of Canadian (CDN) donors for CDN patients (n = 50, 10%) is characterized by a preference for HLA-matched, young (≤ 30 years old), male registrants and is positively influenced by availability of donor CMV serostatus and ABO blood group typing at time of initial donor search. When an international donor was used despite the presence of an HLA-matched CDN option, young donor age (≤ 30 years), male sex, and CMV-matching were prioritized. Greater use of HLA-matched donors is observed compared with 2013 and donor factors influencing selection align with survey responses of Canadian transplant centers. CONCLUSION: To best serve our patients, HLA-matched CDN stem cell registrants should be young (≤ 30 years), and with CMV and ABO results available at search to facilitate timely selection.