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Screening for colorectal cancer
Screening means checking or testing for a disease in a group of people who don’t show any symptoms of the disease. Screening tests help find colorectal cancer before any symptoms develop. When colorectal cancer is found and treated early, the chances of successful treatment are better.
Who should have a stool test
If you are 50 to 74 years old and not at high risk for colorectal cancer, have a stool test every 2 years. If you are 75 or older, talk to your doctor about whether a stool test is right for you.
There is convincing evidence that stool tests with the right follow-ups can lower the number of deaths from colorectal cancer.
A stool test checks for hidden (occult) blood in the stool. Cancerous tumours and other growths in the lining of the colon or rectum (such as polyps) have blood vessels on their surface that can release a small amount of blood into the stool. Stool tests help identify adenomas (adenomatous polyps) early, before they become cancerous.
There are 2 types of stool tests used to screen for colorectal cancer in Canada.
- gFOBT (guaiac-based fecal occult blood test) is the original type of stool test. It uses a chemical reaction on a paper card to find blood in the stool from adenomatous polyps or tumours.
- FIT (fecal immunochemical test) uses specific antibodiesantibodiesA type of protein made by the immune system that disarms or destroys a specific foreign substance (antigen) when it appears in the body. for human blood to find blood in the stool. FIT is being used by most screening programs in Canada.
Find out more about stool tests.
Follow-up after screening
A positive stool test result means that blood has been found in the stool. People who have a positive result will need to have follow-up tests. They include:
- colonoscopy – a test that lets the doctor look at the lining of the whole colon using a long, thin, lighted tube
- flexible sigmoidoscopy – a test that lets the doctor look at the lining of the rectum and lower part of the colon using a thin, flexible tube
- double-contrast barium enema – an x-ray of the colon and rectum
A negative stool test result means that blood has not been found in the stool. If you have a negative stool test result, you should have another stool test in 2 years.
See your doctor if you have blood in the stool, bleeding from the rectum or other signs and symptoms of colorectal cancer in between stool tests.
Screening programs in Canada
Most provinces have organized colorectal cancer screening programs with specific guidelines. Although the guidelines may be different in each province and territory, all guidelines include regular stool tests to help find colorectal cancer early.
Make sure to read the instructions included with your stool test. Depending on the type of test and your province, there might be medicine or food restrictions. And each program will have instructions on how to provide a sample and how to return the test.
Ask your doctor about how the program works where you live.
You can also call the Canadian Cancer Society’s Cancer Information Service toll-free at 1-888-939-3333 for information about colorectal cancer and screening programs.
Know what puts you at high risk
Some people have a higher risk of colorectal cancer. People at higher risk may need to be tested more often and at an earlier age than people with average risk. You may be at higher risk if you have:
- a parent, sibling or child with colorectal cancer
- a personal history of colorectal cancer
- a personal history of non-cancerous (benign) polyps in the colon or rectum
- inflammatory bowel disease (ulcerative colitis or Crohn’s disease)
- inherited conditions, such as familial adenomatous polyposis (FAP) or Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC)
- signs or symptoms of colorectal cancer
Talk to your doctor about your risk. If you are at higher risk, you may need a personal plan for testing. This may include:
- stool test (gFOBT or FIT)
- genetic risk assessment, counselling and testing, if available
- flexible sigmoidoscopy
- double-contrast barium enema
Questions to ask your healthcare team
To make the decisions that are right for you, ask your healthcare team questions about screening.