Preventing Polyps

By Sanjay Gupta, M.D.

The more doctors learn about aspirin, the more impressed they are with what it can do. Not only does this cheap, century-old drug (derived originally from the bark of the willow tree) relieve pain and ward off heart attacks, but now there is also strong evidence that it is one of the few compounds that offer real protection against colon cancer, the second leading cause of death from cancer in the U.S. The results of two studies published in last week's New England Journal of Medicine clearly show that taking aspirin every day--in low or high doses--reduces the number and size of polyps, the small precancerous growths in the lining of the colon that are usually benign but can sometimes turn into malignant tumors.

What makes these studies particularly compelling is the rigorous fashion in which they were conducted. Patients were randomly assigned treatment with aspirin or a placebo, and neither the patients nor the doctors knew who was getting which pill. The results of one of the studies were so striking that it was stopped early; the researchers felt it would be unethical to continue giving a placebo to half the participants.

Does this mean that everybody should start taking daily doses of aspirin? Not necessarily. Aspirin, after all, carries its own risks, including internal bleeding, stomach ulcers, allergies and in rare cases strokes. The patients in these two studies were selected because they were known to be at high risk for colon cancer--which tended to tip the risk-benefit ratio in their favor. Whether daily aspirin use makes sense for the rest of us is still not clear.

It's also not clear exactly how aspirin works to ward off polyps. There is evidence to suggest that it slows down the enzyme known as cyclo-oxygenase 2, or COX-2, which seems to play a role in spurring cell growth that can lead to tumors. But for reasons no one can yet explain, higher doses of aspirin didn't translate into more protection. In one of the studies reported last week, more patients in the group taking full-strength, 325-mg aspirin pills developed colon cancer (10.7%) than in the group taking so-called baby, or 81-mg, aspirin (7.7%). The cancer rate in the placebo group, by contrast, was 12.9%.

If you and your doctor decide that you should start taking low-dose aspirin therapy, be sure you use the right pills. Although there is reason to suspect that other anti-inflammatory drugs, such as Advil and Motrin or the newer COX-2 inhibitors Vioxx and Celebrex, might offer similar protection, only aspirin has been rigorously tested. Tylenol (acetaminophen) is not an anti-inflammatory, so don't expect it to protect you against colon or any other cancer.

In a perspective accompanying the new studies, Dr. Thomas Imperiale, a gastroenterologist at Indiana University School of Medicine, takes pains to remind readers that aspirin alone is not a substitute for regular colonoscopy screenings, which enable doctors to locate and snip off growths before they become cancerous. It is also worth remembering that there are other ways to prevent colon cancer, including reducing the saturated fats in your diet and increasing your intake of folate-rich leafy green vegetables. You should probably also limit your consumption of red meat, processed meats and refined carbohydrates. And if you smoke, you should definitely quit.

Dr. Gupta is a neurosurgeon and CNN correspondent