Ask Dr. K: Cancer risk lower with daily Aspirin

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DEAR DOCTOR K >> I read that aspirin might help to prevent cancer. Is there anything to this idea?

DEAR READER >> Open any medicine cabinet in America and you're likely to find a bottle of aspirin. Aspirin has been on the market for more than 110 years. It's an old standby for fighting fever, quieting inflammation and reducing pain. For some, it can help prevent a heart attack or stroke. And growing research points to a possible new benefit for this old friend — reducing the risk of dying from cancer.

Aspirin is one of a group of medicines known as nonsteroidal anti-inflammatory drugs (NSAIDs). Other NSAIDs include ibuprofen (Motrin, Advil) and naproxen (Aleve).

Aspirin works by inhibiting two enzymes, COX-1 and COX-2. It's aspirin's effect on COX-2 that comes into play with cancer prevention.

COX-2 triggers the production of chemicals that cause fever, trigger inflammation in joints and other tissues, and aggravate pain. By inhibiting COX-2, aspirin fights inflammation, pain and fever.

The same COX-2 enzymes that provoke pain, inflammation and fever may have a role in promoting the growth and spread of certain cancers. Of course, COX-2 is far from the only thing that contributes to the wild growth of cancer cells. But scientists have found that many of the most aggressive colon cancers have unusually high levels of COX-2. So do many prostate cancers.

An analysis of eight high-quality, randomized trials looked at whether taking a daily aspirin could reduce the risk of dying from cancer. The trials covered 25,570 people who had taken aspirin every day for at least four years. In these study subjects, daily aspirin reduced the risk of dying from cancer by 21 percent.

The analysis further showed that aspirin was most effective against gastrointestinal cancers. In particular, pancreatic, colorectal and esophageal cancers showed the largest benefit.

The benefit of aspirin was similar in men and women, and in smokers and non-smokers. On the other hand, older people benefited more than younger people.

Volunteers who took aspirin for the longest amount of time had the greatest protection against cancer death. And a daily dose of just 81 milligrams a day (one "baby" aspirin) was as effective as much higher doses. That's the same low dose taken for heart attack prevention.

So far, so good. But this is where it gets complicated. Like any other medicine, aspirin can have side effects. Bleeding is the most important. Bleeding in the gut — such as from an ulcer in the stomach, or from a leaky blood vessel (called an "AV malformation") in the intestine — can cause major blood loss. More dangerous is sudden bleeding in the brain. While such serious bleeding is very unusual, particularly in people taking low doses of aspirin, it can happen.

With virtually every type of treatment, you need to balance the good it will do against the harm it may cause. I don't think we know enough about that balance yet to recommend that most people take a regular daily aspirin to prevent cancer. But if ongoing research continues in a positive direction, that may change.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.


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