Outcome of 154 patients with severe aplastic anemia who received transplants from unrelated donors: the Japan Marrow Donor Program.

We retrospectively analyzed results for 154 patients with acquired severe aplastic anemia who received bone marrow transplants between 1993 and 2000 from unrelated donors identified through the Japan Marrow Donor Program. Patients were aged between 1 and 46 years (median, 17 years). Seventy-nine donor-patient pairs matched at HLA-A, -B, and -DRB1 loci, as shown by DNA typing. Among the 75 mismatched pairs, DNA typing of 63 pairs showed that 51 were mismatched at 1 HLA locus (18 HLA-A, 11 HLA-B, 22 HLA-DRB1) and 12 were mismatched at 2 or more loci. Seventeen patients (11%) experienced either early or late graft rejection. The incidence of grade III/IV acute graft versus host disease and chronic graft versus host disease was 20% (range, 7%-33%) and 30% (range, 12%-48%), respectively. Currently, 99 patients are alive, having survived for 3 to 82 months (median, 29 months) after their transplantations. The probability of overall survival at 5 years was 56% (95% confidence interval, 34%-78%). Multivariate analysis revealed the following unfavorable factors: transplantation more than 3 years after diagnosis (relative risk [RR], 1.86; P =.02), patients older than 20 years (RR, 2.27; P =.03), preconditioning regimen without antithymocyte globulin (RR 2.28; P =.04), and HLA-A or -B locus mismatching as determined by DNA typing. Matching of HLA class I alleles and improvement of preparative regimens should result in improved outcomes in patients with severe aplastic anemia who receive transplants from unrelated donors.