IDENTICAL-TWIN BONE-MARROW TRANSPLANTS FOR LEUKEMIA

Objective: To compare outcomes of identical-twin with HLA-identical si bling bone marrow transplants for leukemia. Design: Matched-pair analy sis comparing relapse, treatment-related mortality, and leukemia-free survival in cohorts matched for disease and variables correlated with transplant outcome, with and without adjustment for graft-versus-host disease. Setting: 163 institutions worldwide between 1978 and 1990, re porting to the International Bone Marrow Transplant Registry. Particip ants: 103 identical-twin transplants: 24 for acute lymphoblastic leuke mia (ALL) in first remission, 45 for acute myelogenous leukemia (AML) in first remission, and 34 for chronic myelogenous leukemia (CML) in f irst chronic phase. Results were compared with those in 1030 concurren t HLA-identical sibling transplants matched for prognostic factors. Re sults: Three-year probabilities of relapse after identical-twin compar ed with HLA-identical sibling transplants were as follows: ALL, 36% (9 5% CI, 17% to 55%) compared with 26% (CI, 20% to 32%); AML, 52% (CI, 3 7% to 67%) compared with 16% (CI, 12% to 20%); and CML, 40% (CI, 23% t o 57%) compared with 7% (CI, 4% to 10%). Increased relapse risks in AM L and CML persisted after adjusting for graft-versus-host disease (rel ative risk, 3.1 [CI, 1.9 to 5.1] and 5.5 [CI, 2.8 to 11.0], respective ly). Although twins had less treatment-related mortality than HLA-iden tical siblings, leukemia-free survival was similar. Three-year leukemi a-free survival probabilities after twin compared with HLA-identical s ibling transplants were as follows: ALL, 57% (CI, 37% to 77%) compared with 58% (CI, 52% to 64%); AML, 42% (CI, 27% to 57%) compared with 55 % (CI, 50% to 60%); and CML, 59% (CI, 42% to 76%) compared with 61% (C I, 56% to 66%). Conclusions: Identical-twin transplants in AML and CML are associated with increased relapse risk compared with HLA-identica l sibling transplants. A similar trend was observed in ALL but was not statistically significant. Increased relapse in twin transplants is n ot explained by lack of graft-versus-host disease. Leukemia-free survi val after twin and HLA-identical sibling transplants is similar becaus e increased relapse in twins is offset by decreased treatment-related mortality.