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Detecting—and Even Preventing—Colon Cancer
For: Best Bets for Preventing Colon Cancer, June 2002

Colorectal cancer kills more people in the U.S. and Canada every year than any other cancer except lung cancer. Yet this disease, which includes cancers of the colon (large intestine) and rectum, is highly preventable or curable if polyps are detected early. (The cancer shows up first as one or more small polyps—growths of soft tissue—in the intestinal lining.) The polyps don't always turn cancerous, and people may have no idea the polyps are there, though sometimes these do cause symptoms such as bleeding, constipation, diarrhea, or cramps. Starting at age 50 everyone should undergo some kind of colorectal screening. Insurance will pay for some of the tests. But about 60% of eligible people have never had any kind of test. Many things discourage people from getting screened—embarrassment, for example. But not least is the confusion about which test to take. Doctors, too, are divided about which test to use.

Recently, amid lots of publicity, researchers reported that one test—colonoscopy—was more reliable for routine screening than the others. But this test is invasive and expensive. Insurance may not pay for it. What should you do to protect yourself against colon cancer? This list will help you review the options:

• Digital rectal exam. Because it is a quick, simple test, it is routine in most physicals (where it is also used to examine the prostate). But it can detect only about 10% of tumors.

• Fecal occult blood test (FOBT) is the simplest and cheapest test, except for digital rectal exam. Since many cancers of the colon and rectum bleed, FOBT is designed to detect hidden ("occult") blood in a stool sample. At home, you smear small samples on a card and mail it to a lab or doctor's office for analysis. This test will miss many precancerous polyps and some cancers, and it produces some false-positives. But it's still recommended by most authorities as a first step, and it has been shown to save lives. Insurance covers it.

• X-ray with barium enema examines the whole colon, and may be used following a positive FOBT. First, a barium enema is administered, and then the colon is inflated with air and X-rayed. It is useful but may miss smaller polyps. As a screening test, it is covered by insurance every 5 to 10 years for those 50 and older.

• Flexible sigmoidoscopy is an examination of the rectum and lower portion of the colon with a flexible, lighted tube. The test is very accurate, as far as it goes—only about one-third (two feet) of the colon's length. It can be done in a doctor's office; you take a laxative and/or enema in preparation; sedation is not needed. It can detect and remove polyps; a biopsy can then be done to see if they are precancerous or cancerous. As a screening test, it is covered by insurance starting at age 50 and every five years thereafter, which is the recommended frequency. But surprisingly few doctors offer the test to patients.

• Colonoscopy is a visual exam of the entire colon, via a flexible scope monitored on a video screen. It must be performed by a specially trained physician. You must take laxatives and eat no solid foods the day before, and you usually need sedation, as well as a few hours to recover. A highly accurate and valuable tool, colonoscopy can remove polyps that it detects. Complications, including perforation of the colon and hemorrhage, are rare but not unknown. The test is very expensive—up to $1,500. Most insurance covers it only for people who have symptoms, a strong family history, or inflammatory bowel disease (not to be confused with irritable bowel syndrome), or who have had abnormalities detected by the previously mentioned tests. Strong family history is defined as colorectal cancer or polyps in your mother, father, sister, or brother under age 60; or in two of these close relatives at any age.

Something called virtual colonoscopy is on the horizon. It's done via CT scans or MRI (magnetic resonance imaging). The colon has to be inflated for the procedure; it's less invasive than a colonoscopy, and may prove effective and less expensive. If anything shows up, you'll have to have a real colonoscopy.

So which is best?

Doctors used to think that if there were no polyps in the lower colon, there were unlikely to be any further on—and thus sigmoidoscopy would be an adequate test. It's becoming evident that many cancers occur beyond the reach of the sigmoidoscope, with no sign in the lower colon that anything is amiss. In July two well-designed studies in the New England Journal of Medicine found that about half of people diagnosed with cancer of the upper colon via colonoscopy showed no sign of it in the lower colon. Sigmoidoscopy would not have found these cancers. In an editorial in the same issue, Dr. Daniel Podolsky of the Massachusetts General Hospital in Boston advocated colonoscopies for everybody 50 and over.

Counting the cost

This has given rise to a heated debate among the experts. If Medicare and other insurers agree to cover screening colonoscopies for everybody over 50, premiums are certain to rise—never a pleasant prospect for taxpayers, employers, or insurers. Congress is working on legislation to expand Medicare coverage of screening colonoscopy, but there's no certainty that it will pass. (In addition, one state, Virginia, requires insurance to pay for screening colonoscopies starting at age 50.) But even if cost were not an issue, there's another problem: there wouldn't be enough specialists to do colonoscopies if most people over 50 wanted one.

What to do

If you are at high risk for colon cancer (that is, if you have a strong family history, inflammatory bowel disease, or have had pre-cancerous polyps removed already), you should undergo colonoscopy periodically according to your physician's advice. Insurance does cover colonoscopies for high-risk people, but "high-risk" may not include everyone with a family history.

If your only known risk factor is being over 50 and you have no symptoms, where does this leave you? About 75% of colon cancers occur in people who are not at high risk. If no one in your family has had the disease, that doesn't mean you won't get it. All of the tests are worth doing—they not only are able to detect colon cancer early, when it can be successfully treated, but often are even able to prevent it.

• At a minimum, ask your doctor for a fecal blood test annually and a sigmoidoscopy every five years. Together, these methods will detect most colon cancers: they offer substantial protection and save thousands of lives. Insurance covers both tests.

• But also talk with your doctor about colonoscopy. It requires more preparation and a longer recovery time than sigmoidoscopy, and poses a greater risk of complications. If you can afford to pay for a colonoscopy, you may decide that the added benefit is worth the money and risk. You need it only once every 10 years if the results are normal—so if it costs $1,500, that works out to only $150 a year. If you can't afford that, the combination of fecal blood test and sigmoidoscopy is still an excellent option.

UC Berkeley Wellness Letter, December 2000