Colorectal cancer, commonly known as colon cancer, generally develops very slowly. A person can have the cancer for years without showing any symptoms.
Screening aims to detect and treat colorectal cancer before the onset of signs and symptoms. Usually, at the time of screening, the cancer is at an early stage and the chances of curing it are higher.
Who is eligible
Screening is mainly aimed at people at average risk. Indeed, it is recommended that people who are 50 to 74 years old and at average risk (no symptoms or other risk factors) get screened for colorectal cancer every 2 years, since the risk of developing colorectal cancer increases after the age of 50.
Screening can begin before the age of 50 for people who have a higher risk of developing colorectal cancer.
People at average risk
In Québec, screening for colorectal cancer in individuals at average risk, without symptoms and other risk factors, is recommanded every 2 years. Screening is done using the immunochemical fecal occult blood test (iFOBT). This test does not show whether you have colorectal cancer or not, but it detects the presence of blood in the stool, which can be a sign of cancer.
When results of an iFOBT indicate the presence of blood in the stool, the health professional recommends another exam called a colonoscopy. This procedure permits the examination of the large intestine to check whether or not there is a cancer.
People at high risk
In the case of individuals at high risk, the health professional determines the screening method according to each person’s particular situation.
If this is your case, discuss with your health professional about recommendations that apply to you.
Benefits and limitations of screening with an iFOBT
You can decide whether or not to do a colorectal screening test. It is a personal choice that belongs to you. If you have questions or concerns on the matter, discuss them with your health professional.
Screening reduces the risk of dying of colorectal cancer. For every 1,000 individuals screened, 5 deaths are prevented.
Colorectal cancer usually develops very slowly. Getting an iFOBT every 2 years increases the chances that the cancer is discovered and treated at an early stage. The necessary treatments could also be less aggressive.
In addition, when a colonoscopy is necessary, the doctor can see if there are polyps on the inner lining of the large intestine. Polyps are small masses of flesh that can transform into colorectal cancer. The doctor can thus remove them before they become cancerous.
Despite all the benefits, screening with an iFOBT is not perfect.
In some cases, the test can detect blood in the stool without there being cancer or polyps
Such cases are rare. Of 1,000 individuals that take the test, about 15 people receive this result. These few people must subsequently have a colonoscopy that is not needed and may have polyps removed unnecessarily.
In addition, colonoscopies may result in certain complications. To learn more, see the Colonoscopy page.
On the contrary, people who have colorectal cancer may receive a negative test result
This happens in about 20% of people with colorectal cancer. Their cancer goes undetected. Indeed, no screening test, colonoscopy included, guarantees that a cancer will be detected. That’s why it is recommended that you do the iFOBT every 2 years in order to increase the chances of detecting cancer.
Screening allows detection of the cancer when it is in its early stages and increases the chances of healing. However, a number of people die each year from colorectal cancer even if they had a screening.
A few statistics
Of 1,000 people that take an iFOBT, 36 will receive a positive test result and will then have a colonoscopy. Of these 36 people: