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Elizabeth Cooney is a health reporter for the Worcester Telegram & Gazette.
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Wednesday, May 23, 2007

Harvard study explains how aspirin might prevent some colon cancers

Taking aspirin regularly has long been known to prevent colorectal cancer in some people, but why that’s true has been unclear.

Researchers have suspected that blocking the enzyme COX-2 might be the mechanism involved. Dr. Andrew T. Chan and his Harvard Medical School colleagues confirm a connection to COX-2 in an article to appear in tomorrow’s New England Journal of Medicine.

Analyzing data from two large observational studies, they found that regular aspirin use — two or more tablets a week for more than 10 years — reduced the risk of developing colorectal tumors with high levels of COX-2 by 40 percent but did not have any effect on tumors without COX-2.

"That’s a pretty striking difference," Chan said in an interview.

It’s too soon to suggest taking aspirin to prevent colorectal cancer, he said. At this point no one knows how to predict who will develop COX-2 negative or COX-2 positive forms of the cancer. Further studies are needed to see if people who develop polyps that are COX-2 positive, or people who had COX-2 positive tumors and are concerned about recurrence, might benefit from aspirin.

"We’re on the right track," Chan said. "Ultimately, we may reach a point of making clinical recommendations for some subset of the population to improve the methods we already have to prevent colorectal cancer," such as screening, eating a balanced diet low in red meat and maintaining a low body weight, he said. "People can do that now."

In an editorial accompanying Chan’s article, Dr. Sanford D. Markowitz of Case Western Reserve University School of Medicine echoed the article’s call for more research into other ways to inhibit production of COX-2, noting that only one-third of the COX-2 positive colorectal cancers were prevented by regular aspirin use.

"We need to ask whether there are alternative strategies for targeting the COX pathway that have better efficacy or lower rates of adverse effects," Markowitz writes.

Posted by Elizabeth Cooney at 05:12 PM
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