You probably saw the recent headline: Colonoscopy may not be as effective as previously thought at detecting the precursors of colorectal cancer. But whether the procedure finds 60 percent of polyps, as the new research suggests, or 90 percent, it's still the most effective screening test, other than the Pap smear, for any kind of common cancer. Unlike a mammogram or a PSA test, a colonoscopy can even be thought of as a form of prevention, since it enables the doctor to get rid of polyps before they become malignant. Even critics of many forms of cancer screening say it has its place. And yet fewer than half the eligible people—those age 50 and older, assuming average risk—are getting either a colonoscopy or another of the recommended screening tests for colorectal cancer.
The lesson from the new research is not that a colonoscopy isn't worth the yuck factor or the expense but that you should make sure yours is as well performed as possible. "You should have a colonoscopy done by a person who does a lot of them and does them well," says David Weinberg, a gastroenterologist who chairs the department of medicine at the Fox Chase Cancer Center in Philadelphia. Researchers have tried to define the quality of colonoscopies: One study, published in 2006 in the New England Journal of Medicine , found that doctors who took at least six minutes to withdraw the colonoscope from the intestinal tract found more polyps than those who didn't.
Another metric relates to the number of colonoscopies performed by the doctor. Sidney Winawer, an attending gastroenterologist at Memorial Sloan-Kettering Cancer Center, says you should opt for someone who does at least five a week. Yet another measure relates to the percentage of colonoscopies in which polyps are removed, he says: It should reflect what we know to be the prevalence of polyps in the population, which is about 25 percent for men and 15 percent for women. Of course, it may not be possible to ask about all these metrics when you call up for an appointment. In that case, "you have to rely on your primary-care physician" to guide you to a specialist, says Winawer. Ask for a recommendation.
The doctor's expertise is one part of the colonoscopy quality equation. The bowel-cleansing prep is another. It's harder to detect polyps, especially the flat kind, if your insides aren't as immaculate as possible. So follow the directions, says Weinberg. There are different variations on the prep, which is basically a clear liquid diet for some period of time and laxatives; some doctors will recommend half the laxative be taken at night and the other half in the morning of the test, while some prefer a clear liquid diet for a longer-than-usual time. But following to the letter whichever version your doctor recommends is the best way to ensure he or she will be able to get a good look at the walls of your bowel.
The colonoscopy isn't perfect; few medical procedures are. And no screening test can give you a 100 percent guarantee that you won't get colon cancer. But follow the usual guidelines for a healthy life—eat a balanced diet that is heavy on fruits and veggies and whole grains and light on saturated fat, don't smoke, get plenty of exercise, and keep your alcohol intake in check—and adhere to the recommended screening schedule for colorectal cancer. You'll know you've done what you can to cut the risk of the disease.