BACKGROUNDWide application of umbilical cord blood transplantation (UCBT) in adult patients is limited by low cell-dose available in one umbilical cord blood (UCB) unit. The aim of this study was to investigate the safety and long-term outcomes of UCBT from unrelated donors in adult and adolescent patients with leukemia.

METHODSThirteen patients with leukemia received double-unit UCBT with human leukocyte antigen (HLA) mismatched at 0 - 2 loci. We analyzed the engraftment, graft-versus-host disease (GVHD) and survival.

RESULTSTwelve evaluable patients (92.3%) had neutrophil and platelet engraftment at a median of 21 days (range, 16-38 days) and 34 days (range, 25 - 51 days), respectively. At day 30, engraftment was derived from one donor in 8 patients (66.7%, 95%CI 40.0% - 93.4%), and from both donors in 4 patients (33.3%, 95%CI 6.7% - 60.0%) with 1 unit predominated. Unit with larger nucleated cell (NC) dose would predominate in engraftment (P = 0.039), whereas CD34(+) cell dose or HLA-match failed to demonstrate any relationship with unit predominance. Only one patient developed grade II acute graft-versus-host disease (aGVHD). Chronic GVHD (cGVHD) was observed in 2 of 11 patients who survived more than 100 days, and both were limited. The median follow-up after transplantation for the 13 patients was 45 months (range 1.5 - 121.0 months) and 72 months (range 41.0 - 121.0 months) for the 8 alive and with full donor chimerism. The 5-year cumulative disease free survival (DFS) was (61.5 ± 13.5)%. Of the 13 patients, 5 patients died in 1 year and 1-year transplantation related mortality (TRM) was 23.1% (95%CI 0.2% - 46.0%).

CONCLUSIONDouble-unit UCBT from unrelated donors with HLA-mismatched at 0-2 loci may overcome the cell-dose barrier and be feasible for adults and adolescents with leukemia.