Evaluation of two prognostic indices for adult T‐cell leukemia/lymphoma in the subtropical endemic area, Okinawa, Japan

Aggressive adult T‐cell leukemia/lymphoma (ATL) has an extremely poor prognosis and is hyperendemic in Okinawa, Japan. This study evaluated two prognostic indices (PIs) for aggressive ATL, the ATL‐PI and Japan Clinical Oncology Group (JCOG)‐PI, in a cohort from Okinawa. The PIs were originally developed using two different Japanese cohorts that included few patients from Okinawa. The endpoint was overall survival (OS). Multivariable Cox regression analyses in the cohort of 433 patients revealed that all seven factors for calculating each PI were statistically significant prognostic predictors. Three‐year OS rates for ATL‐PI were 35.9% (low‐risk, n = 66), 10.4% (intermediate‐risk, n = 256), and 1.6% (high‐risk, n = 111), and those for JCOG‐PI were 22.4% (moderate‐risk, n = 176) and 5.3% (high‐risk, n = 257). The JCOG‐PI moderate‐risk group included both the ATL‐PI low‐ and intermediate‐risk groups. ATL‐PI more clearly identified the low‐risk patient subgroup than JCOG‐PI. To evaluate the external validity of the two PIs, we also assessed prognostic discriminability among 159 patients who loosely met the eligibility criteria of a previous clinical trial. Three‐year OS rates for ATL‐PI were 34.5% (low‐risk, n = 42), 9.2% (intermediate‐risk, n = 109), and 12.5% (high‐risk, n = 8). Those for JCOG‐PI were 22.4% (moderate‐risk, n = 95) and 7.6% (high‐risk, n = 64). The low‐risk ATL‐PI group had a better prognosis than the JCOG‐PI moderate‐risk group, suggesting that ATL‐PI would be more useful than JCOG‐PI for establishing and examining novel treatment strategies for ATL patients with a better prognosis. In addition, strongyloidiasis, previously suggested to be associated with ATL‐related deaths in Okinawa, was not a prognostic factor in this study.