All patients should be phlebotomized to keep the hematocrit <= 45 percent.
All patients should be considered for aspirin prophylaxis (or other antiplatelet agent if aspirin cannot be tolerated).
• A patient with a history of thrombotic episode is at high risk for further thrombotic events and so needs to be more aggressively treated.
• A person > 70 years may benefit from low dose aspirin therapy for prophylaxis.
Further therapy depends on:
(1) age
(2) evidence of high risk disease (presentation with thrombosis OR high rate of phlebotomy OR platelet count > 400,000 per µL)
(3) concern about secondary leukemias and cancer related to use of phosphorus-32 and agents like chlorambucil.
If the patient is > 70, then the patient may receive myelosuppressive therapy (with phosphorus-32 or busulfan).
If the patient has high risk disease and from 40-70 years of age, then the patient may receive myelosuppression (with hydroxyurea).
If the patient has high risk disease and < 40 years of age, then consider therapy with interferon alpha or anagrelide (an agent that reduces platelet production and aggregation).
If the patient is <= 70 and not in high risk group, then the choice may be to not give myelosuppression initially, but to reconsider if complications occur.
