Comparison of matched sibling, unrelated and haploidentical donors in hematopoietic stem cell transplantation. A real-world experience from the Argentine Group for Bone Marrow Transplantation and Cell Therapy (GATMO-TC).

We retrospectively analyzed 570 adult patients who received allogeneic stem cell transplantation for malignant diseases. The outcomes were compared according to donor type. Most of the patients (60%) were transplanted for acute leukemia. Median follow-up was 1.6 years. Haploidentical allogeneic stem cell transplantation was more frequently performed for acute myeloid leukemia and in late stages than any other donor type. Non-relapse mortality at 100 days and one year for unrelated and haploidentical donors were similar, 19%-29% vs. 17%-28%, respectively. A significant better non-relapse mortality was observed for matched sibling donors (7%-15%; p < 0.001). Relapse rate was higher in haploidentical donors compared to matched sibling and unrelated donors (three year relapse rate 46%, 39%, 28%; respectively p < 0.001). Haploidentical donors resulted in lower three year progression-free survival and worse 3 year overall survival (32%; p < 0.001 and 42%; p < 0.001) compared with other donors (44% and 55% MSD, 40% and 42% UD, respectively). The incidence of grade II-IV acute graft-versus-host disease was higher in unrelated donors (51% unrelated, 35% haploidentical, 36% matched sibling; respectively; p = 0.001), with no difference in grades III-IV (p = 0.73) or in chronic graft-versus-host disease (p = 0.2) between groups. After multivariate analysis, haploidentical and unrelated donors remained negatively associated with non-relapse mortality (HR 1.95; 95% CI 1.10-3.20 and HR 2.70; 95% CI 1.63-4.46, respectively). Haploidentical donors were associated with a higher risk of relapse and worse overall survival. This analysis shows that haploidentical donors were associated with similar non-relpase mortality and higher relapse rates than unrelated donors. Better results in non-relapse mortality were observed for matched sibling donors.