Approach of Schafer for Management of Primary (Clonal) Thrombocythemia

 

Patient selection: A patient with a primary (clonal) thrombocytosis and platelet count > 450,000 per µL.

 

Parameters:

(1) symptomatic status

(2) platelet count

(3) age

(4) cardiovascular risk factors

(5) history (thrombosis, bleeding)

(6) thrombosis present

(7) active ischemia (cerebrovascular, digital, other)

 

Rule	Management
symptomatic with active ischemia	immediate cytoreduction (consider plateletpheresis); antiplatelet therapy
symptomatic with history of bleeding or thrombosis, thrombosis present	cytoreduction; antiplatelet therapy
symptomatic with history of bleeding or thrombosis	cytoreduction
asymptomatic but at high risk (age > 60 years or cardiovascular risk factors)	cytoreduction; antiplatelet therapy
asymptomatic with history of bleeding or thrombosis	cytoreduction
asymptomatic with platelet count > 1.5 million per µL	cytoreduction
asymptomatic not at high risk with platelet count <= 1.5 million per µL	follow without therapy

 

where:

• The rules are not hard and fast. For example, I would imagine that cytoreduction might be done at a lower platelet count, especially if it was rising sharply.

• A symptomatic person with active (not just history of) bleeding would be treated with cytoreduction but I am not sure about the use of aspirin (see below).

• Cytoreduction for asymptomatic history of bleeding or thrombosis is not shown in Figure 3, but is indicated as a risk factor in the text on page 1215.

 

Cytoreduction is usually achieved by therapy with

(1) hydroxyurea

(2) anagrelide

(3) interferon alpha (may have intolerable side effects). This is the treatment of choice for a younger woman who may become pregnant (hydroxyurea is teratogenic; anagrelide is not known to be safe)

(4) alkylating agents in an older patient who cannot tolerate other therapy (use in younger patients is avoided due to risk of acute leukemia)

 

The preferred antiplatelet therapy would be aspirin but other agents may be required if a patient cannot tolerate aspirin. Low doses of aspirin are often effective without increasing the risk of excessive bleeding.