Therapeutic options for essential thrombocythemia and polycythemia vera.

Several options exist for treating essential thrombocythemia and polycythemia vera. One approach is to assign the patient to a risk category from which treatment recommendations follow. The principal risks of essential thrombocythemia include thrombosis, major hemorrhage, and conversion to leukemia or myelofibrosis. Risk factors for thrombosis include age and prior thrombosis. Smoking and obesity have been implicated in isolated series. High-risk patients with essential thrombocythemia can be defined as those 60 years of age or older or those who have had a thrombosis at any age. These patients should be treated with hydroxyurea. If hydroxyurea cannot be tolerated, anagrelide and interferon-alpha (IFN-alpha) are alternatives. Low-dose aspirin (40 to 325 mg) can be used for patients whose platelet counts are < 1,500 x10(9)/L. Low-risk patients are those less than 60 years old who have not had thrombosis, who have no cardiovascular risk factors, and whose platelet counts are < 1,500 x 10(9)/L. These patients can be observed or placed on low-dose aspirin. Intermediate-risk patients are those less than 60 years who have not had thromboses, but who have platelet counts > 1,500 x 10(9)/L or who have significant cardiovascular risk factors. These patients should have their risk factors treated and may be given low-dose aspirin if the platelet count is < 1,500 x 10(9)/L. They can be observed or treated with anagrelide, hydroxyurea, or IFN-alpha. The Mayo Clinic experience suggests that no specific treatment affects outcomes of pregnancies. In high-risk pregnant women who need treatment, IFN-alpha is used. The principal risks of polycythemia vera are thrombosis, postpolycythemia myeloid metaplasia, and acute leukemia. Risk factors for thrombosis include age, the use of phlebotomies, the rate of phlebotomies, and a prior history of thrombosis. Platelet counts have not been definitively linked to an increased risk of thrombosis. High-risk polycythemia vera patients are those 60 years of age or older (some groups use 70 years) or those of any age who have had thrombosis. They should be treated with phlebotomy and hydroxyurea or IFN-alpha. Selected patients may be treated with anagrelide. A typical target range for phlebotomy is a hematocrit of < 42% for women and < 45% for men. Low-dose aspirin can be used if the platelet count is < 1,500 x 10(9)/L. Low-risk patients are those less than 60 years old who have had no thrombosis, no cardiovascular risk factors, and whose platelets are < 1,500 x 10(9)/L. These patients can be managed with phlebotomy alone or phlebotomy and low-dose aspirin. Intermediate-risk patients are those who are less than 60 years old, who have not had thrombosis, but who have platelet counts > 1,500 x 10(9)/L or who have cardiovascular risk factors. The cardiovascular risk factors should be treated, along with phlebotomy alone or with IFN-alpha. Low-dose aspirin is reasonable for those with platelet counts < 1,500 x 10(9)/mL. Anagrelide can be used with phlebotomy in selected patients. Women of childbearing age who are in the low-risk or intermediate-risk group can be treated with phlebotomy alone and low-dose aspirin if the platelet count is < 1,500 x 10(9)/L. For high-risk patients or pregnant patients, IFN-alpha can be added.