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>  News Releases >   2003 >   March

Daily aspirin helps prevent colon cancer

Posted 03/22/03, by Deborah Kimbell

John Baron, Professor of Medicine and of Community and Family Medicine, leads a team of researchers that found that a small daily dose of aspirin helps prevent precancerous polyps and it may reduce colorectal cancer.
(photo by Mark Austin-Washburn)
Study will appear in the New England Journal of Medicine

A seven-year study led by Dartmouth Medical School researchers shows that a daily dose of aspirin can be effective in reducing the risk of colon adenomas — benign tumors that can develop into cancer if left in the bowel.

The study, conducted jointly by doctors and researchers from Norris Cotton Cancer Center at Dartmouth-Hitchcock Medical Center in Lebanon, N.H., and at several other institutions across North America, confirms indications from nonrandomized studies that low-dose aspirin may protect against cancers of the colon and rectum. The final results of the study were published in the March 6 issue of the New England Journal of Medicine (NEJM).

John Baron, Professor of Medicine and of Community and Family Medicine, was lead author of the article, and co-author of another report in the NEJM that also found that aspirin protected against adenomas of the colon and rectum. He noted that the findings of the two studies show that low doses of aspirin do protect against the pre-cancerous polyps, and so there is good reason to believe aspirin probably reduces rates of colorectal cancer itself. This will be particularly valuable for people who are at increased risk for cancer because they have had colon adenomas (polyps) or because they have previously been treated for colorectal cancer.

The randomized, double-blind study, conducted between 1994 and 2001, looked at more than 1,100 patients with previously diagnosed colorectal adenomas. Some patients received aspirin — either 81 milligrams or 325 milligrams — while others received a placebo. Interestingly, the group receiving the smaller dose of aspirin — 81 milligrams, or the equivalent of one baby aspirin — showed a lower incidence of recurring polyps than did those treated with the larger dose of aspirin — 325 milligrams or the equivalent of a standard adult aspirin.

Overall, those treated with a daily dose of baby aspirin found their risk of polyps reduced 19 percent and their risk of advanced lesions reduced by more than 40 percent.

A companion study, conducted among patients with a history of cancer of the colon or rectum, tested a regular aspirin tablet (325 milligrams) against placebo. It showed even larger reductions in the occurrence of adenoma — about a 35 percent reduction.

Although aspirin is generally a safe drug, Baron noted that it can have adverse effects for some individuals. Before people embark on a daily aspirin regimen, they should check with their doctors, he said. And, he stressed that just taking aspirin is not enough to assure freedom from colon cancer.

"Aspirin is not a magic bullet. Although the incidence was reduced, all the polyps didn't go away in our study. Regular screenings, perhaps including colonoscopies, are still important," he said.

- Deborah Kimbell

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