About Screening

In the majority of cases, colorectal cancer is preventable and yet each year in Canada, thousands of people are diagnosed with advanced colorectal cancer. If, however, the cancer is detected early through screening, not only may it be highly treatable, but potentially curable. The majority of colorectal cancers begin as benign growths in the lining of the large intestine wall called adenomatous polyps. Over the years (between five and ten years), these polyps grow in size and number, thereby, increasing the risk that the cells in the polyps will become cancerous and invade the wall and move on to other organs. Approximately two thirds of these cancers are found in the large intestine and one third in the rectum. Early removal of these growths will prevent colorectal cancer from developing in the first place. Hence, identification and removal of polyps are key to preventing the development of colorectal cancer.

Clearly, being screened as part of a regular physical exam has the potential to save lives; and patients who are experiencing symptoms related to colorectal cancer should not delay accessing a screening test nor should patients who are at higher risk of developing the cancer.

Did you know?

  1. Most colorectal cancer deaths could be avoided if everyone aged 50 years and older underwent regular screening tests.
  2. It is a common misconception that colorectal cancer is a disease that primarily strikes men. It strikes women almost equally.
  3. More than 90% of the time, colorectal cancer can be effectively treated when diagnosed at its earliest stage through colonoscopy screening.

Sources:

https://basicmedicalkey.com/large-intestine/

https://www.atlantagastro.com/content/colon-cancer-screening

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1411669/pdf/gut00655-0062.pdf

http://www.cancer.ca/en/cancer-information/cancer-type/colorectal/statistics/?region=on


Types of Screening Tests

According to the Canadian Cancer Society, screening or testing, should be performed while the patient is feeling well – so as to find any abnormalities early, before signs and symptoms of disease occur.

The Canadian Task Force on Preventive Health Care (CTFPHC) has issued the following screening recommendations for adults aged > 50 years who are not at high risk for colorectal cancer. They do not apply to those with previous colorectal cancer or polyps, inflammatory bowel disease, signs or symptoms of colorectal cancer, history of colorectal cancer in one or more first degree relatives, or adults with hereditary syndromes predisposing to colorectal cancer (e.g. Lynch Syndrome).

There are several tests used to screen for colorectal cancer and polyps:

  1. Guaiac Fecal Occult Blood Test (gFOBT): A test in which a stool sample may be collected which is returned to the doctor or lab to test for occult (hidden) blood.
  2. Fecal Immunochemical Test (FIT or iFOBT): Uses antibodies to detect human hemoglobin protein in stool. Much like the gFOBT, the test detects the presence of blood in the stools and may be more accurate.
  3. Flexible Sigmoidoscopy: A thin, flexible, lighted with a small video camera located at its end is inserted through the anus in order to view the inside of the lower colon and rectum (usually about the lower 2 feet) for polyps and cancers.
  4. Colonoscopy: A thin, flexible, lighted with a small video camera located at its end is inserted through the anus in order to view the inside of the lower colon and rectum (usually about the lower 2 feet) for polyps and cancers.
  5. CT Colonography (Virtual Colonoscopy): A less invasive test using special x-ray equipment to produce pictures of the colon and rectum.
  6. Stool DNA Test or Fecal DNA Testing: Much like the FOBT and FIT, the stool DNA test screens a stool sample but instead of looking for blood, it looks for DNA that may signal the presence of cancer or polyp in the colon.

Screening Guidelines in Canada

While various organizations, including CCC, work to increase the number of individuals getting screened appropriately and to promote high quality cancer screening services across the country, in Canada each province/territory is responsible for establishing its own screening guidelines for colorectal cancer. These guidelines pertain to individuals in the following three categories: asymptomatic, average risk and high risk.

A list of colorectal cancer screening resources for each province and territory can be found here.

In addition, The Canadian Task Force on Preventive Health Care (CTFPHC), established by the Public Health Agency of Canada, published national clinical practice guideline recommendations for colorectal cancer screening in 2016. They recommend individuals at average risk, aged 50-74, screen for colorectal cancer with an FOBT [either fecal test guaiac (FTg) or FIT] every 2 years or flexible sigmoidoscopy every 10 years.

Additionally, the Canadian Task Force on Preventive Health Care does not recommend the following:

  • Screening individuals aged 75 and over for colorectal cancer
  • Using colonoscopy as a screening test for colorectal cancer