What's New Regular use of aspirin significantly reduces risk of colon cancer, but only at doses that increase risk of intestinal bleeding.

That finding from a large-scale, long-term study was a letdown for those who hoped low-dose aspirin therapy -- such as a daily baby aspirin (80 milligrams), which has been shown to cut risk of heart disease -- might also prevent colon cancer. But researchers found the greatest reduction in colon cancer risk -- 53 percent -- among women who took more than 14 standard aspirin tablets (325 milligrams each) weekly for over 10 years. For every one or two cases of colon cancer prevented, researchers said, the aspirin would cause eight additional cases of serious bleeding.

The Study Published last week in the Journal of the American Medical Association, the study analyzed data collected from 82,911 initially cancer-free female nurses over 20 years.

"We found that the dosage you need to prevent heart disease is quite different from the one that one needed to reduce the risk of invasive colorectal cancer," said lead author Andrew Chan, a gastroenterologist at Massachusetts General Hospital. "There's no one easy solution for people." Chan said the findings apply to men.

According to the American Cancer Society, about 145,000 new cases of colon cancer and 56,000 deaths are expected in the U.S. in 2005, making it the leading cause of cancer death after lung cancer.

Waiting on Answers What about aspirin for people who have had colon cancer or are at high risk due to family history or colorectal polyps? Previous studies have found that daily aspirin lowered risk in people with a history of colon cancer or colorectal polyps (benign tumors that can lead to colon cancer), but there is no commonly accepted recommendation for aspirin, even for cancer survivors. Paul Limburg, director of the gastrointestinal neoplasia clinic at the Mayo Clinic in Rochester, Minn., said researchers are working on risk assessments for aspirin use vis-a-vis cancer. "There probably are groups where the benefits of aspirin outweigh risk, but we don't know yet where to set that bar," he said.

-- Elizabeth Agnvall

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