Abstract
Abstract 543
A recurrence occurs in 15–20% of patients with unprovoked venous thromboembolism (VTE) in the two years after the withdrawal of oral anticoagulant treatment. Extending anticoagulant treatment is effective but associated with increased bleeding risk. We assessed the efficacy and safety of aspirin for the prevention of VTE recurrence after a conventional course of oral anticoagulation.
Warfasa was an investigator-initiated double-blind randomized placebo-controlled event-driven study. Patients with a first-ever unprovoked VTE who had completed 6–12 months of oral anticoagulant treatment were randomized to receive aspirin, 100 mg daily, or placebo for at least two years. The primary efficacy outcome was objectively confirmed recurrent symptomatic VTE and VTE-related death. Clinically relevant (major and non-major) bleeding were the main safety outcome. All outcome events were blindly adjudicated by an independent committee.
A VTE recurrence occurred in 27 of the 205 patients who received aspirin and 42 of the 197 patients who received placebo (6.3% versus 11.0% patient-years; hazard ratio, 0.57, 95% CI 0.35 to 0.93) during the study period (mean 24 months) (Figure A). While on study treatment, 22 and 38 patients who received aspirin or placebo, respectively had a recurrence (5.7% versus 10.7% patient-years; hazard ratio, 0.54, 95% CI 0.32 to 0.91) (mean on-treatment period 22 months) (Figure B). One patient in each treatment group had a major bleeding, with a similar incidence of clinically relevant non-major bleeding.
Aspirin reduces by about 40% the risk of recurrence in patients with unprovoked VTE without increasing bleeding, when given after a 6–12 month anticoagulant treatment. For its safety, practicality and low cost, aspirin is a valid alternative to oral anticoagulants in the extended treatment of VTE.
No relevant conflicts of interest to declare.
