Comparable outcomes between unrelated and related donors after reduced-intensity conditioning allogeneic hematopoietic stem cell transplantation in patients with high-risk multiple myeloma.

The purpose of this study was to assess the results of allogeneic stem cell transplantation (allo-SCT) after reduced-intensity conditioning (RIC) from matched related donors (MRD) and unrelated donors (URD) in 40 patients with high-risk multiple myeloma (MM) in a single centre. Seventeen (43%) (Group 1) and 23 patients (57%) (Group 2) had URD and MRD, respectively. Thirty-nine patients (98%) received one or more autologous transplantation. The median follow-up was 22 months (1-49). None of our patient experienced a graft rejection. The cumulative incidence of grade II-IV acute GVHD was higher (47%) for the URD vs. (17%) for the MRD (P = 0.092). The cumulative incidence of chronic GVHD was no different between the two groups (24% vs. 30%, respectively). At 2 yr, the TRM probabilities were lower in the unrelated group 12% vs. 22% in the related group (P = 0.4). Also at 2 yrs, for patients receiving unrelated transplantation overall and progression-free survivals, 59% and 42%, respectively compared to patients with related donor transplantation, 66% and 44% (P = 0.241). In conclusion, these results suggest that URD in MM is feasible. The small number of patients with URD emphasizes the need to delineate indications and perform prospective protocols.