Is there a graft-versus-leukaemia effect in the absence of graft-versus-host disease in patients undergoing bone marrow transplantation for acute leukaemia?

During a 13-year period, 5200 autografts, 1039 HLA-identical sibling transplants without acute or chronic graft-vs.-host disease (GVHD) and 67 twins were reported to the European Group for Blood and Marrow Transplantation EBMT. Follow-up time was a median of 32 months. Diagnoses were acute myeloid leukaemia (AML, 4521) and acute lymphoblastic leukaemia (ALL, 1785) in first complete remission. The probability of relapse at 5 years was 51 +/- 1% in the autografts, 45 +/- 8% in the twins and 34 +/- 2% among the HLA-identical siblings (auto vs. sibs, P < 0.0001). In multivariate analyses, the following factors were significantly associated with an increased risk of relapse: ALL vs. AML M3 [relapse rate (RR) 2.29, P < 0.0001], AML non-M3 vs. AML M3 (RR 1.8, P < 0.0001), autograft vs. sibling transplant (RR 1.76, P < 0.0001), interval diagnosis to transplantation < 261 d (RR 1.45, P < 0.001) and other conditioning vs. total body irradiation (RR 1.16, P = 0.001). Transplant-related mortality was the same in the three groups at approximately 10% at 2 years. Five-year leukaemia-free survival was 42 +/- 1% in the autografts, 44 +/- 8% in the twins and 58 +/- 2% among the siblings (auto vs. sibs, P < 0.0001). The factors significant for relapse were also significant in multivariate analyses for leukaemia-free survival. In addition, children had a significantly better leukaemia-free survival than adults (RR 0.82, P < 0.0001). Recipients of bone marrow from HLA-identical siblings without GVHD had a lower risk of relapse and a better leukaemia-free survival than recipients of autografts. This may be as a result of a graft-vs.-leukaemia effect in the absence of GVHD.