Evidence and expertise in the management of polycythemia vera and essential thrombocythemia.

Major causes of morbidity and mortality in polycythemia vera (PV) and essential thrombocythemia (ET) are represented by thrombosis and bleeding, progression to myelofibrosis and transformation to acute leukemia. Myelosuppressive therapy, preferentially with hydroxyurea, can reduce the rate of vascular complications, but there is some concern about an increased rate of leukemic transformation with this agent. Therefore, management of these disorders poses a significant challenge, and a risk-oriented therapeutic approach should be strictly followed to avoid inappropriate exposure to cytotoxic drugs on one side or suboptimal treatment on the other. Established risk factors for cardiovascular events are represented by older age and previous thrombosis, whereas impact of novel biological factors, including leukocytosis and JAK2V617F mutational status and/or mutational burden, is under active investigation. Low-risk PV patients should be managed only with phlebotomy and aspirin, whereas high-risk patients should also receive cytotoxic therapy. Regarding the management of ET, there is no clear indication for intervention in low-risk patients, whereas high-risk patients should be managed with chemotherapy. Other therapeutic options, such as interferon-alpha or anagrelide, may find place in selected patients including those who are resistant/intolerant to hydroxyurea. Finally, there is great expectation for novel drugs targeting the constitutively active JAK2/STAT pathway.