Colorectal cancer is the second leading cancer killer of Canadians. It is second only to lung cancer as a cause of cancer related deaths. This cancer, also called bowel cancer, affects the large intestine and rectum. More deaths come from this disease than either breast or prostate cancer.
The good news is that a simple screening test can reduce deaths from this disease. The bad news is that few of us are using it. Only about 20 per cent of Canadians in the target age group report being up-to-date on colorectal screening. Yet for Canadians over 50, simply adding this test to health check-ups would effectively lower the number of deaths.
Several tests can be involved in screening for colorectal cancer. The simplest is the fecal occult blood test, or FOBT. This test examines feces (stool, or as kids would call it, poop) for occult blood. Blood may be present in such small amounts that it cannot be seen by the naked eye. This test has the most research behind it as a test for normal healthy adults.
The FOBT is valuable because most colorectal cancers start as benign (not cancerous) polyps. Polyps are small growths inside the large intestine. Some might remain benign polyps forever, if left alone. Others, after several years, could develop into cancer. As they grow, many of these polyps bleed small amounts of blood – and so do early cancers.
The idea is to find these growths early through telltale microscopic bleeding. With testing, they are discovered well before bleeding becomes heavy enough to be easily seen, or other later systems of bowel blockage appear.
International studies have shown that using this test every one or two years on people over age 50 lowers the death rate by about 25 to 30 per cent. (Colorectal cancer is found more often in those over 50.) The test also reduces the number of new cancers, probably by finding and removing early pre-cancerous polyps.
All that is needed are very small samples of stool, taken on three separate days, which are then sent to a lab for analysis. You may be asked to avoid red meat (as it may contain small amounts of blood), and alcohol, vitamin C, ASA (Aspirin™) or other drugs that might cause minor intestinal bleeding for a few days before and on the actual test days. Other tests have found that this amount of restriction is not necessary and only limit vitamin C use. Just follow the instructions. If you cannot do without the medications, discuss it with your doctor. Either way, there is not a great deal of preparation.
On the day of the test, you use a disposable pan when having a bowel movement. A small stick or brush is supplied to put a small amount of stool on filter paper or into a tube. You then close the test paper cover or tube, and put your identification on it. That is all.
Using stool as material for a lab test may seem a bit strange at first, but as screening tests go, this one is pretty simple.
If the test is positive, which happens about two to five per cent of the time, it certainly does not mean that you have cancer. However, it does mean that you need further testing, Colonoscopy, also used for diagnosis in international studies, is the next recommended test.
In a colonoscopy, a tube with a scope is inserted into the colon via the rectum. The trained professional doing the test can see directly whether there are polyps or signs of disease. If polyps exist, it is often possible to remove them during the colonoscopy procedure.
More preparation is necessary for a colonoscopy. The colon must be clean so that the surface can be seen. You will take a solution the day before the test to ‘clean out’ the bowel. This is not a good day to be far from the toilet!
On the day of the test, you may be given a mild sedative to help you relax during the test. If so, you will need to be driven home by a friend or family member.
The test itself is not usually too unpleasant. Several celebrities, such as Katie Couric, have even had it done while being televised, so that they can demonstrate how straightforward it is.
If the test is normal, no further follow-up is usually required. However, your doctor may recommend additional monitoring. If a polyp or other growth is found, it may be removed and sent for further examination. If cancer is found, you will be referred for surgery and other treatment.
Even if cancer is diagnosed, you are much more likely to do well if it is found through early screening rather than at a later stage. Treatment is also likely to be less aggressive.
Are there any controversies or downsides?
No screening test finds every cancer, and the FOBT is no different. It is often recommended that the test be done annually. If a polyp or cancer is not picked up on the first set of tests, it may be noticed on the next round. Since the lead time for the change from polyp to cancer is very long, yearly testing helps reduce deaths from this disease.
While colonoscopy is a safe test, it is not totally without risk. Bleeding and perforation (a hole made in the bowel) can occur, although rarely. Talk to your family doctor or other primary care provider before having a colonoscopy, so that you understand all of the benefits and risks.
As with most medicine, and certainly with screening tests, controversy exists about the best way to screen for colorectal cancer. The FOBT is the recommended screening tool in most programs around the world. It has scientific evidence to back it.
Some believe that offering colonoscopy as the screening test would be more efficient. However, colonoscopy is not without risk. Others say it should only be offered to those at higher risk – such as those with a family history of colorectal cancer or a positive FOBT.
In Canada today, as in most of the world, we simply do not have the capacity to offer colonoscopy as the primary screening test to the whole population. We will best help the total population by using the FOBT for as many people over age 50 as we can reach. Then, we can make certain that colonoscopies are rapidly made available to those with a positive test result. This strategy is also being used in the United Kingdom and Australia.
Two other tests could help our ability to find colorectal cancer early. Flexible sigmoidoscopy uses a shorter scope and requires less professional training to use. Studies are underway in the UK to see whether this tool could be used to screen along with FOBT.
‘Virtual colonoscopy’ is a computerized tomography (X-ray based) test. The advantage is that inserting a scope is not necessary to develop a picture of the colon. However, if abnormalities are seen, a colonoscopy would still be necessary.
Both tests are under investigation. Both require the same type of preparation as with a colonoscopy. While they are available in Canada, they are not widely used as screening tests.
In Alberta and Manitoba, colorectal screening programs have been launched. British Columbia and Saskatchewan will introduce them soon. Such programs will help make the FOBT test widely available and understood, and ensure that those needing follow-up receive it quickly. They will also reduce the number of Canadians who develop and die from colorectal cancer.
If you or someone you know is over 50, the first step is to talk to your family doctor or primary care provider about colorectal cancer screening. Your family doctor will likely have suggested it as part of your periodic health assessment.
If you feel embarrassed to talk about it, remember that we used to be shy about breast screening too. Part of our success in lowering breast cancer deaths happened because people began talking about it. When women became aware of the risk, they better understood the benefits of breast cancer screening.
So, stretch your sense of humour and start talking about poop – it is likely to be a lively conversation. It may even save a life!