Effect of HLA incompatibility on graft-versus-host disease, relapse, and survival after marrow transplantation for patients with leukemia or lymphoma.

We analyzed the relevance of HLA incompatibility to acute graft-versus-host disease, relapse, and survival in 281 patients with hematologic neoplasms who underwent bone marrow transplantation. Each patient received marrow from a family member who shared one HLA haplotype with the patient but differed to a variable degree for the HLA-A, -B, and -D antigens of the haplotype not shared; 29 were phenotypically identical, 119 were incompatible for one locus, 104 for two loci, and 29 for three loci. These 281 patients were compared with 967 patients who received marrow from siblings with identical HLA genotypes. All patients were treated with cyclophosphamide and total-body irradiation followed by the infusion of unmodified donor marrow cells. Occurrence of severe acute graft-versus-host disease was evaluated in patients who achieved sustained engraftment. In recipients of haploidentical grafts occurrence of severe acute graft-versus-host disease was associated with (1) graft-versus-host disease prophylaxis containing the combination of methotrexate plus cyclosporine versus standard methotrexate, relative risk = 0.35; 95% confidence interval, 0.21-0.57, p less than 0.0001; and (2) the degree of recipient HLA incompatibility, relative risk = 1.95 for each locus incompatible; 95% confidence interval, 1.52-2.50, p less than 0.0001; (3) patient age, relative risk = 1.23 per decade; 95% confidence interval, 1.05-1.44, p = 0.0094. Acute graft-versus-host disease was associated with lower leukemic relapse after transplant in patients with acute lymphocytic leukemia, and chronic graft-versus-host disease was associated with lower relapse after transplant for acute nonlymphocytic leukemia in relapse or chronic myelogenous leukemia in blast crisis. After transplantation for acute nonlymphocytic leukemia in remission, the rate of leukemic relapse was 22% in 61 recipients of "one-locus" (A, B, or D)-incompatible grafts compared to 37% in 561 recipients of HLA-identical sibling grafts. Survival was decreased as the degree of HLA disparity increased. Survival of "one-locus"-incompatible transplant recipients, however, was equivalent to that of HLA-identical sibling transplant recipients.