Current status of therapeutic approaches to adult T-cell leukemia.

More than 2 decades have elapsed since the proposal of adult T-cell leukemia (ATL). Since then, the discovery of the etiologic virus, human T-cell leukemia virus type I (HTLV-I), and the establishment of the diagnostic steps of serum test and molecular study have clearly defined ATL as a distinct disease entity. Because conventional chemotherapy, which is active against other lymphoid malignancies, was proven to be ineffective for treating aggressive forms of ATL, ATL has become the target of several clinical studies for the purpose of improving therapeutic outcomes. Combination chemotherapy exclusively designed for ATL has considerably elevated the treatment response rate in ATL patients, but it has not sufficiently extended the median survival time. The introduction of antiviral agents has led to surprising effects for patients with acute ATL. Monoclonal antibodies seem to be promising, especially for patients with chemotherapy-resistant disease. Unfortunately, these approaches did not prove to be sufficient for most patients with ATL to obtain long-term survival. Recent promising reports on allogeneic stem cell transplantation (allo-SCT) for ATL have suggested that allo-SCT could overcome the limitations that other treatment modalities have not surmounted. More efforts are clearly needed to clarify the usefulness of allo-SCT, especially with reduced-intensity conditioning regimens, for ATL patients.