Does Aspirin Reduce the Risk of Colon Cancer?

INDIANAPOLIS -- Americans take 29 billion aspirin tablets each year. Could aspirin have an anti-cancer effect and reduce the risk of colon cancer, the second leading cause of cancer-related death in the U.S.?

In the Perspective column of the March 6, 2003 New England Journal of Medicine, gastroenterologist Thomas F. Imperiale, M.D., professor of medicine at the Indiana University School of Medicine and a research scientist at the Regenstrief Institute, Inc., comments on two multicenter clinical studies (published in the same issue of the NEJM) that sought to answer this question. From Dr. Imperiale’s perspective, the modest benefits of aspirin found in the studies do not outweigh the risks associated with long-term aspirin use - gastrointestinal bleeding, intracranial hemorrhage and peptic ulcers. He believes further research is needed before the question posed in the first paragraph can be answered.

The first study randomized men and women cured of colon cancer to either a regular dose (325 milligrams) of aspirin or a placebo (sugar pill). The second study followed individuals who had precancerous polyps known as adenomas removed. These individuals were randomized to either the regular dose of aspirin or a low dose (81 milligrams). Both studies excluded individuals who were unable to tolerate aspirin or were already taking it for cardiovascular disease.

In the study of those who had previously had colon cancer, 17% of the aspirin group and 27% of the placebo group developed new precancerous polyps during the 31-month study. While the number of polyps was lower, indicating a reduced risk of disease for the aspirin takers, the size of the polyps was not.

In the study involving patients with previous precancerous polyps, while the lower dose of aspirin reduced risk of polyps likely to progress to cancer, the standard dose did not.

Did these studies show that aspirin has an anti-cancer effect? According to Dr. Imperiale, the studies showed that the anti-cancer benefit of aspirin is small - too small to replace the need for colon cancer screening. “The studies indicate that aspirin can work by moderately reducing the risk of recurrent polyps but larger and longer-term trials are needed to determine whether aspirin can reduce the frequency or intensity of screening exams. Until these studies are completed, aspirin should not be substituted for colon cancer screening or surveillance.”

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Media Contact: Cindy Fox Aisen
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caisen@iupuil.edu

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