Alternative donor transplantation for myelodysplastic syndromes: haploidentical relative and matched unrelated donors

We compared outcomes in 603 patients with myelodysplastic syndrome (MDS) after HLA-haploidentical relative (n = 176) and HLA-matched unrelated (n = 427) donor hematopoietic cell transplantation (HCT) from 2012 to 2017, using the Center for International Blood and Marrow Transplant Research database. All transplantations used reduced-intensity conditioning regimens. Total-body irradiation plus cyclophosphamide and fludarabine was the predominant regimen for HLA-haploidentical relative donor HCT, and graft-versus-host disease (GVHD) prophylaxis was uniformly posttransplantation cyclophosphamide, calcineurin inhibitor, and mycophenolate. Fludarabine with busulfan or melphalan was the predominant regimen for HLA-matched unrelated donor HCT, and GVHD prophylaxis was calcineurin inhibitor with mycophenolate or methotrexate. Results of multivariate analysis revealed higher relapse (hazard ratio [HR], 1.56; P = .0055; 2-year relapse rate, 48% vs 33%) and lower disease-free survival (DFS) rates after HLA-haploidentical relative donor HCT (HR, 1.29; P = .042; 2-year DFS, 29% vs 36%). However, overall survival (OS) rates did not differ between donor type (HR, 0.94; P = .65; 2-year OS, 46% for HLA-haploidentical and 44% for HLA-matched unrelated donor HCT) because of mortality associated with chronic GVHD. Acute grade 2 to 4 GVHD (HR, 0.44; P < .0001) and chronic GVHD (HR, 0.36; P < .0001) were lower after HLA-haploidentical relative donor HCT. By 2 years, probability of death resulting from chronic GVHD was lower after HLA-haploidentical relative compared with HLA-matched unrelated donor HCT (6% vs 21%), negating any potential survival advantage from better relapse control. Both donor types extend access to transplantation for patients with MDS; strategies for better relapse control are desirable for HLA-haploidentical relative donor HCT, and effective GVHD prophylaxis regimens are needed for unrelated donor HCT. •MDS patients undergoing transplantation with haploidentical relative and matched unrelated donors had similar OS rates.•Relapse was more common in patients with haploidentical donors; chronic GVHD occurred more often in those with matched unrelated donors. [Display omitted]