Allogeneic hematopoietic stem cell transplantation (HSCT) is an effective treatment for adult T cell leukemia/lymphoma (ATLL), but shows high mortality. We evaluated the feasibility of reduced-intensity transplantation using fludarabine and busulfan, with particular focus on the clinical impact of antithymocyte globulin (ATG) in the conditioning regimen. Fourteen elderly patients with aggressive ATLL were enrolled in the current study without ATG, and were compared to those in 15 patients who were treated similarly, but with ATG, in our previous study. Engraftment was prompt, and treatment was tolerable. Overall (OS) and progression-free survival (PFS) at 3 years were 36% and 31%, respectively. HTVL-1 proviral load became undetectable by the polymerase chain reaction in 62% of patients. Compared to the previous study with ATG, complete donor chimera was significantly delayed. Although early relapse tended to be decreased, OS or PFS was not improved significantly. Analysis of combined data from both our current and previous studies disclosed that grade I-II acute GVHD was the only factor that favorably affected OS and PFS. These data suggested the presence of a graft-versus-ATLL effect and the feasibility of a transplant procedure without ATG in elderly ATLL patients, but could not demonstrate the clinical benefit of incorporating ATG.
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