Donor killer cell immunoglobulin-like receptor (KIR)-ligand incompatibility is associated with decreased relapse incidence (RI) and improved leukemia-free survival (LFS) after haploidentical and HLA-mismatched unrelated hematopoietic stem cell transplantation. We assessed outcomes of 218 patients with acute myeloid leukemia (AML n ¼ 94) or acute lymphoblastic leukemia (n ¼ 124) in complete remission (CR) who had received a single-unit unrelated cord blood transplant (UCBT) from a KIR-ligand-compatible or -incompatible donor. Grafts were HLA-A, -B or -DRB1 matched (n ¼ 21) or mismatched (n ¼ 197). Patients and donors were categorized according to their degree of KIR-ligand compatibility in the graft-versus-host direction by determining whether or not they expressed HLA-C group 1 or 2, HLA-Bw4 or HLA-A3/-A11. Both HLA-C/-B KIR-ligand-and HLA-A-A3/-A11 KIR-ligand-incompatible UCBT showed a trend to improved LFS (P ¼ 0.09 and P ¼ 0.13, respectively). Sixty-nine donor-patient pairs were HLA-A, -B or -C KIR-ligand incompatible and 149 compatible. KIR-ligandincompatible UCBT showed improved LFS (hazards ratio ¼ 2.05, P ¼ 0.0016) and overall survival (OS) (hazards ratio ¼ 2.0, P ¼ 0.004) and decreased RI (hazards ratio ¼ 0.53, P ¼ 0.05). These results were more evident for AML transplant recipients (2-year LFS and RI with or without KIR-ligand incompatibility 73 versus 38% (P ¼ 0.012), and 5 versus 36% (P ¼ 0.005), respectively). UCBT for acute leukemia in CR from KIR-ligandincompatible donors is associated with decreased RI and improved LFS and OS.

UCBT is a viable treatment for adults with advanced lymphoid malignancies. Chemosensitive disease, use of low-dose TBI, and higher cell dose were factors associated with significantly better outcome.