OBJECTIVEUnrelated umbilical cord blood has the clear benefits of rapid availability and a reduced stringency of requirement for HLA match. The aim of this study was to investigate the efficacy of unrelated umbilical cord blood transplantation (UCBT) in the treatment of malignant leukemia in children.

METHODSSix children with malignant leukemia, including three cases of acute lymphocyte leukemia [two high-risk patients and one standard-risk patient in complete remission (CR)], two juvenile myelomonocytic leukemia (one in CR and one in the accelerating stage), and one acute myeloblastic leukaemia (in CR), received a UCBT. The umbilical cord blood grafts were HLA-matched (n=1) or HLA-mismatched at 1 (n=1) or 2 (n=1) or 3 (n=3) loci. Busulfan/cyclophosphamide/antithymocyte globulin (ATG) or total body irradiation (TBI)/cyclophosphamide/ATG was involved in the myeloablative pretreatment regimen. The median infused donor nucleated cell was 8.51 x 10(7)/kg of recipient weight, and the CD34+ cell was 1.81 x 10(5)/kg of recipient weight. Cyclosporin, corticoid, mycophenolate mofetil and daclizumab were used for prophylaxis of acute graft versus host disease (GVHD).

RESULTSThe time to reach an absolute neutrophil count of 0.5 x 10(9)/L ranged from 11 to 35 days (median: 13 days) and the time to reach a platelet count of 20 x 10(9)/L ranged from 27 to 68 days (median: 30 days) after transplantation, and the donors' hematopoietic stem cells were shown in these patients. Four patients developed grade I to III acute GVHD but responded to steroids and daclizumab. Chronic GVHD was not found during a 3-16-month follow-up. Four patients survived and did not relapse during the follow-up.

CONCLUSIONSUnrelated umbilical cord blood is an alternative source of hematopoietic stem cells for patients with leukemia. UCBT can tolerate 1-2 HLA mismatches. The incidence of acute GVHD is high in UCBT recipients.