Cyclophosphamide (Cy) in combination with busulfan (Bu) or total body irradiation (TBI) is the most commonly used myeloablative conditioning regimen in patients with chronic myeloid leukemia (CML). We used data from the Center for International Bone Marrow Transplantation Research to compare outcomes in adults who underwent hematopoietic cell transplantation for CML in first chronic phase after myeloablative conditioning with Cy in combination with TBI, oral Bu, or intravenous (i.v.) Bu. Four hundred thirty-eight adults received human leukocyte antigen (HLA)-matched sibling grafts and 235 received well-matched grafts from unrelated donors (URD) from 2000 through 2006. Important differences existed between the groups in distribution of donor relation, exposure to tyrosine kinase inhibitors, and year of transplantation. In multivariate analysis, relapse occurred less frequently among patients receiving i.v. Bu compared with TBI (relative risk [RR], .36; P=022) or oral Bu (RR, .39; P=028), but nonrelapse mortality and survival were similar. A significant interaction was detected between donor relation and the main effect in leukemia-free survival (LFS). Among recipients of HLA-identical sibling grafts, but not URD grafts, LFS was better in patients receiving i.v. Bu (RR, .53; P=025) or oral Bu (RR, .64; P=017) compared with TBI. In CML in first chronic phase, Cy in combination with i.v. Bu was associated with less relapse than TBI or oral Bu. LFS was better after i.v. or oral Bu compared with TBI.
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