Colon Cancer - Prevention and Screening
Section titled “Colon Cancer - Prevention and Screening”In last month's newsletter, we discussed living life to the full, as opposed to trying to live forever. One symptom of the desire to live forever is the common medical recommendation that everyone over the age of fifty should have a colonoscopy. In this procedure, a surgeon inserts a fiber optic tube into the rectum and threads it through the length of the colon. A camera at the end of the tube projects pictures of the inner colon onto a screen, enabling the surgeon to scout for and remove pre-cancerous growths.
Important point! The following is an assessment of screening, which means looking at people who have no symptoms! If your doctor recommends colonoscopy for the evaluation of symptoms, that is a diagnostic colonoscopy. Different animal!
The Argument for Screening
Section titled “The Argument for Screening”Colon cancer begins as a fleshy finger-shaped growth into the colon called a polyp, which can be identified and removed with a fiber-optic tube up the wazoo. Then, just as with skin cancer, it is gone forever. If not removed, these cancerous growths invade the colonic wall and will often spread to distant organs before causing symptoms such as blood in the stool and abdominal pain. One in 17 Americans dies of colon cancer and 80 percent of those people have no risk factors. Therefore, the reasoning goes, everyone should have this test at least once every ten years.
What They Don't Tell You
Section titled “What They Don't Tell You”1. Colonoscopy identifies 94 percent of colonic polyps. Polyps smaller than a cranberry are considered less dangerous; colonoscopy misses about 20 percent of those. You can see a picture of a polyp at http://digestive.niddk.nih.gov/ddiseases/pubs/colonpolyps_ez/. Most polyps are benign, but some become cancerous.
2. Colonoscopy requires about 30 hours of time, including initial visit with the physician, laxative treatment to empty the colon, the procedure itself, and recovering from the sedatives used during the procedure.
3. The cost ranges from $1300 to $2000.
4. For every 330 people who have a colonoscopy, one will have a significant problem, either bleeding requiring surgery, heart attack, stroke, or other blood clot. About one in 10,000 will die.
5. Per year of life saved, colonoscopy screening costs $10,000 to $25,000.
6. Intelligent estimates are that colonoscopy can prevent 70 to 90 percent of colon cancer deaths. However, there is no definite proof. We really don't know if screening colonoscopy provides the best benefit for the costs involved. Read on and I'll tell you why.
As we discussed with mammography in our April 2005 newsletter, the value of cancer screening is easily overestimated. Screening tends to identify more slow-growing and less aggressive cancers.
Screening colonoscopy can give us the illusion that we are protected more than we are. How can we achieve maximum protection from colon cancer? The first step is to be aware that there is NO - I repeat, NO - method of sure-fire prevention. All you can do is to reduce the odds. Let's talk about how we can achieve that.
Lifestyle for Prevention
Section titled “Lifestyle for Prevention”You can live in such a way as to lessen your risk of colon cancer.
- Eat a diet rich in fiber, fruits and vegetables. This is the diet of pre-industrialized peoples, who have less colon cancer than we do.
- Be sure that you get nutrients such as omega-3 fatty acids, vitamins D, and E, beta-carotene and calcium, all of which reduce risk.
- Eat folic acid-rich food or take folic acid supplements. Folic acid alone, all by itself, can reduce your risk of developing colon cancer by about half. See our article on Folic Acid in the December 2004 issue of the newsletter. More folic acid is more protective. I suggest 5 milligrams (5000 micrograms) daily with B complex to back it up.
- People who exercise the most get colon cancer at only 60 percent the rate of those who exercise least.
Choice of Tests
Section titled “Choice of Tests”If you have a small cancer already cooking in your colon, starting preventive measures now won't help. If you haven't been doing these things for ten years, you can't consider yourself at low risk. You need to think about colon cancer screening. Here's how:
In order of importance, let's look at tests other than colonoscopy, which are used for colon cancer screening.
Microscopic blood in stool - FOBT
Section titled “Microscopic blood in stool - FOBT”What is it? - The medical name for this test is the "fecal occult blood test" abbreviated FOBT. This "card test" identifies blood in the stool before it becomes visible. People take a set of cards home with them, place stool samples on the cards, and return them to the office. We process the cards to determine if microscopic amounts of blood are in the stool. If so, we strongly recommend a colonoscopy to determine the source of the blood, which can come from food, hemorrhoids, ulcers, polyps, intestinal inflammation, or colon cancer.
How Effective? - For people at average risk, it is a cost-effective screening test. When used yearly by a study group of 46,000 people, it reduced the risk of death from colon cancer by about 20 percent. It does not identify everyone with cancer.
Cost - We currently use the most accurate of these tests, the Hemoccult Sensa II™, which costs $12.
Disadvantages - The problem with the card test is that people are reluctant to collect and return the samples. For example, in the study mentioned above, only half the participants used the test as directed. Had they used the test as directed, the risk of death from colon cancer would have been reduced by much more than 20 percent. If the test is positive, you will then need a colonoscopy.
InSure™
Section titled “InSure™”What is it? - A newer generation of stool test detects cancer more surely and is also easier to collect.
How Effective? - There are no long term studies, but early indications are that it detects about 90 percent of cancers and reduces mortality by 80 percent IF USED EVERY YEAR.
Cost - $90
Disadvantage - Two percent of people using this test will have falsely positive results. If the test is positive, you will then need a colonoscopy.
Flexible sigmoidoscopy
Section titled “Flexible sigmoidoscopy”What is it? - This is similar to a colonoscopy but examines only the lower third of the colon.
How Effective - This is believed to be the least cost-effective of the three major screening methods (colonoscopy and FOBT being the other two)
Cost - Base cost is $220. If the surgeon finds and removes a polyp, the cost rises to $485.
CT scan (also called virtual colonoscopy)
Section titled “CT scan (also called virtual colonoscopy)”What is it? - CT scanning is still under development. Results vary wildly depending on skill and technique. I would avoid anyone outside of a major medical center who offers this test.
Carcinoembryonic antigen - CEA
Section titled “Carcinoembryonic antigen - CEA”What is it? - Blood levels of CEA rise with advanced cancer, but the test doesn't adequately distinguish normal people from those with early cancer.
What is it? - DNA from cancer appears in the stool. How Effective - DNA testing is only about 65 percent sensitive. Cost - $650.
Videocapsule
Section titled “Videocapsule”What is it? - A camera in a small capsule is swallowed. This test isn't ready for prime time.
Double-contrast barium enema
Section titled “Double-contrast barium enema”What is it? - Air and barium are instilled into the colon and an X-ray examination is performed. Risk is low (1 death per 50,000 procedures).
How effective is it? - This test finds only half of the polyps found on colonoscopy.
Cost - About $600 to $700.
The Official Recommendations
Section titled “The Official Recommendations”The American Cancer Society and the American Gastroenterology Association recommend that people of average risk for colon cancer have a screening colonoscopy every ten years beginning at age 50. A recent review of colon cancer screening in the journal Medical Clinics of North America (Jan 2005, 89:54) concluded that no method of screening is widely enough used and that careful application of FOBT or colonoscopy "will result in a decline in colorectal cancer incidence and mortality."
If you ask your doctor, the answer you are most likely to get is to go ahead and get the colonoscopy. The reason is that your doctor knows that one in twenty Americans is going to get colon cancer at some point in their lifetime. If that question and answer ever gets into a courtroom, there is only one right answer. It has nothing to do with sensitivity, specificity, cost-effectiveness, and adverse effects of testing.
How do I choose?
Section titled “How do I choose?”If you have a parent or sibling who developed colon cancer or adenoma (an adenoma is a kind of polyp) at any age, particularly at age less than 60, regular screening with colonoscopy is in order. You need a colonoscopy beginning at age 40 or even earlier if you have a relative who developed it under the age of 50.
Otherwise, you need to weigh your own situation. Look at your risk factors. In order of severity, risk factors are advancing age, certain colonic diseases, high red meat diet, pelvic irradiation, high fat diet, tobacco and alcohol use, obesity, and having had gall-bladder surgery.
Consider your protective factors, too. These are
- Those listed above under "Lifestyle for Prevention,"
- Blood Selenium Level - Men with a selenium level less than the median of 128 micrograms per liter have four times the risk of colonic polyps.
- Aspirin - If you take aspirin 16 or more times a month, you have only 60 percent the risk of cancer of those who take none. Other NSAIDS (non-steroidal anti-inflammatory drugs such as ibuprofen) are protective, too. However, aspirin may have side effects. See our article in the October, 2004 issue of our newsletter,
- Estrogen replacement therapy - This cuts risk of colon cancer to 70 percent of normal, but of course may cause side effects of its own. See our article on estrogen in the July, 2002 issue of the newsletter.
If you weigh these factors (and you can ask your doctor for help) and believe yourself to be at above-average risk, you are better off with a colonoscopy. If you are at average risk or better, get an annual test for hidden blood in the stool. Use the Hemoccult Sensa II™ or the InSure™ test. "Annual" means Every Year. If you are a Once in a While person, then you are better off with a colonoscopy.
Most important -- start that Preventive Lifestyle today. In ten years you can thank yourself, because you will have reduced your colorectal cancer risk to less than 25 percent of normal and a screening colonoscopy will be out of the question.
Checking the Facts
Section titled “Checking the Facts”As always, I invite you to check my facts. A useful source of information is the National Library of Medicine at http://gateway.nlm.nih.gov/. There are thousands of research studies on this subject, and each shows something different. My conclusions above are based on my synthesis of much, sometimes conflicting, information and research.
CJK May 10, 2006