Colorectal cancer screening (colon and rectum)

Colorectal cancer, also called colon and rectal cancer, develops slowly, without any apparent symptoms, and usually from polyps. Polyps are small, benign (non-cancerous) masses of flesh that gradually enlarge on the inner walls of the colon or rectum. Most polyps will remain benign, with no consequences, but some can develop into cancer. It can take years for a polyp to develop into cancer. A person can have a precancerous polyp or even colorectal cancer for years before they have symptoms.

Colorectal cancer screening is an effective way to reduce the risk of developing this disease and its mortality. Screening can detect a cancer precursor polyp or cancer at an early stage. Detecting cancer at an earlier stage also involves less invasive treatments and increases the chances of a cure.

Two tests can be used to detect colorectal cancer, depending on the person’s level of risk:

• The FIT (Fecal Immunochemical Test) detects the presence of blood in the stool that is invisible to the naked eye. In the event of an abnormal result, people can be referred for a colonoscopy.
• A colonoscopy provides a view of the inside of the large intestine and allows polyps or cancer to be detected at an early stage. If polyps are detected, people can receive treatment before signs and symptoms of the disease appear.

A health professional assesses your level of risk, including your personal and family history, and offers you screening or not. Most people at average or high risk could have a free screening test appropriate to their situation (FIT or colonoscopy). People deemed ineligible will be referred to a specialist consultation for care and follow-up.

Most people who are eligible for colorectal cancer screening are at average risk. A FIT is recommended every two years for people at average risk, i.e., people who meet all of the following criteria:

• they are between 50 and 74 years old;
• they do not have any symptoms that may suggest colorectal cancer;
• they do not have a personal history of colorectal cancer, polyps or inflammatory bowel disease;
• they do not have a family history of colorectal cancer, polyps or genetic syndrome;
• they are insured by Quebec’s public health insurance plan.

When the FIT result indicates the presence of blood in the stool, the professional will recommend a colonoscopy to establish the diagnosis. This test visualizes the inside of the large intestine to check for polyps or cancer.

People who meet all of the following criteria are at increased risk:

• they are between 40 and 74 years old;
• they have a family history of colorectal cancer or polyps (without a diagnosis of genetic syndrome);
• they do not have any symptoms that may suggest colorectal cancer;
• they do not have a personal history of colorectal cancer, polyps or inflammatory bowel disease or genetic syndrome;
• they are insured by Quebec’s public health insurance plan.

In the case of an eligible person at increased risk, the health professional determines the appropriate screening method (FIT or colonoscopy) based on each person’s specific family history.

The following people are not eligible for a screening test:

• Those with a personal history of colorectal cancer, polyps or inflammatory bowel disease, or a personal or family history of certain genetic syndromes should consult a health professional and be referred to a specialist for personalized follow-up.
• Those with symptoms who observe a recent and persistent change in their bowel habits (e.g., diarrhea, constipation, black or bright red stools or bleeding after bowel movements) should consult a physician or specialized nurse practitioner immediately for an assessment and treatment.

Cancer in the large intestine (colon or rectum) often leaves traces of occult blood in the stool that are invisible to the naked eye. In order to check whether or not you have blood in your stool, a FIT is recommended. The result of the test cannot determine whether or not you have cancer, but it helps decide if a colonoscopy is necessary.

A FIT consists of taking a sample of your stool at home yourself using the equipment provided in a kit. The sample is then analyzed in a laboratory.

This screening test is recommended for people at average risk and for some people at increased risk.

It is important to learn about the advantages, disadvantages and limitations of screening so that you have all the important information you need to make a decision. Screening is a personal choice. Each person can make an informed decision, based on their values, preferences and priorities, about whether or not to get tested. So it is normal for some people to accept and for others to refuse or to wait before getting tested. A decision support tool can help you decide. If necessary, you can discuss it with a health professional.

Doing a FIT every two years can:

• reduce the risk of developing colorectal cancer. When a colonoscopy is required after a positive FIT, the doctor can see if there are polyps on the inner walls of the large intestine and remove them before they become cancerous;
• reduce the risk of dying from colorectal cancer. Early detection of cancer makes it possible to treat it more effectively, with less aggressive treatment than for advanced cancers, which can improve patients’ quality of life.
  • Out of every 1,000 people who do not participate in screening, three could die from colorectal cancer.
  • Screening 1,000 people for 11 years prevents two deaths from colorectal cancer.

Doing a FIT every two years can, however, have some disadvantages:

• wait times and worry, especially when a colonoscopy is required after a positive FIT;
• possibilities of false positives, that is, the test detects blood in the stool when there is no cancer (e.g., due to hemorrhoids and anal fissures). A colonoscopy will be recommended unnecessarily then. This situation is rare: out of 1,000 people who participate in screening, about 50 get this result;
• possibilities of false negatives, that is, the test did not detect blood in the stool when there is cancer. This situation is very rare: out of 1,000 people who participate in screening, only one gets a false negative result;
• possibilities of overdiagnosis and overtreatment. Overdiagnosis is the discovery of a cancer that would never have been detected without screening, and that would never have had any health effects or life consequences, for example, a cancer that develops very slowly or a harmless cancer. As it is still impossible to differentiate harmless cancers from deadly cancers, they are all treated. Thus, a person who participates in the screening could:
  • have a colonoscopy or receive treatments that would not have been necessary;
  • have side effects from the colonoscopy or these treatments;
  • have to live with a cancer diagnosis;
  • have frequent medical appointments to check that the cancer is not recurring;
  • live with anxiety about the cancer.

Participation in colorectal cancer screening does not guarantee that:

• all colorectal cancers will be detected;
• anyone who has colorectal cancer will survive.

Among people who get a negative (normal) result on the FIT or a normal result on a colonoscopy, some will still develop cancer. This can happen if:

• the cancer could not be detected (e.g., false-negative FIT or colonoscopy that could not visualize a small cancer);
• it is a fast-growing aggressive cancer that developed after the last screening.

It is impossible, when participating in screening, to know in advance exactly who will have benefits or disadvantages.

If you are receiving care from a family doctor or specialized nurse practitioner, you can get a prescription for a FIT. Your health professional will tell you where to get a test kit.

If you do not have a family doctor, you can make an appointment at a local point of service by going to the Clic Santé site or by calling 1-877-644-4545.

Make an appointment

During your appointment, a health professional will do a brief assessment to check if you are eligible for a screening test and will discuss the advantages and disadvantages of participating or not participating in screening with you.

If you are eligible for a FIT and, after discussing it with a health professional, you want to do the test, you will be given a test kit and instruction sheet so that you can take the sample at home. Screening is an option, never an obligation.

All the information you need is provided on an instruction sheet that you will find in the sample kit. The same information is also available on the Instructions for the fecal immunochemical test (FIT) page.

There are three possible results:

• negative (normal);
• positive (abnormal);
• test cannot be analyzed.

The results are available from the health professional who ordered the test or in your medical record at the facility where the test was done. In some cases, the result will be available in your health record after a period of at least one month.

Your result will be negative (normal) if the test does not detect traces of blood in your stool.

You may still have colorectal cancer or develop it. For this reason, it is recommended that you repeat the FIT every two years as long as the result remains negative (normal) and you are still eligible for screening.

Consult your health professional if you notice the appearance of one or more of the symptoms that may suggest colorectal cancer.

Your result will be positive (abnormal) if the test detects traces of blood in your stool. This does not mean that you have colorectal cancer. Other health problems may also be the cause, such as hemorrhoids or anal fissures. This result means that you will be asked to have an additional test, a colonoscopy. This test involves looking at the inside of the intestine with a camera to determine the origin of the bleeding. If you have polyps, they may be removed during the test. If the onset of cancer is detected, you will be treated by a medical team.

In no polyps or cancer are detected during the colonoscopy, it is recommended that the FIT be repeated after 10 years and every two years after this.

Abnormal results are uncommon. Out of 1,000 people who do the screening test, around 50 will have an abnormal result and will have to have a colonoscopy.

A test cannot be analyzed if it has not been done correctly or if too much time has passed between the time you did it and the analysis. You will be asked to do it again and to follow the instructions you received with your test kit. These instructions are also available on the Instructions for the fecal immunochemical test (FIT) page.

A colonoscopy is a test that provides a view of the inside of the large intestine. A health professional may order this test to screen for or diagnose bowel diseases.

It may be recommended for people aged 40 to 74 who are at increased risk of colorectal cancer due to a family history of this type of cancer and who do not have any symptoms suggestive of bowel disease.

The procedure is done on a voluntary basis and you must consent to it based on your values and preferences.

Diagnostic colonoscopy is used in the following situations:

• It may be recommended following a positive (abnormal) result on a FIT.
• It is done periodically for people who have a personal history of colorectal cancer, polyps, inflammatory bowel disease or genetic syndrome.
• It is done as soon as possible to find the cause of intestinal symptoms, such as bleeding from the bowel or severe diarrhea.

The day before your colonoscopy, you will have to follow a special diet and take a laxative to clear all the stool from your intesine. The intestine must be empty for the doctor to examine the inside. If the doctor cannot see the inside of your intestine well, you will need to make another appointment, start the preparation step again and have the test again. So it is very important to follow the recommended diet and take the prescribed laxative. You must also check with the health professional which medications can be taken before the test and which ones must be suspended.

Ask someone ahead of time to drive you. You must not drive a vehicle for up to 24 hours after the test if you are given medication during it. This is how long it takes for the sedative to be completely eliminated from your body. For the same reason, as a precaution, also wait at least 24 hours before making important decisions.

A colonoscopy takes between 15 and 30 minutes. During the test, the doctor inserts a thin, flexible tube, the size of a finger, into your rectum. The tube, called a “colonoscope”, has a tiny camera at the end of it. It allows the doctor to see the inside of the large intestine and transmits the images to a screen.

As the inside of the intestine is easier to see when it is inflated, the doctor pumps gas (air or carbon dioxide) into it. The distension caused by the gas and the movement of the colonoscope can be uncomfortable or painful. The doctor may give you medication (analgesic) to reduce the discomfort or pain. They may also give you a relaxant (sedative) to help you relax during the test.

In addition to examining the inside of the large intestine, the doctor may sometimes also perform other procedures during the test such as removing polyps or doing a biopsy (see below).

A colonoscopy can detect polyps in the intestine. As some polyps can develop into colorectal cancer, the doctors doing the colonoscopy usually prefer to remove them, as a preventive measure.

If they consider it necessary, the doctor may also decide to do a biopsy. This involves removing a small piece of the wall or of a tumour detected inside the colon or rectum.

Removing polyps and biopsies are not painful procedures. The biopsy or polyps collected are analyzed in a laboratory to check whether they are cancerous or not. The results of the analysis will be sent to the doctor who did the colonoscopy and they will follow up with you as appropriate.

Although rare, complications can occur before, during or after the test.

Before the test, headaches or vomiting may be caused by an intolerance to the prescribed laxative.

During the test, several complications may arise, including:

• Some reactions may be caused by the sedative, for example, a drop in blood pressure or respiratory or cardiovascular discomfort.
• Heavy bleeding may occur when the doctor removes polyps or does a biopsy.
• When polyps are removed, the bowel may be perforated (in two cases out of 1,000). Antibiotic therapy or surgery may be required.
• Death can occur in extremely rare cases.

After the test, irritation or inflammation of the wall, sometimes characterized by fever or chills, abdominal pain or a deterioration of your overall condition may occur within 24 to 48 hours after the test.

If complications occur after your colonoscopy, refer to the instructions that the doctor or nurse will give you after your test.