Can Cord Blood Unit Selection Improve Outcomes After Single-Unit Unrelated Cord Blood Transplantation for Non-Remission Acute Myeloid Leukemia?

BACKGROUND: Allogeneic hematopoietic cell transplantation (HCT) is the only established curative therapy for acute myeloid leukemia (AML) refractory to chemotherapy. Unrelated umbilical cord blood transplantation (CBT) provides a valuable alternative donor source for these patients, but whether cord blood unit selection can improve outcomes after single-unit CBT in non-remission AML remains uncertain. METHODS: We retrospectively analyzed 3256 adult patients with non-remission AML who underwent single-unit CBT as their first allogeneic HCT between 1998 and 2023 in Japan, using data from the nationwide Japanese Data Center for Hematopoietic Cell Transplantation. Cord blood-related factors, including cryopreserved total nucleated cell (TNC), CD34⁺ cell, and colony-forming unit-granulocyte/macrophage (CFU-GM) doses, HLA mismatches, and donor-recipient sex and ABO compatibilities, were evaluated for their associations with overall survival (OS), leukemia-free survival (LFS), relapse, non-relapse mortality (NRM), hematopoietic recovery, and graft-versus-host disease (GVHD). RESULTS: In multivariable analyses, a CD34⁺ cell dose ≥0.608 × 10⁵/kg was associated with decreased overall mortality compared with