Stephan Moll, MD writes… Aspirin is beneficial in preventing recurrent venous thromboembolism (VTE) in patients who have had a previous episode of unprovoked VTE and who have been treated with anticoagulant therapy, a publication in the journal Circulation re-confirms this week: Aspirin reduces the risk of recurrent VTE by more than a third without significantly increasing the risk of bleeding [ref 1]. This publication does not report results of a new study, but is rather a further analysis of the previously published WARFASA and ASPIRE aspirin trials [ref 2,3].
Methods and Results
- This publication is a combined patient-level analysis of the WARFASA and ASPIRE to more accurately estimate the effects of aspirin treatment (compared to placebo) on prevention of recurrent thrombosis: overall, on individual outcomes and in prespecified subgroups of patients.
- The analysis includes 1,224 patients. (a) In the intention-to-treat analysis aspirin compared to placebo reduced recurrent VTE (7.5%/year vs 5.1%/year; hazard ratio HR 0.68; 95% CI, 0.51–0.90; P=0.008), including both DVT (HR, 0.66; 95% CI, 0.47–0.92; P=0.01) and PE (HR, 0.66; 95% CI, 0.41–1.06; P=0.08). Subgroup analyses indicate similar relative, but larger absolute, risk reductions in men and older patients. (b) After adjustment for treatment adherence, recurrent VTE was reduced by 42% (HR, 0.58; 95% CI, 0.40–0.85;P=0.005).
- The major bleeding rate was low (0.4%/year for placebo and 0.5%/year for aspirin).
Conclusion
- The analysis provides evidence that aspirin reduces the risk of recurrent VTE.
- It is clear that the treatment effect of aspirin is still much less than can be achieved with warfarin or the new oral anticoagulants, where more than an 80% reduction in VTE recurrence is achieved.
- Aspirin should be strongly considered in patients with unprovoked VTE for whom long-term anticoagulation therapy (with warfarin or one of the new oral anticoagulants) is not considered appropriate or is discontinued. However, aspirin is not a replacement for anticoagulation.
Interesting Calculation
The authors add an interesting calculation: Globally, many patients with unprovoked VTE are not routinely treated with longer-term anticoagulant therapy. A conservative estimate is that over a million patients worldwide have unprovoked VTE each year and an even greater number have a prior history of unprovoked VTE. Less than half of these patients remain on long-term anticoagulant therapy. If a million patients worldwide could be treated with aspirin each year, 100,000 events might be prevented with a minimal increase in bleeding (about 1 extra major bleed for every 25 VTEs prevented) with an inexpensive treatment.
References
- Simes J et al. Aspirin for the prevention of recurrent venous thromboembolism: The INSPIRE Collaboration. Circulation 2014 Aug 25 [Epub ahead of print].
- Becattini C et al. WARFASA Investigators. Aspirin for preventing the recurrence of venous thromboembolism. N Engl J Med. 2012;366:1959-1967.
- Brighton TA et al. ASPIRE Investigators. Low-dose aspirin for preventing recurrent venous thromboembolism. N Engl J Med. 2012;367:1979-1987.
Disclosure: I have consulted for Janssen, Daiichi, Boehringer Ingelheim.
Last updated: Aug 27th, 2014
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