Don't be afraid of colorectal cancer screening

Screening tests: what do they entail?

Not all the screening tests for colorectal cancer are invasive. Basically, these tests are designed to detect fingerlike projections of tissue, called polyps, in your colon and rectum. Polyps may be cancerous or precancerous. Although most polyps are not cancerous, the majority of colorectal cancers develop within polyps.

Here's what's involved with each test:

Fecal occult blood test – a test for hidden blood in a sample of stool (feces) you have already passed. Blood in your feces may be the result of bleeding from a cancerous polyp in your colon or rectum, or it may be a sign of a more benign condition.

Flexible sigmoidoscopy – a thin, lighted tube inserted into your rectum to examine the rectum and the lower colon. The lighted tube displays a picture of the inside of your rectum and lower colon so the doctor can look through an eyepiece for polyps.

Colonoscopy – a thin, lighted tube inserted through your rectum and into your colon to examine the lining of the entire colon. This time, the lighted tube goes all the way into your colon and displays a picture so the doctor can look through the eyepiece for polyps. Polyps that are detected can be removed during the same procedure.

Digital rectal exam – use of the doctor's gloved finger to feel for polyps inside of your rectum.

Double-contrast barium enema – injection of fluid into your rectum that makes your colon show up on an x-ray to help doctors see abnormal growths in your colon.

Screening recommendations

The American Cancer Society suggests that starting at age 50, men and women should be screened for colorectal cancer with one of the following options:

• Yearly fecal occult blood test (preferably the take-home, multiple sample method); or
• Flexible sigmoidoscopy every 5 years; or
• Fecal occult blood test every year and flexible sigmoidoscopy every 5 years; or
• Double-contrast barium enema every 5 years; or
• Colonoscopy every 10 years

However, people at increased risk of colorectal cancer may need to have some of these tests earlier in life and more often. You're considered to be at increased risk if you have:

• Personal or family history of colorectal cancer or adenomatous polyps
• Personal history of chronic inflammatory bowel disease, such as ulcerative colitis or Crohn's disease
• Personal or family history of other types of cancer, such as those involving the breast, ovary, uterus, and other organs

Screening controversy

Colonoscopy can undoubtedly detect and remove precancerous polyps in the colon and rectum. And it has been proven that a good percentage of people who have no polyps in the rectum and lower colon (where sigmoidoscopy reaches) do have polyps farther up in the colon. So colonoscopy is more likely to find polyps and tumors than all of the other tests.

But here's the controversy. Some of these tests have been shown to help prevent deaths from colorectal cancer and others have not. And they may not be the ones you'd expect.

Digital rectal exam is a simple test, but not very effective at detecting polyps. Studies show that, though barium enema is effective at detecting larger polyps, it is a less effective screening tool than colonoscopy. Scientific research has shown that annual or biennial fecal occult blood tests in people aged 50 to 80 decreases the number of people who die from colorectal cancer. However, the scientific evidence for sigmoidoscopy is less clear. As of January 2002, the National Cancer Institute reports that regular sigmoidoscopy in people over age 50 may decrease deaths from colorectal cancer, but there is insufficient evidence to determine how often people should undergo sigmoidoscopy. As for colonoscopy, there is currently no evidence that universal screening via colonoscopy would save lives. On the other hand, one-half of people who have polyps or tumors in the upper part of the colon, where only a colonoscopy reaches, have no polyps or tumors in the lower colon, where the sigmoidoscopy reaches. According to statistics from the National Cancer Institute, limiting colonoscopic screening to only high-risk people would miss the majority of colorectal cancers.

It certainly makes sense that scanning the colon and rectum for polyps and removing them would reduce your risk of developing colorectal cancer. But more research is needed to determine which tests actually save lives and how often you need to have those tests.

What tests do you need?

How do you know what screening tests you need and when, if the experts can't seem to agree? For starters, you need to have the yearly fecal occult blood test starting at age 50, unless you have one of the more invasive tests instead. Your doctor will assess your risk of colorectal cancer and recommend further tests, such as sigmoidoscopy or colonoscopy, if necessary. Don't be afraid to have one of these tests if your doctor recommends it. As Katie Couric showed the world, it really doesn't hurt (though it can cause some gas, bloating, or abdominal cramps)...but it could save your life.