Watchful waiting (WW) is among the treatment options indicated for patients with indolent adult T-cell leukemia-lymphoma (ATL). However, we previously showed that the long-term prognosis of patients with smoldering and chronic ATL is often worse than expected, with many undergoing transformation to aggressive ATL. To identify clinical features associated with transformation of smoldering/chronic ATL, we retrospectively analyzed the clinical features of 44 patients (14 smoldering and 30 chronic) who experienced transformation during WW. An elevated lactate dehydrogenase (LDH) value was most often observed (n = 30) at the time of transformation, especially in the chronic type (n = 24). Major organ involvement, lymphadenopathy, and hypercalcemia were shown to be associated with transformation in transformed patients without elevated LDH. The median overall survival time after transformation was only 7.8 months, and the prognosis was poor after transformation in those fulfilling the criteria of acute type, similar to that of de novo aggressive ATL. Laboratory data, such as LDH, and clinical signs including exacerbation of performance status, skin lesions, and lymphadenopathy should all be monitored during WW to ensure appropriate timing of chemotherapy initiation. Identification of optimal predictive markers for transformation and new therapeutic options is warranted to improve outcomes in indolent ATL.
Keywords: Adult T-cell leukemia–lymphoma (ATL); Chronic; Smoldering; Transformation.