Key result
Aspirin did not significantly reduce the rate of recurrent venous thromboembolism compared to placebo (4.8% vs 6.5% per year; HR 0.74; 95% CI 0.52-1.05; P=0.09).
Why the study?
Does aspirin 100 mg daily reduce the recurrence of venous thromboembolism in patients who have completed initial anticoagulant therapy after a first episode of unprovoked venous thromboembolism?
RCT (n=822)
Does aspirin 100 mg daily reduce the recurrence of venous thromboembolism in patients who have completed initial anticoagulant therapy after a first episode of unprovoked venous thromboembolism?
Effect estimate: HR 0.74 (95% CI 0.52-1.05)
Absolute Event Rate: 4.8% vs 6.5%
p-value: p=0.09
Low-dose aspirin after initial anticoagulation for unprovoked VTE did not significantly reduce VTE recurrence but significantly reduced major vascular events without increasing bleeding risk.
Aspirin does not significantly prevent recurrent VTE; extends evidence on major vascular event reduction without excess bleeding.
BACKGROUND: Patients who have had a first episode of unprovoked venous thromboembolism have a high risk of recurrence after anticoagulants are discontinued. Aspirin may be effective in preventing a recurrence of venous thromboembolism. METHODS: We randomly assigned 822 patients who had completed initial anticoagulant therapy after a first episode of unprovoked venous thromboembolism to receive aspirin, at a dose of 100 mg daily, or placebo for up to 4 years. The primary outcome was a recurrence of venous thromboembolism. RESULTS: During a median follow-up period of 37.2 months, venous thromboembolism recurred in 73 of 411 patients assigned to placebo and in 57 of 411 assigned to aspirin (a rate of 6.5% per year vs. 4.8% per year; hazard ratio with aspirin, 0.74; 95% confidence interval [CI], 0.52 to 1.05; P=0.09). Aspirin reduced the rate of the two prespecified secondary composite outcomes: the rate of venous thromboembolism, myocardial infarction, stroke, or cardiovascular death was reduced by 34% (a rate of 8.0% per year with placebo vs. 5.2% per year with aspirin; hazard ratio with aspirin, 0.66; 95% CI, 0.48 to 0.92; P=0.01), and the rate of venous thromboembolism, myocardial infarction, stroke, major bleeding, or death from any cause was reduced by 33% (hazard ratio, 0.67; 95% CI, 0.49 to 0.91; P=0.01). There was no significant between-group difference in the rates of major or clinically relevant nonmajor bleeding episodes (rate of 0.6% per year with placebo vs. 1.1% per year with aspirin, P=0.22) or serious adverse events. CONCLUSIONS: In this study, aspirin, as compared with placebo, did not significantly reduce the rate of recurrence of venous thromboembolism but resulted in a significant reduction in the rate of major vascular events, with improved net clinical benefit. These results substantiate earlier evidence of a therapeutic benefit of aspirin when it is given to patients after initial anticoagulant therapy for a first episode of unprovoked venous thromboembolism. (Funded by National Health and Medical Research Council [Australia] and others; Australian New Zealand Clinical Trials Registry number, ACTRN12605000004662.).
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Brighton et al. (2012) conducted an RCT in First episode of unprovoked venous thromboembolism (n=822). Aspirin vs. Placebo was evaluated on Recurrence of venous thromboembolism (HR 0.74, 95% CI 0.52-1.05, p=0.09). Aspirin did not significantly reduce the rate of recurrent venous thromboembolism compared to placebo (4.8% vs 6.5% per year; HR 0.74; 95% CI 0.52-1.05; P=0.09).
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