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Frequency of thromboembolic and mortality events in patients with ET and PV

Mar 26, 2024
Learning objective: After reading this article, learners will be able to cite a new clinical development in essential thrombocythemia and polycythemia vera.

Thromboembolic events, including arterial and venous thromboembolic complications, are more common in patients with essential thrombocythemia (ET) and polycythemia vera (PV) than in the general population, and are associated with increased mortality and morbidity risks.1

Enblom-Larsson et al.1 performed a retrospective study investigating frequencies of thromboembolic and mortality events in a cohort of patients from the Swedish MPN register with ET or PV vs matched controls (MCs).

Study design1

  • In total, 48% and 50.2% of patients with ET and PV were treated with platelet inhibitors at diagnosis vs 17.5% and 19.4% in the MC groups, respectively.
    • Median age was 61.9 years and 70.4 years, and 58.6% and 50.6% were female, respectively.
  • Study endpoints included:
    • frequency of arterial and venous events;
    • major bleeding; and
    • all-cause stroke and all-cause mortality events.

Key findings

  • In total, 3,141 patients with ET vs 15,705 MCs and 2,604 patients with PV vs 13,020 MCs were assessed.
  • Rates of thromboembolic and mortality events were higher in patients with ET and PV vs MCs (Figure 1).
  • Arterial or venous events and all-cause mortality between patients aged 60 and 70 years differed significantly, with the latter having increased risk (p < 0.001).
    • Hazard ratio (HR) increased as age increased over 60 years in patients with ET and PV.
  • Previous comorbidities, including ischemic heart disease and hypertension, were associated with increased risk of arterial events in patients with ET vs MCs (HR: 2.39 and 1.99) and PV vs MCs (HR: 2.09 and 1.44), respectively.

Figure 1. Rate of thromboembolic and mortality events in patients with A ET and B PV vs respective matched controls* 



ET, essential thrombocythemia; PV, polycythemia vera, VTE, venous thromboembolism.

*Adapted from Enblom-Larsson A, et al.1

Key learnings 

  • Increased rates of thromboembolic events are reported in patients with ET and PV compared with MCs; specifically arterial or venous events, VTE, major bleeding, and all-cause mortality.
  • Comorbidities, including cardiovascular risk factors, and age are also associated with increased risks of thromboembolic and mortality events.
  • As patients are frequently treated with anti-platelet agents, future studies should focus on biomarkers able to identify patients with a higher risk of thromboembolic events.

  1. Enblom-Larsson A, Renlund H, Andréasson B, et al. Thromboembolic events, major bleeding and mortality in essential thrombocythemia and polycythemia vera – a matched nationwide population-based study. Br J Haematol. Online ahead of print. DOI: 10.1111/bjh.19337.


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