Medical Edge Newspaper Column

Nipping Colon Cancer In The Bud

July 24, 2006
DEAR MAYO CLINIC:
A friend of mine recently had a colonoscopy. His doctor found, and zapped, 12 polyps in his colon -- all of them small and, as it turned out, benign. An earlier procedure, done six years ago, found none. What could explain the big change and what, if anything, should he do to prevent any further polyp formation, which can be a precursor to colon cancer?

ANSWER:
First, let me commend him for choosing to have the initial procedure and then following up. The best way to prevent colon cancer is to perform such screening at regular intervals. When discovered during a colonoscopy -- in which a long, slender tube attached to a video camera allows the doctor to view the patient's entire colon -- polyps can be removed by an accompanying device that cuts and cauterizes (burns) them.

The vast majority of colon cancers begin as small and innocuous polyps. Some types of polyps will never become malignant; others, termed precancerous, might eventually progress if left in place long enough. But, as your friend's experience attests, colon polyps can be detected and excised long before they become worrisome, provided that patients do their part -- by showing up. While one in five middle-aged and older adults may harbor colon polyps, many people avoid colonoscopy because of its slight discomfort and inconvenience.

The change in your friend's case may seem sudden, but the fact is that after six years -- or possibly even longer, as some of the polyps may have been present during the initial screening but were too tiny to detect -- all of the polyps were still small and benign. In fact, given the slowly progressing nature of these formations, we generally recommend a colonoscopy exam only once every 10 years for the average person over 50. However, for patients who have had previous polyps or a family history of colon polyps or cancer, the recommended interval between colonoscopies can range from one to five years.

Because we don't precisely know what causes polyps to form, there is no sure way to prevent their occurrence. But there are risk factors. These include:

Age (the great majority of people with colon polyps and colon cancer are 50 or older); ethnicity (African-Americans have higher rates than do other ethnic groups); family history (you're more likely to develop colon cancer, both because of genes and a shared environment, if you have a parent, sibling, or child with the disease); tobacco use (risks increase with both the amount and duration of smoking history); alcohol (excessive consumption makes polyp development more likely); a sedentary lifestyle (when you're inactive, waste stays in your colon longer, thereby increasing exposure time to any carcinogens present); diet (excessive consumption of fat, especially from animal sources, may introduce carcinogens into the colon; and low-fiber foods can keep them in there longer); and obesity (extra body fat, which appears to encourage the growth of cells in the colon and rectum, has been linked to colorectal cancer).

While we cannot control the first three risk factors above, we can certainly do a great deal about the others by eating a healthy diet -- fruits, vegetables and whole grains -- getting enough physical activity, keeping weight down, not smoking, and consuming alcohol in moderation (if at all). These "smart lifestyle" choices make sense not only for preventing colon cancer but also for numerous other illnesses.

It's also worth consulting with one's doctor on whether to take aspirin, vitamin supplements or other agents that have shown in early clinical research studies to have some encouraging potential to reduce colon polyps and cancer. Be aware that these relatively simple, pill-based prevention options might not be appropriate for everyone.

At present, the best prevention method of all is what your friend is already doing -- undergoing regular surveillance exams every few years. Studies have shown that the practice of searching for and removing polyps through colonoscopy can reduce the rate of colon-cancer incidence by some 90 percent. And if routine screening does detect early-stage cancers, which are then usually removable as well, the five-year survival rate may also be as high as 90 percent.

-- Paul J. Limburg, M.D., Gastroenterology, Mayo Clinic, Rochester, Minn.