Are you at risk?
There is no universal set of screening guidelines, and doctors consider recommendations from a number of organizations, such as the Canadian Association of Gastroenterology and the Canadian Digestive Health Foundation. Reviewing your family history with your doctor is important in assessing the risk of colorectal cancer, says Dr. Desmond Leddin, professor of medicine at Dalhousie University and head of the division of gastroenterology at Queen Elizabeth II Health Sciences Centre in Halifax.
People at average risk include those over 50 who have no close relative with colorectal cancer, and much of the population falls into this category. “There are other people who are at increased risk,” he adds. “The main risk factor is having a close relative who has colon cancer, and the concern is that may indicate there is a genetic predisposition. If you have a close relative, especially a brother, sister, child or parent, who had colon cancer under the age of 50, there may be a genetic factor at work.” Other risk factors include a previous history of polyps, poor diet, pre-existing inflammatory bowel disease or Crohn’s disease.
People with a history of inflammatory bowel disease or benign polyps may also have a higher-than-average risk. But about 70 to 75 per cent of colorectal cancers occur in people who have no specific risk factors, according to the Canadian Cancer Society.
After your family doctor assesses your risk, Leddin suggests you talk about the screening options available in your area.
Fecal Occult Blood Test. The FOBT checks stool samples for traces of blood not visible to the naked eye. Usually, you get the testing kit and instructions from your family doctor and send the samples to a lab when you are finished. For a few days before testing, you have to avoid certain foods and medications (such as red meat, raw vegetables and ASA) to help reduce false positive results.
Pros and cons: This relatively easy and inexpensive test can be used for screening large numbers of people. “For average risk, it is the only method that is really feasible on a population basis,” says Leddin. “The disadvantage is that it’s not particularly sensitive. It misses a fair number of tumours and, perhaps even more importantly, it’s very poor at picking up precancerous polyps. It’s not really so much a prevention strategy as it is an early warning system that there is a cancer.”
Blood in the stool can also be as a result of non-cancerous conditions, such as hemorrhoids or anal tears, so follow-up for a positive test generally includes one of the other screening tests to examine the colon.
Colonoscopy. A doctor inserts a thin, flexible tube with a tiny camera at the tip into the colon. The object is to find and remove polyps, tumours or samples of abnormal tissue to check for cancer. The doctor performing the test is a gastroenterologist or general surgeon. You usually have the procedure in a hospital on an outpatient basis or at a specialist’s clinic under light sedation to reduce discomfort. To clean out your colon before the test, you need to follow a special diet and take laxatives for a day or two.