Reduced risk of recurrent leukaemia in bone marrow transplant recipients after cytomegalovirus infection.

The first 72 consecutive bone-marrow transplant recipients with haematological malignancies (29 with acute nonlymphoblastic leukaemia, 31 with acute lymphoblastic leukaemia, nine with CML and three with myelofibrosis, IgA myeloma and T-cell lymphoma, respectively) were investigated for the frequency of relapses 1 year or later after bone-marrow transplantation. Seven relapses occurred from 30 to 850 d after transplantation (median 180 d). All relapses occurred in patients with acute leukaemia less than or equal to 18 years of age with a high risk for relapse, i.e. transplanted in second or later remission or with more than 10% blasts in the marrow before transplantation. Among all patients the probability of relapse was increased in patients without cytomegalovirus (CMV) infection (P = 0.001) and in patients without chronic GVHD (P = 0.049). Among leukaemic patients less than or equal to 18 years of age with a high risk of relapse all relapses occurred in patients (n = 11) without CMV infection, whereas no relapses were seen in patients (n = 13) with CMV infection (P = 0.006). Known risk factors for leukaemic relapse were comparable in both groups.