Don’t Be Afraid of Colorectal Cancer Screening
Posted on 3/27/2003
Just talking about a colonoscopy makes most people cringe. That’s probably because the idea of having a tube inserted into your rectum and colon is disturbing.
But even more disturbing for many people is the thought of getting colorectal cancer. Colorectal cancer is the second deadliest cancer in the U.S. and the third deadliest cancer worldwide. But when diagnosed at an early stage, before the cancer has invaded the colon wall or spread to distant sites, the chances of survival are much higher.
Still, by definition, all screening tests are performed on people who feel fine except for the anxiety they have about their future health. And while some screening tests clearly decrease the risk of dying, that is certainly not true of all of them.
What about colorectal screening? Is the unpleasant prospect of having a colonoscopy or some other equally disagreeable procedure really worth it? For many of us, the answer is “yes”.
Screening Tests: What Do They Entail?
All colorectal screening tests are designed to detect, either directly or indirectly, fingerlike projections of tissue, called polyps, in your colon and rectum. Polyps may be cancerous or precancerous. Although most polyps are not cancerous, the vast majority of colorectal cancers are believed to begin as polyps. Fortunately, not all the screening tests for colorectal cancer are invasive.
Here’s what’s involved with each test:
Fecal Occult Blood Test
The fecal occult blood test is 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
For a flexible sigmoidoscopy, a thin, lighted tube is inserted into the rectum and lower colon to examine their internal mucosal lining. Images can be recorded on a video tape while the doctor looks for polyps and other abnormalities through an eyepiece.
Colonoscopy
For a colonoscopy, a thin, lighted tube similar to a flexible sigmoidoscope, only much lighter, is used. This time, the lighted tube goes all the way through to the end of your colon where it connects to the small intestine. Polyps that are detected can be removed during the same procedure.
Digital Rectal Exam
A digital rectal exam involves the insertion of a lubricated, gloved finger into the rectum to check for lumps, polyps, or other abnormalities inside of the rectum.
Double-contrast Barium Enema
A double-contrast barium enema involves the injection of a fluid called barium followed by air into your rectum. This makes your entire colon visible on an x-ray, allowing doctors to see abnormal growths, like polyps.
Computed Tomography (CT) Colography
Computed tomography colography is a new technique that takes computer generated x-ray images after injection of air into the colon. It provides more details of the mucosal lining than double-contrast barium enema, but its clinical usefulness is not clear.
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 any of the following:
- 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 throughout the colon and rectum. And since some people who have no polyps in the rectum and lower colon (where sigmoidoscopy reaches) turn out to have them farther up, colonoscopy is more likely to find polyps and tumors than any 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. Although barium enema is effective at detecting larger polyps throughout the colon, studies have shown that it is a less effective screening tool than colonoscopy. There is evidence that annual or biennial fecal occult blood tests in people aged 50 to 80 decreases the risk of dying from colorectal cancer. However, since many other problems produce blood in the colon, a lot of people end up having false positive results. Having the test every two years instead of annually can reduce this risk.
The US Preventive Services Task Force recently determined that regular sigmoidoscopy alone or in combination with FOBT reduces colorectal mortality. There is insufficient evidence, however, to know exactly how often people should undergo sigmoidoscopy, although many authorities say every five years is probably reasonable.
As for colonoscopy, there is currently no evidence that screening everyone irrespective of their risk would save lives. Although colonoscopy is considered generally safe, it is more risky than any other colorectal screening test and far more expensive. 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. This means that many patients who only undergo sigmoidoscopy will have polyps missed.
What Tests Do You Need?
While it now seems clear that screening for colorectal cancer after age 50 in average risk individuals is better than not screening at all, the best combination of screening tests and their frequency has yet to be determined. So, how do you know what screening tests you need and when?
For starters, you ought to at least have the yearly fecal occult blood test starting at age 50, and you should probably consider having a sigmoidoscopy at least every five years, since most of the evidence indicates that these tests save lives. Talk to your doctor about the advantages and disadvantages of a full colonoscopy, especially if your risk for colorectal cancer is greater than average. Few would argue that it’s the most attractive option, but it may save your life.
by Laurie LaRusso, MS, ELS
RESOURCES:
American Cancer Society
http://www.cancer.org/
National Cancer Institute
National Institutes of Health
http://www.nci.nih.gov/
SOURCES:
National Cancer Institute
http://www.nci.nih.gov/
American Cancer Society
http://www.cancer.org/
Centers for Disease Control and Prevention
http://www.cdc.gov/
National Institute of Diabetes & Digestive & Kidney Diseases
http://www.niddk.nih.gov/
American Gastroenterological Association
http://www.gastro.org/
U.S. Preventive Services Task Force
http://www.ahcpr.gov