Limited Impact of Donor-Recipient Weight Difference on Outcomes of Allogeneic Hematopoietic Cell Transplantation

Donor-recipient weight difference may be an important consideration in selection of suitable donors in allogeneic hematopoietic cell transplantation (HCT), as it can affect stem cell yield during harvesting. However, the impact of donor-patient weight difference on transplant outcomes remains largely unknown. We retrospectively analyzed 841 consecutive patients transplanted at Princess Margaret Hospital 2018-2023. The majority of patients received HCT for acute myeloid leukaemia (48.3%) or myelodysplastic syndrome (16.9%) using matched unrelated (48.5%) or matched related (23.3%) donors. The median donor/recipient weight difference was 1.3 kg (range: -82-128). Weight difference was positively correlated with CD34+ cell dose (P<0.001). A Cox proportional hazard model including weight as a continuous variable demonstrated no impact of weight difference on survival, relapse, relapse-free survival (RFS), or non-relapse mortality (NRM). In contrast, the use of heavier donors was associated with a small but significant increase in the risk of cytomegalovirus (CMV) reactivation in univariate analysis (HR 1.06, P=0.02) and chronic graft-vs-host disease (GVHD) in univariate (HR 1.07, P=0.03) and multivariate (HR 1.07, P=0.04) analyses. Patients were then divided into three groups based on the donor-recipient weight difference: <-20kg (16.2%), -20-20kg (62.8%) and >20kg (21.1%). Weight difference was positively correlated with CD34+ cell dose (P<0.001). The use of heavier donors was associated with faster absolute neutrophil count (P=0.03) but not platelet (P=0.18) engraftment. There was no effect of donor-recipient weight difference on survival, relapse, RFS, NRM, grade 2-4 and 3-4 acute GVHD, chronic GVHD, moderate-severe cGVHD, incidence of blood stream infections at day 30, or Epstein-Barr virus reactivation at 1-y (Figure 1). The use of heavier donors remained associated with the incidence of CMV reactivation at 1-y. Our data suggest that donor-recipient weight discrepancy, although associated with risk of CMV reactivation and chronic GVHD, has little impact on other major outcomes post allogeneic HCT. Therefore, donor-recipient weight difference should be given limited consideration on donor selection in allogeneic HCT.