Bone marrow transplantation for chronic myeloid leukaemia in first chronic phase: importance of a graft-versus-leukaemia effect.

We analysed the incidence of graft failure, graft-versus-host disease (GVHD) and relapse of leukaemia in 208 patients undergoing allogeneic bone marrow transplantation (BMT) for chronic myeloid leukaemia in chronic phase in eight transplant centres in Europe and the United States. 106 patients received unmanipulated donor bone marrow (Group 1) and 102 patients received marrow depleted of T-cells by incubation with the monoclonal antibodies Campath-1 or CT-2 and complement (Group 2). The incidence of graft failure was higher and of GVHD was lower in Group 2 than in Group 1. Relapse of leukaemia occurred more frequently in patients in Group 2 than in Group 1 (17 v. 2, P less than 0.001). Multivariate analysis showed that the following factors were associated with an increased risk of relapse: the use of T-cell depletion, the absence of GVHD and a high platelet count at the time of admission for transplant. The findings support the concept that a graft-versus-leukaemia effect mediated by T-lymphocytes is important for cure of leukaemia after BMT.