OBJECTIVETo retrospectively study the impact of human leukocyte antigen (HLA) mtyping mismatching between donor and recipient on outcome of single unit unrelated cord blood transplantation (sUCBT).

METHODS139 patients with hematological malignancies received sUCBT in single center from May 2008 to August 2012 were analyzed. Of 139 patients at enrollment, 22 were 0 mismatched (mm), 69 1 mm, 48 2 mm by low-resolution HLA-A, -B, and high-resolution (HR) DRB1. All patients'conditioning regimen was myeloablative, and a combination of cyclosporine A (CsA) and mycophenolate mofetil (MMF) was given for graft-versus-host disease (GVHD) prophylaxis for all patients. The cohort of patients were followed-up until December 15, 2013.

RESULTSPatients of 0 mm had a statistically significant higher cumulative incidence of neutrophil engraftment by day 42 than those of 1 and 2 mm (P=0.042 and 0.002, respectively), patients of 0 mm with either a higher prefreeze total nucleated cell (TNC) dose (>5 × 10⁷/kg) or lower dose (<5 × 10⁷/kg) had a statistically significant higher cumulative incidence of neutrophil engraftment by day 42 than those of 2 mm (P=0.01 and 0.02, respectively). Patients of 0 mm had a statistically significant lower cumulative incidence of acute GVHD by day 100 than those of 1 and 2 mm (P=0.006 and 0.001, respectively). The difference of 1-year transplant-related mortality (TRM) between 0 and 2 mm patients was statistically significant (P=0.03). Patients of 2 mm received UCB units with a TNC dose less than 5 × 10⁷/kg had a higher 1-year TRM than of 0 mm patients (P=0.03). Patients of 0 mm had a statistically significant higher 3-year disease free survival (DFS) than those of 2 mm (P=0.03), compared with patients of 2 mm given CB units with a TNC dose less than 5 × 10⁷/kg, 0 mm patients and 1mm patients received UCB units with a TNC dose greater than 4 × 10⁷/kg had higher DFS rates (P=0.02 and 0.02, respectively).

CONCLUSIONThe HLA typing mismatching between donor and recipient had a great impact on neutrophil engraftment and long term DFS after sUCBT, 2mm cord blood unit with less TNC (<5 × 10⁷/kg) was not an optimum UCB graft.