What distinguishes high-risk from low-risk patients with Essential Thrombocythemia (ET) for myocardial infarction (heart attack) or cerebrovascular accident (stroke)?

From the Guidelines

High-risk patients with Essential Thrombocythemia (ET) can be distinguished from low-risk patients based on factors such as age ≥60 years, prior thrombosis, cardiovascular risk factors, and the presence of JAK2 V617F mutation, as outlined in the International Prognostic Score for ET (IPSET) and its modified version, IPSET-Thrombosis 1. The IPSET-Thrombosis model stratifies patients into three risk categories: low risk, intermediate risk, and high risk, with significantly different thrombosis-free survival rates, ranging from 87% after 15 years of follow-up for low-risk patients to 50% after 7-year follow-up for high-risk patients. Some key factors that contribute to the distinction between high-risk and low-risk patients include:

• Age ≥60 years
• Prior thrombosis
• Cardiovascular risk factors such as hypertension, diabetes, and smoking
• Presence of JAK2 V617F mutation
• Leukocytosis, with a leukocyte count ≥11 x 10^9/L The presence of these factors can significantly increase the risk of thrombotic events, including myocardial infarction and cerebrovascular accident, and guide treatment decisions, such as the use of cytoreductive therapy and low-dose aspirin in high-risk patients 1. It is essential to note that the risk stratification models, including IPSET-Thrombosis, have limited applicability in determining pregnancy complications, and a careful obstetric history and multi-disciplinary team approach are crucial in managing pregnant women with ET 1. Regular reassessment of risk factors is vital, as a patient's risk category may change over time with age or the development of new comorbidities, and treatment strategies should be adapted accordingly to minimize the risk of thrombotic events and improve quality of life.

From the Research

Risk Factors for Thrombosis in Essential Thrombocythemia (ET)

The following factors distinguish high-risk from low-risk patients with Essential Thrombocythemia (ET) for myocardial infarction (heart attack) or cerebrovascular accident (stroke):

• Age: patients older than 60 years are considered high-risk 2, 3
• Prior thrombosis: patients with a history of thrombosis are considered high-risk 2, 4, 3
• Platelet count: patients with platelet counts > 1,500 x 10(9)/L are considered high-risk 2, 4, 3
• Cardiovascular risk factors: patients with significant cardiovascular risk factors, such as smoking and obesity, are considered high-risk 2
• Presence of vascular disease: patients with presence of vascular disease, such as arteriosclerosis, are considered high-risk 4

Treatment Recommendations

Treatment recommendations for high-risk and low-risk ET patients are as follows:

• High-risk patients: cytoreductive therapy with hydroxyurea as the drug of choice, and IFN-α being reserved for young patients or pregnant women 2, 3
• Low-risk patients: low-dose aspirin, with cytoreductive therapy considered for patients with significant cardiovascular risk factors or platelet counts > 1,500 x 10(9)/L 2, 4, 3
• Intermediate-risk patients: treatment with anagrelide, hydroxyurea, or IFN-α, with strict control of coexistent cardiovascular risk factors 2, 3

Platelet-Leukocyte Interactions

Platelet-leukocyte interactions may contribute to the pathogenesis of thrombosis in ET, and low-dose aspirin has been shown to reduce platelet-leukocyte conjugates in low-risk ET patients 5