One doctor went so far as to call the preliminary study a potential “game changer.”
The clots, known as venous thromboembolism or VTE, often occur in the legs. They can travel to the lungs and sometimes be fatal.
"With aspirin, a drug that is low cost, safe, and available worldwide, we can reduce by 40% the incidence of the recurrence of VTE," says Cecilia Becattini, MD, assistant professor of internal medicine at the University of Perugia in Italy.
She presented her findings at a news conference at the annual meeting of the American Society of Hematology in San Diego.
Blood Clots: Numbers, Risks
VTE occurs in about 800,000 people in North America every year, Becattini says. If the blood clot travels, it sometimes can block an artery to the lung, causing chest pain and severe shortness of breath If not treated quickly, it can be deadly.
In some cases, anti-clotting drugs such as warfarin (Coumadin, Jantoven, Marfarin) are given as treatment for a period of six to 12 months after the blood clot. However, two years after stopping the warfarin, 15% to 20% of patients have a repeat clot.
While the anti-clotting treatment can be extended beyond 6-12 months, it carries a risk of bleeding. While on the drugs, called anticoagulant therapy, patients must also get frequent blood tests to see if the dose is correct. Most find that inconvenient, Becattini says.
Aspirin Study Details
In the study, Becattini and her colleagues assigned 205 patients who had VTE to get 100 milligrams of aspirin a day and 197 patients who had VTE to get a placebo.
All had already finished 6-12 months of anticoagulant therapy. They took the aspirin or the placebo for about 24 months. They were followed for up to 36 months.
The patients taking the placebo had almost twice the amount of repeat blood clots as those taking aspirin.
In each group, one patient had a major bleeding episode, a known risk.
"It's not just an alternative [to long-term anticoagulants] but a safe alternative," Becattini says. Even so, she says, confirmation of their results is needed.
Aspirin is widely used to prevent heart attacks and strokes. It helps prevent the formation of blood clots in the arteries. However, its use as an alternative to anticoagulants to prevent clots in the veins has been debated.
A Potential 'Game Changer'?
"What this study showed was, if you put these patients on aspirin you have a 40% reduction in recurrence," says Alvin Schmaier, MD, the Robert W. Kellermeyer professor of hematology and oncology at Case Western Reserve University in Cleveland.
"That's quite startling and quite helpful," he tells WebMD.
Some previous studies have looked at the role of drugs such as aspirin to prevent repeat clots, he says. However, the results were not clear. "What's helpful about this study is it gives us an option of how to handle these patients."
"I actually think it could be a game changer," he says. He emphasizes, however, this treatment was studied only to reduce the risk of repeat blood clots.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.