Risk of Thromboembolic Events in Patients With Polycythemia Vera: A Real-World Observational Study.
Key claim: In a large US real-world PV cohort, thromboembolic events occurred in all risk groups—highest after prior TEs—and each 1% rise in median post-index hematocrit was associated with a 3% increase in subsequent TE risk.
Abstract
BACKGROUND: 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 from over 105 million US patients between 2007 and 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% (1634/3256) in the event-based high-risk group, 25.0% (2481/9924) in the age-based high-risk group, and 13.3% (991/6909) 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 a history of TEs, elevated white blood cells > 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.
Why this matters
PV’s natural history is dominated by thrombosis, and this real-world cohort adds a quantitative dose-response link between hematocrit control and TE risk (~3% higher risk per 1% HCT rise) that reinforces the <45% target as more than a categorical threshold. It also confirms that prior TE is the strongest recurrence driver, sharpening secondary-prevention priorities and complementing the existing PV-page evidence on inadequate real-world HCT control and predictive-factor studies in high-risk PV.