Hydroxyurea plus low-dose aspirin is the most appropriate treatment for patients with essential thrombocythemia (ET) in whom treatment is indicated. Treatment of ET requires reduction of the platelet count; however, when and whom to treat remain controversial. Although the exact platelet count does not determine the risk for thrombosis, lowering the platelet count in patients at risk for thrombosis will decrease this risk and, possibly, the risk for secondary myelofibrosis. Patients do not require treatment if they are younger than 60 years, have a platelet count less than 1 million/µL (1000 × 109/L), and have no history of thrombosis. Hydroxyurea plus low-dose aspirin is the best treatment option for ET when treatment is required in patients older than 60 years, those with a platelet count greater than 1 million/µL (1000 × 109/L), or those with a history of thrombosis or an increased risk for thrombosis because of cardiovascular risk factors such as hypertension and diabetes mellitus. Hydroxyurea plus low-dose aspirin reduces the risk for arterial thrombosis and bleeding (regardless of the platelet count achieved) in patients with ET.
Anagrelide is another platelet-lowering agent used to manage ET, but in a randomized trial comparing anagrelide with hydroxyurea, anagrelide was found to have a less favorable side effect profile. Likewise, hydroxyurea, but not anagrelide, decreases thrombotic risk independent of platelet-count lowering.
Ruxolitinib is an inhibitor of constitutively active JAK2 V617F. Although 50% of patients with ET demonstrate this mutation, ruxolitinib has a therapeutic role only in alleviating the splenomegaly and systemic symptoms of primary myelofibrosis.
Warfarin has not been studied for primary prophylaxis of ET; therefore, it would not be an appropriate treatment choice for this patient.
The patient's age is an important factor in initiating therapy, making observation an inappropriate choice.