Abstract 16651: Cost-Effectiveness of Extended Duration Venous Thromboembolism Prophylaxis with Aspirin

Abstract

Introduction: The risk of a recurrent event following discontinuation of guideline recommended warfarin therapy has been estimated to be as high as 20% in those suffering their first episode of venous thromboembolism (VTE). The Aspirin for the Prevention of Recurrent Venous Thromboembolism (WARFASA) trial demonstrated extending the duration prophylaxis with aspirin can reduce recurrent VTE risk by 42% compared to placebo, without increasing bleeding. We sought to estimate the cost-effectiveness of extended duration prophylaxis of VTE with aspirin.

Methods: A Markov model was developed to estimate the cost-effectiveness of 2 years of extended duration prophylaxis with aspirin (100 mg daily). The analysis was conducted from the Medicare perspective using data from the WARFASA trial and other published studies of anticoagulation. The base-case analysis assumed a theoretical cohort of 60 year old patients experiencing their first unprovoked VTE and initially treated with 6-18 months of warfarin (international normalized ratio=2.0-3.0). We utilized a one month cycle length and a discount rate of 3%/year. Evaluated outcomes included treatment costs (2011US$) following the discontinuation of initial warfarin treatment, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs).

Results: Total costs/patient over the 2 year trial duration were $1,930 for aspirin and $2,848 for placebo, respectively. Corresponding QALYs were 1.910 and 1.906, making extended duration prophylaxis with aspirin an economically dominant strategy. When the model was extrapolated to a lifetime, aspirin was again dominant with treatment costs of $12,635 and $13,877 for aspirin and placebo, respectively, and corresponding QALY estimates of 15.123 and 15.020. Results remained robust upon one-way sensitivity analysis. Monte Carlo simulation demonstrated extended duration prophylaxis with aspirin would be a dominant strategy in 99% of 10,000 iterations over a lifetime.

Conclusion: Our model suggests extending the duration of prophylaxis with aspirin in patients suffering their first episode of unprovoked VTE will result in cost savings and additional QALYs lived when modeled over WARFASA’s 2 year trial duration and a lifetime.