Umbilical cord blood transplantation in Chinese children with beta-thalassemia

To evaluate factors affecting outcome of sibling umbilical cord blood transplantation in Chinese children with thalassemia. The authors conducted a retrospective review of all patients undergoing such transplants in a single institution. Nine children with thalassemia major were diagnosed at a median age of 12 months. They received irregular blood transfusions and suboptimal iron chelation therapy before transplant. Sibling cord blood transplant was performed at a median of 5.5 years (range 3.5-10 years). Six donors were HLA-identical; three were one- to three-antigen mismatched. The mean number of nucleated cells infused was 6.6 x 10(7)/kg (range 3.4-12.7); the mean number of CD34+ cells infused was 3.8 x 10(5)kg (range 0.6-11.7). Seven patients had engraftment of donor cells. The median number of days to achieve a neutrophil count of > 0.5 x 10(9)/L was 19 days (range 10-25); the median number of days to achieve a platelet count of > 20 x 10(9)/L was 33 days (range 19-63). Of the six patients who received HLA-identical transplants, one developed grade 2 and two developed grade 1 acute graft-versus-host disease. Two of the three patients receiving mismatched cord blood did not achieve engraftment, and the other one engrafted but developed grade 4 acute graft-versus-host disease. Two patients subsequently developed secondary graft rejection and had autologous marrow regeneration before day 60 posttransplantation. With a median follow-up of 49 months (range 38-64), eight patients survived but only four were transfusion-independent. Umbilical cord blood transplant appears to have a higher chance of nonengraftment and secondary rejection. A more intensive immunosuppressive conditioning regimen may be required.