Children with acute lymphoblastic leukemia who receive T-cell-depleted MLAmismatched marrow allografts from unrelated donors have an increased incidence of primary graft failure but a similar overall transplant outcome

Disparity for HLA in unrelated donor bone marrow transplantation (BMT) incr eases the risk of graft rejection and graft-versus-host disease (GVHD) and may compromise transplant outcome. We have compared the outcome of matched and mismatched transplants from unrelated donors in 137 children with acute lymphoblastic leukemia (ALL). Their disease status was complete remission (CR)-1, 24 patients; CR-2, 88 patients; CR-3, 18 patients; CR-4, 2 patients ; and relapse, 5 patients. CAMPATH monoclonal antibodies were used for T-ce ll depletion and cyclosporin A was given to 134 children together with shor t-course methotrexate in 43, mainly when there was HLA disparity. Fifty-two donor/recipient pairs were HLA-mismatched, 41 at HLA-A and -B and 11 at HL A-DR and -DQ loci. Overall graft failure was increased in recipients of mar row mismatched at either HLA-A, -B, -DR, or -DQ (15.7% v 4.8%; P = .057) ma inly because there was a higher proportion of children with primary graft f ailure (11.8% v 1.2%; P = .012). The presence of an HLA-C locus mismatch di d not independently increase the likelihood of graft failure. There was no significant difference in the incidence of acute GVHD greater than or equal to grade 2 between the matched and mismatched groups (P = .849). For patie nts in CR-2, the risk of relapse post-BMT was significantly lower if leukem ic relapse occurred off-treatment (P = .005). The Kaplan-Meier overall and leukemia-free survival (LFS) estimates for recipients of matched and mismat ched BMT, respectively, at 36 months were 49% versus 42% (P = .380) and 45% versus 40% (P = .654). Although HLA mismatching results in an increased oc currence of primary graft failure with T-cell-depleted allografts, it allow s more donors to be identified rapidly for children with ALL without compro mising overall transplant outcome. (C) 1999 by The American Society of Hema tology.