Colon cancer is a disease in which cancerous cells form in the wall of the large intestine (colon) – the part of your digestive system that absorbs water and turns food waste into stool.
Here’s how it usually starts: the cells that line the colon can sometimes become abnormal and start to divide rapidly, forming benign growths called polyps
Caused by a mix of genetic and environmental factors, colon cancer can affect people of all ages, but is most common after age 50. While most colon cancers are not hereditary, you may have a genetic susceptibility if several of your relatives have been affected or if they got the disease before age 60.
Every year, about 23,000 Canadians are diagnosed with colon cancer and 9,000 will die of the disease. This makes colon cancer the third-most common cancer – behind prostate and breast cancer – and second-most common cause of cancer deaths in the country. For this reason everyone should participate in a provincial/territorial colon cancer screening program as soon as you turn 50 or earlier if your risk profile suggests an earlier start. Such a program ensures you’ll be tested and retested at the appropriate intervals and could save your life.
Good communication with your doctor is an important part of managing your digestive health, regardless of your diagnosis.
More than 90 per cent of colon cancer cases occur in people over 50, which makes age the biggest risk factor for the disease. Because many people experience no symptoms in the early stages of the disease, the Canadian Digestive Health Foundation recommends that all people over 50 get screened. You should also get screened if you have other risk factors that make you more likely to get the disease.
Most colon cancers arise from polyps. These are small growths within the colon that usually do not cause any symptoms. The good news is, preventing colon cancer is possible through regular screening.
They appear as small bulges from the bowel wall (much like a mushroom protrudes from the ground). Over time the polyps will grow and, under appropriate conditions, turn into colon cancer.
If detected early, polyps can be easily removed through colonoscopy, thereby eliminating the polyps and their risk. Since colon cancer typically arises from colonic polyps, and since polyps do not lead to symptoms, early testing may help to detect and remove polyps and prevent progressive disease.
It is important for patients at risk to be checked early to prevent cancer from developing. Once your turn 50 years of age, it's a good idea to talk to your doctor about regular screening to prevent polyps from growing.
In addition to appropriate screening, there is convincing evidence that diets low in fat and meat and higher in fruits and vegetables can help in preventing colon cancer. Eating whole rather than processed wheat may also help reduce your risk, along with getting enough Vitamin D. Health Canada recommends that everyone over 50 take 400 units of Vitamin D per day (unless there is a reason not to). Some experts also recommend taking folic acid unless someone in your family has had polyps or cancer.
Some statistics on colon cancer:
Canadian Cancer Society’s Advisory Committee on Cancer Statistics. Canadian Cancer Statistics 2017. Toronto, ON: Canadian Cancer Society; 2017. http://www.cancer.ca/~/media/cancer.ca/CW/cancer%20information/cancer%20101/Canadian%20cancer%20statistics/Canadian-Cancer-Statistics-2017-EN.pdf?la=en [accessed 3 September 2018]
Canadian Cancer Statistics Advisory Committee. Canadian Cancer Statistics 2018. Toronto, ON: Canadian Cancer Society; 2018. http://www.cancer.ca/~/media/cancer.ca/CW/cancer%20information/cancer%20101/Canadian%20cancer%20statistics/Canadian-Cancer-Statistics-2018-EN.pdf?la=en [accessed 3 September 2018]
Canadian Digestive Health Foundation. 2009. Establishing digestive health as a priority for Canadians. The Canadian Digestive Health Foundation – National Digestive Disorders Prevalence & Impact Study Report. Public Health Agency of Canada. 2017. Colorectal cancer. https://www.canada.ca/en/public-health/services/chronic-diseases/cancer/colorectal-cancer.html [accessed 3 September 2018]
Most colon cancer is detected through routine screening, though you need a doctor to make an official diagnosis. The signs and symptoms of colon cancer listed below and on the next page may indicate colon cancer – though they often don’t – so it’s important to see your doctor right away if you have any of them. Your doctor can then decide if you need to have any tests. In most cases, there are no signs and symptoms of colon cancer especially in the early stages of the disease. When symptoms do occur, they may include:
A risk factor is something that makes you more likely than average to develop a condition. Ask yourself the following:
If you answered yes to some of these questions, you may have a higher-than-average risk of developing colon cancer and should speak to your doctor about screening. Keep an especially close eye out for the signs and symptoms of colon cancer.
While each province/territory has its own screening recommendations, common screening tests include: Stool Tests
You collect samples from three separate bowel movements and mail them to a laboratory where the samples are analyzed for traces of blood not visible to the naked eye. If you have a positive result – which doesn’t necessarily signal cancer – you will be referred for a colonoscopy.
This newer test, which yields more accurate results than FOBT and requires only one fecal sample, is replacing FOBT in many provinces.
Recommended frequency with FOBT (either gFOBT or FIT)Adults aged 60 to 74 - every two yearsAdults aged 50 to 59 - every two years
This test uses a lighted, flexible instrument called a sigmoidoscope to examine the sigmoid colon (lower part of the colon) and rectum. Recommended frequency: every 10 years.
This is the most sensitive of all colon cancer tests. You’ll probably be under sedation while your doctor carries out this safe procedure which uses a lighted, flexible tube called an endoscope to examine the entire colon. The tube is inserted into the anus and rectum and carefully guided up through the colon. Recommended frequency: every 10 years for people at average risk of colon cancer.
The procedure usually takes 20 to 30 minutes, but can occasionally last up to an hour. You may be asked to avoid solid food for 24 to 48 hours before the examination and to take a laxative to purge the colon of any stool.
This test uses a CT scan (a type of X-ray procedure) to capture images of the colon which are generated by a computer. It takes less time than standard colonoscopy and requires no sedation, but does not allow the doctor to remove tissues for biopsy and can’t detect polyps smaller than 10 mm. Availability of the procedure varies from province to province.
The best method of screening is colonoscopy as it is most accurate and allows removal of polyps. In addition to being a more sensitive test than an air contrast barium enema in detecting abnormalities in the colon such as polyps, cancer, ulcerative colitis and Crohn's disease, colonoscopy also allows doctors to obtain biopsies and remove polyps through a technique called snare polypectomy. This technique involves a metal loop wire being placed around a polyp and an electrical current being applied to cut the polyp off and seal the base to prevent bleeding.
Most patients with colon cancer have resection surgery where the diseased segment is removed and the bowel on either side of the cancer is reunited. Surgical removal of colon cancer offers a potential for cure. When the growth of the tumour is small, where the cancer has not spread outside the bowel wall, the patient will do well. Larger cancers are typically treated with surgery and afterward the patient may receive chemotherapy (a special drug that kills cancer cells and may be given by mouth or injected through a vein), sometimes in combination with radiation.
Am I going to die if I am diagnosed with colon cancer?
Survival is closely linked with the stage of the disease at the time of surgery. When cancers are still localized to the bowel, the 5-year survival rate is very good -- about 85-95%. Unfortunately, by the time colon cancer causes advanced symptoms, most cancers have spread beyond the bowel and the survival rate is less than 40%. Screening, therefore, is designed to detect and remove polyps early while they are can be completely removed.
How is colon cancer prevented?
It is now well established that effective colon cancer screening using stool tests, sigmoidoscopy and colonoscopy can prevent colon cancer. These screening methods lead to detection and removal of polyps and small cancers that can be easily removed. The use of screening is critical to the prevention of colon cancer.
Is it true that taking aspirin can reduce the risk of colon cancer?
No, a recommendation has not been made by the Canadian Association of Gastroenterology about taking ASA for cancer prevention for the following reasons:
People may think that if they are taking ASA as a preventative measure, they may not go for standard screening which should not be missed if you are over 50, have a family history of colon cancer or polyps, or suffer from inflammatory bowel disease. Colon cancer is over 90% preventable if detected early.
What is the difference between a colonoscopy and sigmoidoscopy?
The difference between colonoscopy and sigmoidoscopy is related to which parts of the colon each can examine. Sigmoidoscopy allows doctors to view only the lower part of the colon, while colonoscopy allows doctors to view both the upper and lower sections. Recent research suggests that colonoscopy is superior to flexible sigmoidoscopy as a colon cancer screening method.
Canadians with family history of colorectal cancer need to be screened earlier, more often.
The Canadian Association of Gastroenterology has released a NEW guideline for colorectal screening.
There is evidence that people with first degree relatives (parents, brothers, sisters or children) with colorectal cancer are at an increased risk.