When an HLA identical donor is not available in adults with hematological neoplasms: single-center comparison of single-unit cord blood transplantation and haploidentical-related PBSC transplantation with PTCy using a standardized conditioning platform (thiotepa-busulfan-fludarabine).

Haploidentical related (Haplo) and umbilical cord blood (UCB) donors are the main "alternative donor" options for allogeneic hematopoietic stem cell transplantation (HCT) for patients without identical donor. At our institution, UCB was the main alternative donor type until 2013, when HaploHCT was introduced as the preferred procedure. A common myeloablative conditioning regimen was used, based on thiotepa, busulfan, and fludarabine. We analyze the outcomes of 47 patients (61%) who received a single UCB transplantation (UCBT) and 30 patients (39%) who received a HaploHCT with post-transplant cyclophosphamide. No differences were found in the rate of neutrophil engraftment, whereas platelet recovery was earlier with HaploHCT. NRM was higher after UCBT at 3 months and 3 years (13% and 13% vs. 23% and 45% in HaploHCT and UCBT, respectively; p < 0.001 for both time points). The 3-year relapse incidence was 35% after HaploHCT vs. 17% after UCBT, respectively (p = 0.13). The 100-day incidence of grade 3-4 acute GVHD (3% vs. 11%) and the 3-year moderate-to-severe chronic GVHD (4% vs. 15%) did not differ between HaploHCT and UCBT, respectively (p > 0.2). There was a trend for higher overall survival at 1 and 3 years in HaploHCT recipients (69% vs. 45% and 64% vs. 38%, respectively; p = 0.055 for both time points). Despite the small sample sizes, multivariate analysis adjusted for patient age and disease status at transplant showed a better 3-year OS in HaploHCT recipients, mostly due to a lower NRM (p < 0.001). Our results support the use of HaploHCT when feasible when an identical donor is not available.