Tests related to colon cancer

There are three basic tests that I know of, in addition to at least three types of examinations.

1. Hemoccult test--this one has been around for a while. It is a take-home test, sometimes availale from your pharmacist or the American Cancer Society. The test is free. The test kit consists of three pieces of filter paper, on which you smear three small stool samples, taken at different times. You send the kit in for analysis and receive results by mail. The test looks for occult (hidden) blood, which may have come from a cancer in the colon. Since there are a number of other reasons to have blood in your stool (hemorroids for example). A positive test result simply means there is more testing to do.

2. The test I described a couple of days ago is a genetic test for the existance of cancer. Some colon cancers are associated with one or more of three genetic mutations. The test, which you can purchase over the Internet, looks for these mutations in cells within a stool sample. I believe the test is quite expensive. If you think you'd like to try this test, I would recommend consulting a physician. Insurance is more likely to cover the test that way.

3. Another test is a predictive test: do you have the genetic mutation that results in more frequent polyp formation in the colon? Approximately 5-10 percent of colon cancers are associated with this mutation and as many as 80 percent of people with this mutation may develop colon cancer. This test is also available over the Internet, but I recommend a physician's support is here also.

Then, there are the "physical" exams: sigmoidoscopy and colonoscopy. In both cases, the preparation for the exams is worse than the exam itself. If you are over 50, you should have the colonoscopy at least every 10 years, more often if you have a tendency to form polyps or a family history of forming polyps. A sigmoidoscopy is generally less extensive than a colonoscopy; to me there's no logical reason to do the lesser of the exams. I believe it was more popular when exams were done without a sedative and were often painful. The colonoscopy is performed when you are sedated and the physician performing the exam can take photographs/videos for comparison with later tests. If polyps are found during the exam, they can be removed and tested for malignancy. The prep? You have to clean out the colon for the examination. This means drinking a fluid to stimulate evacuation and staying near a bathroom.

The third test is a "virtual" colonoscopy. I believe it involves getting a miniature camera into the colon--by swallowing a gelatin-coated pill--and then picking up the transmissions from the camera. I'll have to check this one out further, because I haven't heard much about it lately, and don't know if it's still being used, and if it is, how the whole process works.

To learn more about any of these tests, check out the American Cancer Society's site. Remember that the organization is somewhat conservative and generaly recommends only the most tested exams, not listing newly developed tests or exams until they have been clearly shown to benefit people.

If you have a specific question about a test or exam, or about the genetics of colon cancer, please use the comment mode to ask your question. You do not have to give your name.

Marie Godfrey, PhD