Study examines risk factors associated with colorectal cancer

December 09, 2003

Smoking, drinking alcohol at or above moderate levels, or having a first degree relative with colorectal cancer, are associated with an increased risk for having serious colon polyps, according to an article in the December 10 issue of The Journal of the American Medical Association (JAMA).

Colorectal cancer is the second leading cause of cancer death in North America, according to background information in the article. Evidence exists that screening asymptomatic populations beginning at age 50 years can reduce death due to colorectal cancer and that removal of precursor tumors may reduce the incidence of colorectal cancer. Identification of important risk factors for advanced colonic tumors could inform both risk stratification and development of risk reduction strategies. Few studies have evaluated risk factors for advanced colorectal tumors in asymptomatic individuals, compared risk factors between persons with and without polyps, or included most purported risk factors in a multivariate analysis.

David A. Lieberman, M.D., of the Department of Veterans Affairs Medical Center, Portland, Ore., and colleagues conducted a study to determine the risk factors associated with advanced colorectal neoplasia (tumors) in a group of asymptomatic persons with complete colonoscopy. The study, conducted between February 1994 and January 1997, included 3,121 asymptomatic patients aged 50 to 75 years from 13 Veterans Affairs medical centers. All participants had complete colonoscopy to determine the prevalence of advanced neoplasia. Variables examined included history of first-degree relative with colorectal cancer, prior cholecystectomy (surgical removal of the gall bladder), serum cholesterol level, physical activity, smoking, alcohol use, and dietary factors.

A total of 329 participants had advanced neoplasia and 1,441 had no polyps. The researchers found positive associations for history of a first-degree relative with colorectal cancer (66 percent increased risk), current smoking (85 percent increased risk), and current moderate to heavy alcohol use and colon neoplasia.

Patients had a lower risk for advanced neoplasia with cereal fiber intake (greater than 4.2 grams/.15 ounces a day), vitamin D intake of greater than 645 IU/d, and daily use of nonsteroidal anti-inflammatory drugs (NSAIDs, 34 percent lower risk). Marginal factors included physical activity, daily multivitamin use, and intake of calcium and fat derived from red meat. No association was found for body mass index, prior cholecystectomy, or serum cholesterol level. Risk variables were similar to those for patients with no polyps, except that past and current smoking were associated with an increased risk of polyps.

" ... it is prudent to recommend that patients stop smoking, reduce alcohol intake, and exercise regularly as part of general preventive health measures," the authors write. "Consuming vitamin D plus a calcium supplement or regular dairy products represents a low-risk strategy that may benefit patients. The benefit of a daily multivitamin is uncertain and requires further study but is associated with very low risk to patients. The strong association with family history of colorectal cancer reinforces existing recommendations to offer screening with colonoscopy. The potential protective effect of NSAIDs must be carefully balanced against the risks. Further study is needed to determine if risk factors at baseline colonoscopy are predictive of future incidence or recurrence of advanced neoplasia." (JAMA. 2003;290:2959-2967. Available post-embargo at
Editor's Note: This study was supported by the Cooperative Studies Program, Department of Veterans Affairs. Co-author Dr. Prindiville was supported in part by a career development award from the Cancer Research Foundation of America and the National Cancer Institute.

The JAMA Network Journals

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