Risk-adapted therapy in essential thrombocythemia and polycythemia vera.

The clinical course of Polycythemia vera (PV) and Essential Thrombocythemia (ET) is marked by an high incidence of thrombotic complications, which represent the main cause of morbidity and mortality. Major predictors of vascular events are increasing age and previous thrombosis. Myelosuppressive drugs can reduce the rate of thrombosis, but there is concern that their use raises the risk of PV and ET transformation into acute leukemia. To tackle this dilemma, a risk-oriented management strategy is recommended. Low-risk patients with PV should be treated with phlebotomy and low-dose aspirin, whereas those with ET can be left untreated. Cytotoxic therapy is indicate in high-risk patients and the drug of choice is hydroxyurea because its leukemogenicity is low, if any. New therapeutic options, theoretically devoid of leukemic risk, such as alpha-interferon, anagrelide and imatinib should be reserved to selected patients and require further clinical experience.