Comparison of single-unit umbilical cord blood transplantation and haploidentical transplantation using posttransplant cyclophosphamide during first complete remission of acute myeloid leukemia.

Choosing an optimal alternative donor is an important clinical concern in allogeneic hematopoietic cell transplantation (HCT). In Japan, single-unit umbilical cord blood transplantation (UCBT) has been widely used in the last two decades, whereas HCT from HLA-haploidentical related donors (haplo-HCT) has been increasingly used following the advent of posttransplant cyclophosphamide (PTCY) for graft-versus-host disease (GVHD) prophylaxis. This registry-based study aimed to compare outcomes between single-unit UCBT (n = 848) and PTCY-based haplo-HCT (n = 241) performed during first complete remission in patients with acute myeloid leukemia. UCBT was associated with a lower likelihood of engraftment (P < 0.001), a higher risk of grade 2-4 and grade 3-4 acute GVHD (P = 0.003 each), and a lower risk of extensive chronic GVHD (P = 0.048). The UCBT and haplo-HCT groups did not significantly differ in 3-year probabilities of overall survival (68% versus 69%, P = 0.686), GVHD/relapse-free survival (55% versus 54%, P = 0.866), relapse (14% versus 16%, P = 0.463), and non-relapse mortality (21% versus 19%, P = 0.403), respectively, which were confirmed with multivariate analysis. These results indicate that both procedures should be considered viable options for patients lacking a matched donor.