Colorectal cancer facts

Each week, about 400 Canadians are diagnosed with colorectal cancer, and 167 die of it. This makes it the second most common cause of cancer-related death for Canadians. Most cases are diagnosed in people over the age of 50.

Colorectal cancer is a type of cancer that affects the colon and the rectum, which are part of the bowel. It happens when cells that line the bowels become abnormal and grow out of control, damaging healthy tissues.

Our digestive system processes food by absorbing nutrients and getting rid of solid waste. The bowel is part of our digestive system. Its role is to remove water from our solid waste (this is done in the colon), and to store the waste (this is done in the rectum) until it passes out of the body during a bowel movement.

Usually, colorectal cancer starts as a growth (also called a polyp) in the tissues lining the colon. Not all polyps turn into cancer - only about 1 in 20. A polyp can become cancerous if changes to the polyp's DNA cause the polyp to start growing out of control. Polyps can exist for years without becoming cancerous.

It's very important to catch polyps early, before cancer develops and spreads to other parts of the body.

Risk factors

There are a variety of factors that can increase your risk of colorectal cancer, including:

  • being over 50 years of age
  • having colorectal polyps (now or in the past)
  • having a family member who had or has colorectal cancer
  • having had ovarian, endometrial, or breast cancer
  • having inflammatory bowel disease (ulcerative colitis or Crohn's disease)
  • eating too much red meat
  • not eating enough fruits and vegetables
  • not eating enough fibre
  • not getting enough exercise
  • smoking

If you have any of these risk factors, speak to your doctor about whether you should be screened for colorectal cancer. Even if you do not have any of these risk factors, you should be aware that many people who develop colorectal cancer have no risk factors.


Early colorectal cancer usually doesn't cause symptoms. Later on, symptoms may include:

  • blood in the stool (may appear red or black) or bleeding from the rectum
  • diarrhea, constipation, or other changes in bowel habits
  • feeling tired and weak (which may be a sign of anemia)
  • weight loss with no obvious explanation
  • bowel movements that are consistently narrower than normal
  • feeling like the bowel has not been completely emptied after a bowel movement
  • abdominal cramps, bloating, and fullness

Colorectal cancer is easiest to treat when it is caught early. Because you may not notice any symptoms in the early stages of colorectal cancer, it's important to have regular screening for colorectal cancer, as recommended by your doctor.