Management of essential thrombocythemia.

Essential thrombocythemia (ET) is a Philadelphia chromosome (Ph)-negative myeloproliferative neoplasm (MPN) characterized by thrombocytosis and megakaryocytic hyperplasia of the bone marrow, with presence of the JAK2 V617F mutation in 50%-60% of patients. ET evolves to myelofibrosis in a minority of cases, whereas transformation to acute leukemia is rare and increases in association with the use of certain therapies. Survival of ET patients does not substantially differ from that of the general population. However, important morbidity is derived from vascular complications, including thrombosis, microvascular disturbances, and bleeding. Because of this, treatment of ET must be aimed at preventing thrombosis and bleeding without increasing the risk of transformation of the disease. Patients are considered at high risk of thrombosis if they are older than 60 years or have a previous history of thrombosis and at high risk of bleeding if platelet counts are > 1500 × 10(9)/L. Patients with low-risk ET are usually managed with low-dose aspirin, whereas treatment of high-risk ET is based on the use of cytoreductive therapy, with hydroxyurea as the drug of choice and IFN-α being reserved for young patients or pregnant women. For patients resistant or intolerant to hydroxyurea, anagrelide is recommended as second-line therapy. Strict control of coexistent cardiovascular risk factors is mandatory for all patients. The role in ET therapy of new drugs such as pegylated IFN or the JAK2 inhibitors is currently under investigation.