Management of Thrombocytosis with Aspirin

Introduction to Aspirin Therapy in Essential Thrombocythemia

The National Comprehensive Cancer Network recommends aspirin (81-100 mg daily) for low-risk patients with essential thrombocythemia (ET) who have a JAK2 mutation or cardiovascular risk factors, and for all patients with microvascular symptoms 1, 2

For very low-risk ET patients (age ≤60 years, no JAK2 mutation, no prior thrombosis), observation without aspirin is appropriate, with monitoring for new thrombosis, acquired von Willebrand disease, or disease-related bleeding 1
Low-risk ET patients (age ≤60 years, with JAK2 mutation, no prior thrombosis) should receive aspirin 81-100 mg daily, as the JAK2 mutation increases thrombotic risk even in younger patients without prior events 1, 2
High-risk ET patients (age >60 years and/or prior thrombosis) should receive aspirin 81-100 mg daily plus cytoreductive therapy (hydroxyurea as first-line), targeting a platelet count <400 × 10⁹/L 1, 2

Aspirin is the treatment of choice for microvascular occlusive symptoms (erythromelalgia, transient neurologic symptoms, headaches, chest pain) regardless of platelet count in the typical ET range 1, 2
In cases of extreme thrombocytosis (platelets >1,000 × 10⁹/L), rule out acquired von Willebrand syndrome (AvWS) with ristocetin cofactor and multimer analysis before starting aspirin, and use aspirin with extreme caution or avoid it if AvWS is present 1, 3

Obtain a careful bleeding history before starting aspirin, and monitor for petechiae, ecchymosis, epistaxis, or gastrointestinal bleeding, as the absolute bleeding risk with aspirin ranges from 1-2 major events per 1,000 patient-years 1, 4
Regular complete blood count monitoring is essential to track platelet trends and assess for progression 2