Colon Cancer

Colon Cancer

What is Colon Cancer?

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

  1. Over time, as the polyps grow some of them turn malignant or cancerous
  2. These cancers can grow into the wall of the colon and spread to other parts of the body
  3. Depending on the amount of spread, colon cancer is assigned a number from 0 to 4 (called staging).

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.

Can I prevent colon cancer?

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.

Living Positively

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.

Lifestyle changes to help prevent colon cancer

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:

  • Colorectal cancer is the 2nd most commonly diagnosed cancer in Canada, after lung cancer. It accounts for a projected 26,800 new cases in 2017 (13% of all cancers). (Canadian Cancer Society's Advisory Committee on Cancer Statistics 2017; Public Health Agency of Canada 2017)
  • Colorectal cancer kills more Canadians than any other digestive cancer. It has the 2nd highest death rate of all cancers in Canada. (Canadian Cancer Society's Advisory Committee on Cancer Statistics 2017; Public Health Agency of Canada 2017)
  • 1 in 13 men and 1 in 16 women are expected to develop colorectal cancer during their lifetimes; 1 in 29 men and 1 in 34 women will die of it. (Canadian Cancer Society's Advisory Committee on Cancer Statistics 2017; Public Health Agency of Canada 2017).
  • About 1 in 2 cases is diagnosed in a late stage. The most common stage at diagnosis is stage III (29% of cases). About 20% of cases are at stage IV at diagnosis. (Canadian Cancer Statistics Advisory Committee 2018)
  • Five-year survival for colon cancer is estimated to be 92% for cancers diagnosed at stage I compared with only 11% for stage IV. Five-year survival for rectal cancer is estimated to be 87% for stage I and 12% for stage IV. (Canadian Cancer Statistics Advisory Committee 2018)
  • The economic burden of colorectal cancer in Canada is substantial. Acute inpatient care costs for colorectal cancer totaled nearly $215 million in 2004-2005. (Canadian Digestive Health Foundation 2009).


Canadian Cancer Society’s Advisory Committee on Cancer Statistics. Canadian Cancer Statistics 2017. Toronto, ON: Canadian Cancer Society; 2017. [accessed 3 September 2018]

Canadian Cancer Statistics Advisory Committee. Canadian Cancer Statistics 2018. Toronto, ON: Canadian Cancer Society; 2018. [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. [accessed 3 September 2018]

Signs and Symptoms of colon cancer

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:

  • Blood in the stools: The blood may be bright red if the tumour is near the end of the colon or anus, but usually it is hidden inside the stools
  • Loss of weight without trying and/or loss of appetite
  • Nausea and vomiting: A large tumour may block the colon and prevent the digestive contents from moving forward causing a backup of food which can lead to nausea and vomiting
  • Fatigue due to anemia: Tumours tend to bleed, which means you lose iron. This can lead to iron-deficiency anemia and accompanying feelings of extreme fatigue. A blood test can determine whether you have anemia.
  • Diarrhea for more than a couple of weeks
  • Narrow stools: This may signal an obstacle that is squeezing the waste
  • Sense of fullness in the rectal area: A tumour toward the end of the colon or in the rectum may produce a sensation of “having to go.” You may also have a feeling that your bowels aren’t emptying completely
  • Gas and bloating: This may indicate that a tumour is obstructing the passage of stool which traps air and leads to gas and a bloated feeling.
  • Altered bowel habits, such as: o Going to the bathroom more or less often than usual o Constipation: This may happen if the tumour is blocking part of the bowel
  • Abdominal pain or discomfort (e.g., cramps)

Risk factors for colon cancer

A risk factor is something that makes you more likely than average to develop a condition. Ask yourself the following:

  • Are you 50 years of age or older?
  • Do you have a family history of colon cancer?
  • Do you have Crohn’s disease or ulcerative colitis?
  • Have you had a prior diagnosis of polyps or early-stage colon cancer?
  • Do you have a diagnosis or family history of hereditary syndromes linked to colon cancer?
  • Do you eat a diet high in calories, fat and processed meats, and low in fibre, vegetable and fruits? Research suggests such a diet may raise the odds of developing colon cancer.
  • Are you inactive? This can increase your chances of getting colon cancer because inactivity causes waste (stools) to stay in your colon longer.
  • Are you obese?
  • Do you smoke?
  • Do you drink a lot of alcohol?

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.

Tests and Treatment

While each province/territory has its own screening recommendations, common screening tests include: Stool Tests

Fecal occult blood test (FOBT):

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.

Fecal immunochemical test (FIT):

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.

Virtual colonoscopy:

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.

Treating colon cancer

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:

  1. The evidence of ASA reducing the risk of colon cancer is largely circumstantial. While interesting, there have been no actual trials designed to look at colon cancer reduction with ASA
  2. There are hazards associated with taking ASA, including bleeding in the intestinal tract, which are typically at par with the reduction of risk of cancer.

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.

Protecting Yourself from Colon Cancer
Healthy Gut Summit 2016 presentation by Dr. David Armstrong on protecting yourself from Colon Cancer.

NEW Guideline for Colorectal Screening

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.

Proper Bowel Prep Can Save Your Life
Too many people skip potentially life-saving procedures because of misunderstandings and misconceptions about the bowel prep. However, most people who have had colonoscopies, will tell you it isn't nearly as bad as you think and that the benefits far outweigh the risks. Robbie, Anne and Laurie, who range in age from 11 to 80 years, openly share their experiences with you in this video.