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July 15, 2015
Initial Treatment Plus 18 Months of Warfarin Reduces
New Blood Clot Risk

Brest, France—For patients with a first episode of pulmonary embolism, adding 18 months of warfarin therapy beyond the original 6 months of anticoagulant treatment reduced the risk of additional blood clots without a major increase in bleeding risk, according to a new French study.

The report, published online recently by the Journal of the American Medical Association, notes that the benefit was not maintained after discontinuation of anticoagulation therapy.

“Our results suggest that patients such as those who participated in our study require long-term secondary prophylaxis measures,” according to the authors, who were led by researchers from the Universite de Bretagne Occidentale in Brest, France.

Background information in the article notes that patients with a first episode of unprovoked venous thromboembolism have a much higher risk of recurrence when anticoagulant therapy is stopped after 3 to 6 months than those with venous thromboembolism provoked by a transient risk factor such as surgery.

Extending anticoagulation beyond 3 to 6 months has been shown to reduce the risk of recurrence in that high-risk population, according to study authors, who point out that most previous studies did not include follow-up of patients after treatment ended, so it was uncertain whether the benefit was maintained.

To help answer those concerns, the researchers focused on about 370 adult patients at 14 French medical centers who had experienced a first episode of symptomatic unprovoked pulmonary embolism and had been treated initially for 6 uninterrupted months with a vitamin K antagonist. The patients then were randomly assigned to warfarin or placebo for 18 months with median follow-up of 24 months. 

During the 18-month treatment period, about 3% of the patients in the warfarin group suffered the primary outcome—the composite of recurrent venous thromboembolism or major bleeding. More than four times as many, 13.5% of the placebo group, had the same result. Overall, warfarin was linked to a 78% reduction in the primary outcome, although the driver of the effect was reduced risk of recurrent venous thromboembolism; the risk of bleeding increasing to a minimal extent, according to the study.

Yet, the benefits were lost after anticoagulation was discontinued, the report notes. During the overall 42-month entire study period, the composite outcome occurred in 21% of the warfarin group versus 24% in the placebo group. Rates of recurrent venous thromboembolism, major bleeding, and unrelated death did not differ between groups, the authors report.

“Aspirin for 2 to 4 years following vitamin K antagonist therapy reduced the risk of recurrence by about 30% compared with placebo,” the authors add. “Although this 30% risk reduction may be viewed as small compared with the 80% or 90% usually reported with anticoagulation, and it is uncertain whether our results apply to newer anticoagulants, both aspirin and new anticoagulants may represent valuable alternatives to vitamin K antagonists or no treatment.”



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