What should I know about colorectal cancer?

Colorectal cancer is the 2nd most commonly diagnosed cancer in Canada (excluding non-melanoma skin cancers). It is the 2nd leading cause of death from cancer in men and the 3rd leading cause of death from cancer in women in Canada.

Colorectal cancer responds best to treatment when it is found and treated as early as possible. Knowing about the possible risks, signs and symptoms can help keep you aware of anything you should discuss with your doctor.


What causes colorectal cancer?

There is no single cause of colorectal cancer. Some factors that increase the risk of developing the disease include:

  • Age: particularly for those over 50 years old.
  • Sex: males have higher risks.
  • Polyps: small growths on the inner wall of the colon and rectum.
  • Family history of colorectal cancer, or having familial adenomatous polyposis or Lynch syndrome.
  • Diet high in red or processed meat, and inadquate intake of fruits and vegetables.
  • Obesity.
  • Physical inactivity.
  • Heavy alcohol consumption.
  • Living with inflammatory bowel disease (ulcerative colitis or Crohn's disease).
  • Smoking.
  • Ethnic background: people of Ashkenazi (Eastern European Jewish) descent.

If you have close relatives - parents, siblings or children - who have been diagnosed with colorectal cancer, you are considered to be at a higher risk for the disease, especially if any relatives developed cancer before the age of 45. A condition called familial adenomatous polyposis (FAP) runs in families and also increases the risk. People in families with FAP or with a large number of colorectal cancer cases are often watched closely so that cancer will be diagnosed early if it develops.

What are the signs and symptoms?

Colorectal cancer can develop over a long time without causing any signs or symptoms. When symptoms do start, they can be easily mistaken for more common illnesses. Symptoms get worse if the bowel or rectum becomes obstructed, constricted or ulcerated.

If you have any of the following signs or symptoms, it doesn't necessarily mean you have colorectal cancer. These symptoms could also be caused by other conditions, but it's important to see your doctor to find out. You should talk to your doctor if you see or have:

  • blood in or on the stool
  • a persistent change in normal bowel habits for no apparent reason such as diarrhea, constipation, or both
  • stools that are narrower than usual
  • general stomach discomfort (frequent gas pains, bloating, fullness or cramps)
  • a strong and continuing need to empty your bowels, but with little stool
  • unexplained weight loss
  • anemia (constant tiredness, shortness of breath)
  • vomiting
  • feeling very tired

Are there screening tests for this type of cancer?

“Screening” means checking for colorectal cancer as part of your routine medical care even when you show no symptoms.

The Canadian Cancer Society recommends that men and women age 50 and over have a fecal occult blood test (FOBT) at least every 2 years. FOBT blood testing may identify polyps early before they become cancerous, and can also identify colon cancer prior to it becoming symptomatic.

If you have a positive test, you may need follow up with a colonoscopy or other diagnostic tests.


Additional resources



Prepared by the Canadian Cancer Society. This information appeared originally on the Canadian Health Network Web site.

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