Risk of Thromboembolic Events in Patients with Polycythemia Vera: A Real-World Observational Study

ABSTRACTBackground Polycythemia vera (PV) is a myeloproliferative neoplasm associated with an increased risk of thromboembolic and cardiovascular events. Patients and Methods This retrospective real-world cohort study used Optum's Market Clarity electronic health records (EHRs) from over 105 million US patients between 2007 to 2019 to assess the rates of thromboembolic events (TEs) in patients with low-risk, event-based high-risk (ie, prior TEs at any age), or age-based (ie, age ≥60 years without prior TEs) high-risk PV. Requirements included ≥2 PV diagnoses in a ≥60-day span, with indexing at the first PV diagnosis after ≥1 year of data. Results Among 20,089 patients with new or established PV, 25.1% experienced ≥1 post-index TE. TE incidence was 50.2% (1,634/3,256) in the event-based high-risk group, 25.0% (2,481/9,924) in the age-based high-risk group, and 13.3% (991/6,909) in the low-risk group. Overall, the most common arterial events were stroke (7.1%) and myocardial infarction/acute coronary syndrome (6.4%). Common venous events were deep vein thrombosis/deep thrombophlebitis (8.1%) and pulmonary embolism (4.5%). The strongest pre-index risk factors for TEs were history of TEs, elevated white blood cells (WBCs) >25,000/µL, and cytoreductive medication. Each 1% increase in a patient's median post-index hematocrit was associated with a 3% increase in the risk of a subsequent TE. Conclusion Although patients with a prior history of TEs had the highest thrombotic risk, all groups were at risk of developing additional TEs, highlighting the need for improved therapies that reduce the risk of TEs and other cardiovascular events in patients with PV. MicroAbstract: In this large (N=20,089), retrospective real-world study of thromboembolic events (TEs) in a broadly representative population of patients with a primary diagnosis of polycythemia vera (PV), post-index TEs were reported for 25% of patients. Significant predictors of TEs included prior TEs, elevated leukocytes, use of cytoreductive medication, and age ≥60 years. Elevated platelet counts were not a risk factor. Among patients with low-risk PV (age<60 years and no pre-index TEs), 13% had post-index TEs. These results highlight the need for more effective patient management and the development of improved PV therapies to reduce the risk of TEs.