According to Cecilia Becattini, MD, of the University of Perugia, Perugia, Italy, and colleagues, aspirin reduces by about 40% the risk of recurrence in patients with unprovoked venous thromboembolism (VTE) without increasing bleeding, when given after a 6-12 month anticoagulant treatment.
The WARFASA trial 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. Confirmed recurrent symptomatic VTE and VTE-related death was the primary efficacy outcome. Clinically relevant (major and non-major) bleeding were the main safety outcome. All outcome events were blindly adjudicated by an independent committee.
According to Dr. Becattini, a VTE recurrence was noted in 27 of the 205 patients who received aspirin and 42 of the 197 patients who received placebo (6.3% vs 11.0% patient-years; hazard ratio [HR] 0.57) during the study period (mean 24 months). Correspondingly, 22 of 38 patients who received aspirin or placebo, respectively, had a recurrence (5.7% vs 10.7% patient-years; HR, 0.54) (mean on-treatment period 22 months). One patient in each treatment group had a major bleeding, with a similar incidence of clinically relevant non-major bleeding.
The researchers concluded that “For its safety, practicality and low cost, aspirin is a valid alternative to oral anticoagulants in the extended treatment of VTE.”