Unrelated donors are associated with improved relapse-free survival compared to related donors in patients with myelodysplastic syndrome undergoing reduced intensity allogeneic stem cell transplantation.

Reduced intensity allogeneic stem cell transplantation (RI alloSCT) is a potentially curative treatment approach for patients with myelodysplastic syndrome (MDS). It is currently unclear if older related donors are better than younger unrelated donors for patients with MDS undergoing RI alloSCT. We retrospectively studied 53 consecutive MDS patients who underwent RI alloSCT between April 2007 and June 2014 and evaluated associations between donor type and outcomes with adjustment for significant covariates. 34 patients (median age: 64 years) and 19 patients (median age: 60 years) received allografts from unrelated and related donors, respectively. Unrelated donors were younger than related donors (median age: 32 vs. 60 years, P < 0.0001). There were no significant differences in baseline disease characteristics of patients receiving allografts from related or unrelated donors. Patients who received allografts from unrelated donors had a lower relapse risk (adjusted hazard ratio [aHR] = 0.35, P = 0.012) and improved relapse-free survival (aHR = 0.47, P = 0.018). HLA mismatched unrelated donors were associated with a higher risk of grade 2-4 acute graft versus host disease (GVHD) (HR = 4.64, P = 0.002) without an accompanying increase in the risk of non-relapse mortality (P = 0.56). Unrelated donors provided a higher mean CD8 cell dose (P = 0.014) and were associated with higher median donor T cell chimerism at day 60 (P = 0.003) and day 100 (P = 0.03). In conclusion, patients with MDS who received allografts from unrelated donors had a lower risk of relapse and improved relapse-free survival when compared to patients who received allografts from related donors. These findings should be confirmed in a prospective study. Am. J. Hematol. 91:883-887, 2016.