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Low-dose aspirin reduced rate of major vascular events
Low-dose aspirin failed to significantly reduce the rate of venous thromboembolism recurrence when compared with placebo, but aspirin did significantly reduce the rate of major vascular events, according to results of the ASPIRE study.
Patients who had a first episode of unprovoked VTE have a high risk for recurrence after anticoagulant therapy. Although vitamin K antagonists have proved to effectively prevent VTE during treatment, the drugs remain unable to improve survival and are associated with increased risk for bleeding, according to background information in the study.
Previous studies have identified low-dose aspirin as a simple, affordable and readily available treatment for the prevention of VTE and arterial vascular events.
Timothy A. Brighton, MB, BS, of the Prince of Wales Hospital in Sydney, Australia, and colleagues conducted a randomized, placebo-controlled study to assess the efficacy of low-dose aspirin in preventing VTE recurrence among patients who experienced an unprovoked VTE episode and then completed anticoagulation with warfarin.
The investigation included 822 patients aged at least 18 years who completed anticoagulation therapy. The researchers randomly assigned half of the patients to aspirin 100 mg daily and half to placebo.
Patients underwent randomization at 56 sites in five countries from May 2003 to August 2011.
The researchers asked patients to take one tablet daily for a minimum of 2 years. Maximum duration of treatment was capped at 4 years.
VTE recurrence served as the primary outcome. Median follow-up was 37.2 months.
VTE recurrence occurred in 73 of 411 eligible patients (18%; per year rate of 6.5%) assigned to placebo and 57 of 411 (14%; per year rate of 4.8%) assigned to aspirin (HR=0.74; 95% CI, 0.52-1.05). The difference was not statistically significant, according to researchers.
However, aspirin reduced the rate of recurrence in major vascular events — a composite of VTE, myocardial infarction, stroke or cardiovascular death. The secondary outcome occurred in 88 patients assigned to placebo (8% per year) and 62 patients assigned to aspirin (5.2% per year; HR=0.66; 95% CI, 0.48-0.92).
Aspirin reduced the rate of VTE, MI, stroke, major bleeding or death from any cause by 33% (HR=0.67; 95% CI, 0.49-0.91), according to results from the study.
Researchers did not find significant differences between groups in the rates of major or clinically relevant non-major bleeding episodes (rate of 0.6% per year for placebo and 1.1% per year for aspirin; P=.22).
Adverse events leading to hospitalization occurred in 117 patients assigned to placebo (28%) and 102 patients (25%) assigned to aspirin.
Although the results did not show a significant reduction in the primary outcome of recurrent venous thromboembolism with aspirin, they did demonstrate that aspirin reduced major vascular events by 34% without increasing bleeding, resulting in a significant net clinical benefit, Brighton and colleagues concluded.
“The findings of the ASPIRE study, especially when considered together with [past research], provide consistent evidence that low-dose aspirin is beneficial in preventing recurrent venous thromboembolism and major vascular events in patients who have had a first episode of unprovoked venous thromboembolism,” the researchers wrote. “Thus, aspirin is an attractive option for such patients once they have completed an initial course of anticoagulation therapy.”
Disclosure: The researchers report consulting/lecture fees from, grant support from and advisory board roles with Amgen Australia, Bayer HealthCare, Boehringer Ingelheim, Bristol-Myers Squibb, Daiichi-Sankyo, Eisai, GlaxoSmithKline, Pfizer, Sanofi-Aventis and other pharmaceutical companies.
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Brighton TA. N Engl J Med. 2012;doi:10.1056/NEJMoa1210384.