Screening and prevention
Colon cancer deaths in the United States could be cut by as much as two-thirds, scientists estimate, if everyone underwent routine screening after age 50 and made lifestyle choices such as exercising and eating healthfully. It's important to talk to one's doctor about colorectal cancer risk and when and how to be screened. The test options include a colonoscopy (the most comprehensive exam), sigmoidoscopy (which probes only the lower third of the colon), barium enema, and a test for blood in the stool.
Cancer can occur anywhere along the inside lining of the large intestine, a six-foot-long tube that includes the colon and rectum. Changes in the genetic material inside colon cells initially produce a precancerous polyp, or fleshy growth, and some polyps then become cancerous tumors. Removal of the polyps prevents cancer. If not removed, some polyps progress to become tumors in the wall of the colon, and, if they spread outside the intestine, the disease is difficult to cure.
Much of what is known about preventing colon cancer has emerged from large, long-running epidemiological studies such as the Nurses' Health Study and the Health Professionals' Follow-up Study run by Brigham and Women's Hospital, Harvard Medical School, and the Harvard School of Public Health. When the researchers compared people who did and did not develop colon cancer, they spotted several differences in diet and behavior. Among them:
Exercise: "There are 53 studies showing exercise cuts your risk by 50 percent" if you do the equivalent of jogging for half an hour, three to four times a week, says Charles Fuchs, MD, MPH, of the CGO, an expert on colon cancer risk factors.
Avoid red meat: Frequent eating of red meat raises the risk of developing colon cancer. "Red meat consumption is a very strong risk factor," says Fuchs, adding that it's especially carcinogenic if cooked to high temperatures. Compounds created in cooking muscle meat, called "heterocyclic amines," are believed to contribute to colon cancer.
Stay slim: Weight control helps prevent cancer in general, and people who are obese have a 50 percent greater chance of getting colon cancer. A low-fat diet high in fruits, vegetables, and fiber has long been touted as a colon cancer preventative, but the validity of this advice has been challenged. A study published in the New England Journal of Medicine in 1999 by Fuchs and colleagues at the Harvard School of Public Health disputed the supposed power of fiber, finding it had no measurable benefit on colon cancer risk. While eating plenty of fruits and vegetables is associated with better health in general, studies haven't documented a strong link to lowering colon cancer risk by this practice.
Take folic acid: Studies of people with a family history of colon cancer have revealed that extra folic acid — best taken in multivitamin pills — significantly cut their risk. Calcium is another supplement that may reduce risk.
Medication: Some non-steroidal, anti-inflammatory drugs (NSAIDs) have been associated with cancer. Many people use aspirin to ward off heart attacks, but whether this helps avoid colon cancer isn't known. Currently, a large, randomized clinical trial is testing this "chemopreventive" strategy using the NSAID drug celecoxib, whose trade name is Celebrex.
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