Background: Thrombosis is a major cause of morbidity and mortality in patients with polycythemia vera (PV). Aspirin and hematocrit control are key components of PV management to reduce thrombotic events. However, patients with PV are also at risk for hemorrhagic complications, especially in the context of acquired Von Willebrand syndrome.
A systematic review conducted in 2013 identified 2 randomized control trials (RCTs) and concluded that low-dose aspirin does not increase the risk of major bleeding and is associated with a statistically non-significant reduction in fatal thrombotic events. The risks and benefits of other antithrombotics and the optimal management of thrombosis in patients with PV remains uncertain.

Aims: To examine the association between antithrombotic therapy and outcomes such as bleeding, thrombosis, and mortality in patients with PV. To summarize all available data, observational studies were included.

Methods: Databases including MEDLINE, CENTRAL, and Pubmed were searched. Articles examining antithrombotic use in patients with PV were included. Screening, full text review, and data extraction and risk of bias assessment were completed by 2 independent reviewers. The protocol was registered on PROSPERO (CRD42017079688).

Results: 4523 studies were identified and 12 studies (9 observational studies and 3 RCTs) were included. Antithrombotics (antiplatelets + anticoagulants) were associated with a lower risk of thrombosis (RR 0.83, CI 0.54 – 1.26, I² 70%), increased bleeding (RR 1.07, CI 0.77 – 1.50, I² 5%) and decreased all cause mortality (RR 0.65, CI 0.42 – 0.99, I² 25%). Most studies were observational and at high risk of bias. There were insufficient data for subgroup analyses of direct oral anticoagulants.

Conclusions: In PV patients, use of antithrombotics is associated with reductions in all-cause mortality (35%) and thrombosis (17%), and a statistically non-significant increase in bleeding (7%). Further prospective studies regarding antithrombotics in patients with PV are required given the uncertainty in the evidence.

[Figure 1. Forest plot of the association between antithrombotic therapy and thrombotic events in patients with polycythemia vera.]

[Figure 2. Forest plot of the association between antithrombotic therapy and all cause mortality in patients with polycythemia vera]

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/risks-and-benefits-of-antithrombotic-therapy-in-polycythemia-vera-a-systematic-review/