Bone marrow transplantation for chronic myeloid leukaemia: The effects of differing criteria for defining chronic phase on probabilities of survival and relapse

We studied actuarial survival and relapse in 251 patients with chronic myeloid leukaemia (CML) treated by bone marrow transplantation (BMT) from HLA-identical sibling donors at a single institution. According to the institutional criteria used to define disease phase at the time of BMT, the 5-year probabilities of survival were 58.1% (95% confidence internal 50-66%) for 205 chronic-phase patients and 21.5% (95%CI 12-37%) for 46 advanced-phase patients (P<0.00001); the corresponding values for relapse were 34.8% (95%CI 27-44%) versus 72.7% (95%CI46-89%). When disease phase was defined strictly according to the criteria of the International Bone Marrow Transplant Registry, the survival for 154 chronic-phase patients increased to 60.1% (95%CI 51-69%) and that for 97 advanced-phase patients increased to 37.6% (95%CI 28-48%). There was a parallel change in probabilities of relapse in the two patient groups (33.9% [95%CI 25-44%] and 51.3% [95%CI 37-66%], respectively). We also observed that patients transplanted in advanced phase had a higher incidence of grades III-TV acute graft-versus-host disease (P=0.001) and transplant-related mortality (P=0.02) than those undergoing BMT for chronic-phase disease. We recommend that transplant centres reporting results of BMT should always specify the precise criteria used for defining disease phase in order to ensure that results between different centres are strictly comparable.