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ColonCancerCheck is a "new" program being rolled out by the Ontario government. I have been fielding a lot of questions about this supposed "new" test. Bowel cancer has had a profound effect on my career and family, and bowel cancer ranks in second place as a cause of cancer deaths. Prevention and early detection are key concepts in dealing with bowel malignancies. There is a lot of publicity surrounding the new endeavors to provide Ontario residents aged 50-74 with bowel screening.
There is nothing new about the test itself. It is an old test in new packaging. This "technology" has been around for decades and is based on a simple chemical principle. Blood contains hemoglobin, which being a protein, can act as an enzyme. To take advantage of this principle, a sheet of paper is pre-treated by immersion in a solution of guaianoc acid. Stool, which may contain hemoglobin rich blood, is smeared on the paper. A drop of strong base such as hydrogen peroxide is placed on the smear. The peroxidase in the hemoglobin will catalyze oxidation of the guaiaconic acid in the paper to form a blue compound. Practically speaking, you perform this new self-test by smearing a small amount of stool on the special paper slide. You then label it and seal the special stool-smeared paper into an envelope and mail it to the government assigned laboratory. What could be more fun? It is just like doing your tax return. A lab will process it by adding a drop of hydrogen peroxide and look for the blue color to appear. Your doctor and you will be notified if this happens. In this regard, it really is not a bowel cancer test, but a non-specific test for blood detection.
The current initiative is aimed at identifying more people to add to the screening process. People with early family histories and over the age 50 who have a positive test are sent to obtain a colonoscopy. This is a camera guided tour of your colon. There have been waiting lists to obtain this test, which is the current gold standard. Expansion of current facilities has greatly helped, but providing everyone over 50 with a colonoscopy would be impossible.
A positive test does not mean that you have bowel cancer. It simply suggests that there may be some microscopic blood in your stool. But it could also mean that you ingested other compounds such as red meat, beets or vitamin C. Your bowels are a living organ. Aggravating them by using anti-inflammatories such as aspirin can cause trace amounts of non-cancer bleeding. Similarly, diseases such as colitis can do the same. Bleeding from other causes such as hemorrhoids, urine infections and menstruation can also turn the test positive. But sometimes, small precancerous bowel polyps can bleed as do growing cancer lesions.
One paradox of this system is that a negative test actually hinders your chance for colonoscopy. Some of my patients are savvy enough to do their own research. There are stool tests in existence that use the latest DNA technology to look for genetic mutations in cells that are regularly sloughed off the intestinal walls. Colorectal cancers tend to involve mutations of genes, APC, K-ras and p53 being common ones. It is possible to detect early stages of bowel cancer using this alternate technology, but the testing is more expensive and not a routine part of our health system.
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