Long-term follow-up of 386 consecutive patients with essential thrombocythemia: safety of cytoreductive therapy

Cytotoxic agents like Hydroxyurea, Busulfan and Interferon-alpha are to date the most commonly used therapeutic approaches in Essential Thrombocythemia (ET). However, few data on the efficacy and safety of these agents in the long-term are currently available. We report a retrospective analysis of the long-term outcome of 386 consecutive ET patients, followed at single Institution for a median follow-up of 9.5 years (range, 3-28.5). Cytoreductive therapy was administered to 338 patients (88%), obtaining a response in 86% of cases. Forty-five patients (12%) experienced a thrombosis. Among baseline characteristics, only history of vascular events prior to ET diagnosis predicted a higher incidence of thrombosis. Evolution in acute leukemia/myelofibrosis occurred in 6 (1,5%) and 20 (5%) patients, and was significantly higher in patients receiving sequential cytotoxic agents. Overall survival was 38% at 19 years and was poorer for patients older than 60 years, with higher leukocytes count (>15 x 10(9)/L), hypertension and mellitus diabetes at ET diagnosis and for patients experiencing a thrombotic event during follow-up. Cytoreductive therapy was effective in decreasing platelet number with negligible toxicity; however, thrombocytosis control did not reduce the incidence of thrombosis and, for patients who received sequential therapies, the probability of disease evolution was higher and survival was poorer. Am. J. Hematol. 84:215-220, 2009. (C) 2008 Wiley-Liss, Inc.