Adult T-cell leukemia/lymphoma (ATLL) develops in elderly individuals who have been infected with human T-cell leukemia virus type 1 (HTLV-1), and the prognosis for patients with ATLL has been extremely poor. Retrospective studies of allogeneic stem cell transplantation (alloSCT) for selected populations of patients have achieved several encouraging results; however, the reported incidence of transplantation-related mortality (TRM) have been high, even though more than 80% of patients received stem cells from related donors and the patients were relatively young for ATLL. This report documents a prospective feasibility study of alloSCT with reduced-intensity conditioning (RIST) for elderly ATLL patients (>50 years). Regimen-related toxicities and nonhematologic toxicities were acceptable. Fourteen of 15 evaluable patients achieved complete donor chimerism within 90 days, and 1 patient had early TRM after RIST. The HTLV-1 proviral load became undetectable in 8 of 15 patients, suggesting that RIST has potential as an antiviral treatment. The results of alloSCT are promising, and 30% to 40% of patients who achieve remission and have suitable donors can now become long-term survivors with either conventional alloSCT or RIST. It is clear that a graft-versus-ATLL effect is present after alloSCT, regardless of the conditioning regimen or the stem cell source.
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