From the Guidelines
Aspirin therapy is recommended for patients with essential thrombocythemia (ET) who have vascular symptoms or are at low-risk, with a dose of 81-100 mg daily. The primary criteria for adding aspirin in ET include vascular symptoms or low-risk disease, as defined by the presence of a JAK2 mutation and no prior history of thrombosis 1. According to the NCCN guidelines, aspirin can be considered to reduce the risk of thrombotic complications for patients with very low-risk, low-risk, or intermediate-risk ET 1.
Key Considerations
- Aspirin should be used with caution in patients with acquired von Willebrand disease (VWD) who have an increased risk of bleeding 1.
- The risk and benefits of higher-dose aspirin must be weighed based on the presence of vasomotor symptoms and the risk of bleeding; it may be appropriate in carefully selected patients, as clinically indicated 1.
- Platelet counts should ideally be below 1,500 × 10^9/L to minimize bleeding risk, although this is not a strict criterion for aspirin use 1.
- Aspirin works by irreversibly inhibiting platelet cyclooxygenase-1, reducing thromboxane A2 production and preventing platelet aggregation, which helps prevent arterial thrombotic complications commonly seen in ET patients.
Special Populations
- Patients with CALR-mutated ET may not benefit from low-dose aspirin, but there is not enough evidence to recommend withholding aspirin for this group of patients 1.
- Patients with very high platelet counts (>1,500 × 10^9/L) should be cautious when using aspirin due to increased bleeding risk from acquired von Willebrand syndrome, history of significant bleeding, or aspirin allergy.
From the Research
Criteria for Adding Aspirin in Essential Thrombocythemia (ET)
The decision to add aspirin in ET is based on several factors, including:
- Thrombosis risk: Aspirin is recommended for patients with a high risk of thrombosis, such as those with a history of thrombosis, age older than 60 years, or a JAK2 gene variant 2.
- Platelet count: Aspirin is contraindicated in ET patients with a very high platelet count (> 1500 x 10(9)/L) leading to the acquisition of von Willebrand factor deficiency 3.
- Bleeding risk: Aspirin may unmask a latent bleeding diathesis frequently present in ET, which may result in severe hemorrhagic complications 3.
- Individual risk factors: Patients with ET may be treated with low-dose aspirin, either alone or in combination with a cytoreductive drug such as hydroxyurea, based on individual risk factors for thrombosis 2.
Aspirin Dosage and Formulation
The recommended dosage of aspirin in ET is:
- Low-dose aspirin (81-100 mg) once daily, which irreversibly inhibits platelet thromboxane A2 (TxA2) production by acetylating cyclo-oxygenase-1 4.
- Plain aspirin is preferred over enteric coated aspirin because some ET patients display poor responsiveness ("resistance") to the latter 4.
- Twice daily aspirin administration may be considered to overcome the problem of inadequate inhibition of platelet TxA2 production, but additional data on gastrointestinal tolerability are needed 4, 5.
Risk Stratification
Patients with ET can be stratified into different risk categories, including:
- Very low risk: Patients with a low platelet count, no history of thrombosis, and no JAK2 mutation may not require aspirin therapy 5, 6.
- Low risk: Patients with a low platelet count, no history of thrombosis, and a JAK2 mutation may be treated with aspirin 5.
- High risk: Patients with a history of thrombosis, age older than 60 years, or a JAK2 mutation should be treated with aspirin and cytoreductive therapy 2, 5.