A NEW CLASSIFICATION OF CLINICAL STAGES OF ADULT T-CELL LEUKEMIA BASED ON PROGNOSIS OF THE DISEASE

Adult T-cell leukemia (ATL) has been classified into three clinical su btypes: acute, chronic, and smoldering type. However, these clinical s ubtypes of ATL do not always correlate with prognosis. We propose a ne w criterion for classification of clinical stages of ATL, based on the expression of Ki-67 antigen in peripheral blood T lymphocytes. We ana lyzed Ki-67 antigen expression in 45 ATL patients, classified as 18 ac ute, 17 chronic, and ten smoldering type. We found that in 23 patients with more than 18% Ki 67 antigen-positive T cells, the disease progre ssed very aggressively, and all patients died within 1 year (mean surv ival, 105 days). This group included 15 of 16 patients classified as ' acute', seven of 15 patients classified as 'chronic', and one of nine patients classified as 'smoldering' type. In contrast, 15 out of 17 pa tients with less than 18% Ki-67 antigen-positive T cells were still al ive at the end of the study, with a mean survival of 750 days. Only tw o patients died in this group, and after a very long survival (599 and 978 days, respectively). We therefore propose the following new class ification for ATL: (i) Aggressive ATL; percentage of Ki-67 antigen-pos itive cells more than 18% in peripheral blood T lymphocytes. (ii) Stab le ATL; percentage less than 18%. This classification strongly correla tes with the prognosis of patients with ATL.