A pill widely taken to prevent heart attack and stroke may also guard against cancer, new research suggests.
Warfarin is an inexpensive blood thinner. It's typically prescribed for patients whose leg arteries are prone to clots and for patients with the abnormal heartbeat called atrial fibrillation.
Now, Norwegian investigators say it may also protect against any type of cancer and from prostate, lung and breast cancer, in particular.
Lower colon cancer risk was also reported, but only in people taking warfarin for A-fib, according to the study.
The findings don't prove that warfarin reduces the risk of cancer, cautioned lead researcher James Lorens.
"This is an observational study using data on more than 1.25 million people 50 and older from Norwegian national registries, and cannot prove a cause-and-effect relationship," said Lorens, a professor of biomedicine at the University of Bergen in Norway.
Among adults taking warfarin, however, fewer developed cancer compared with those not taking the drug, Lorens said.
This study suggests there is something about warfarin that might reduce the risk of cancer, said Dr. Len Lichtenfeld, deputy chief medical officer at the American Cancer Society.
However, "the study does not suggest that we should be prescribing warfarin to reduce cancer risk," he said. "No one should be taking warfarin as a cancer prevention measure."
Lichtenfeld added that a healthy diet and exercise are better ways to prevent cancer than taking warfarin.
Experimental cancer models have found that warfarin blocks a receptor called AXL on tumor cells, which might explain why it could prevent cancers, he said.
As a blood thinner, warfarin works by blocking vitamin K, which is essential for clotting. But the drug is difficult to regulate, and frequent blood tests are needed to ensure the dose is high enough to prevent clotting, but not so high as to cause major bleeding.
New drugs that don't need such careful monitoring, such as Xarelto (rivaroxaban) and Eliquis (apixaban), have started to replace warfarin.
