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March is colorectal cancer awareness month

Diagnosing Colorectal Cancer

Receiving a cancer diagnosis can be overwhelming. As you begin your cancer journey, allow yourself to be present with your full range of emotions, communicating with those who are there to support you.

You may alternate between feeling intense emotions such as panic, outrage, anger, guilt, or in some cases, despair. You can manage your emotions by gathering accurate information, resources and support. But remember, you are the same person as you were the day before you were diagnosed.

Newly Diagnosed Patient Video


Before you begin any treatment, the first step will be to learn more about your colorectal cancer so that you understand the treatments available to you as well as their potential side effects. . To help you navigate these important discussions with your care team, download our list of Questions to ask your health care team when you have been diagnosed with cancer.

Shared decision making

Shared decision making is a key component of patient-centered health care. When you participate in shared decision-making, you are actively working with your doctor to make decisions and select tests, treatments and care plans that are best suited to you.

Take time to learn about your options

When you first hear the diagnosis of colorectal cancer, a natural reaction may be to seek immediate treatment. But colorectal cancer usually grows slowly, and in many cases, immediate treatment is not needed. It is more important to take the time to learn about your options, gain perspective and seek additional information or opinions if necessary before deciding on a course of treatment.

More colorectal cancer treatment options than ever before

Today there are more treatment options available, and your preferences and values are very important in selecting the right ones for you. Your doctor will inform you about the pros and cons of each option, and you will work with them to agree on an approach including the optimal sequencing of therapies. Furthermore, depending on your diagnosis, you may be eligible to participate in a clinical trial – a possible treatment option that can offer access to promising new therapies and therapeutic approaches at any cancer stage.

If at any time you have questions or are confused by a treatment option, be sure to ask! Being as informed as possible can be helpful during this process.


Cancer affects both your physical and emotional health, and it is important to address the range of feelings you may be experiencing. Visit our Patient & Family Support page for more information, including how to participate in our support groups.

Personalized healthcare in cancer care

Cancer care has been at the forefront of personalizing healthcare. Personalized medicine can be described as receiving: “the right medicine for the right patient at the right time”.

Personalized healthcare (PHC) is commonly considered as a shift away from the “one-size-fits-all” approach, towards one in which healthcare is based on the individual’s biological characteristics within a specific sociocultural and environmental context. It uses information about a person to prevent, diagnose and treat disease.

Benefits of personalized healthcare

Through PHC, health care providers can offer and plan specific care for you, based on your genetic makeup and cancer cell genes. Essentially, it looks at how a specific gene mutation might affect your risk of getting a certain cancer or, if you already have cancer, how your cancer genes might affect treatment.

  • Diagnosis and targeted therapy: Greater access to biomarker testing, which includes genomic profiling allows oncologists to profile your cancer to determine the majority of genetic mutations present. In most cases, this genetic information can be used to match patients to more accurate diagnosis and targeted therapy. In other cases, it can help people make decisions about healthy habits, earlier screening tests, and other steps towards prevention if they are at risk for a particular cancer.

  • Informed decision making: Implementing PHC will allow more informed decisions to be made in collaboration with you and your care team. This includes not only decisions on the type of treatment, but also on more holistic healthcare strategies such as where and how treatment, monitoring and support can be given to you. This helps to improve your experience and optimize treatment benefits.

  • Improving future of healthcare treatment and patient outcomes: We believe that with patient consent, health professionals can collect and share data in the aggregate with healthcare organizations to improve knowledge, accelerate research into new treatment approaches and enable more informed decisions with the goal of improving patient outcomes. In sharing data, patients can become the drivers of change for their own disease and for patients like them, helping to advance PHC for all.

Limitations of PHC

For most cancer patients, access to PHC is inconsistent and challenging. Some patients may not be familiar with what PHC is and how it can benefit them and the cancer community.

Colorectal Cancer Canada can help inform you about PHC so that together we can advocate for broader access to PHC in Canada and empower patients to more effectively participate in their healthcare decisions. PHC can be integrated more broadly and cost-effectively into the healthcare system and together we can make a difference!


ESMO Patients Guide Series ESMO Personalized Medicine

National Cancer Institute

Canadian Cancer Society

Colorectal Cancer Screening and Diagnostic Tests

Detecting colorectal cancer early by screening increases the chances of detecting precancerous growths and removing them before they spread to other parts of the body.

Who qualifies for colorectal cancer screening?

Screening is done on men and women beginning at 50 years of age even though they may not have any signs or symptoms of the disease. If you have a direct family member who had colorectal cancer at 50 years of age or younger, you may be considered to be at an elevated risk and screening will begin 10 years earlier than your family member who was diagnosed with colorectal cancer.

How is colorectal cancer diagnosed?

Colorectal cancer may be diagnosed through various tests, including:

  • a fecal immunochemical test (FIT)/immunochemical fecal occult blood test (IFOBT)/fecal occult blood tests (FOBT)

    or in the case of a positive FIT/FOBT,

  • a colonoscopy.

If a screening test has come back with abnormal results, or if you are experiencing symptoms, additional testing is required to check for the presence of colorectal cancer. Once all the outcomes have been put together, your doctor will review these results with you.

The following tests are usually used to rule out or diagnose colorectal cancer.

  1. Digital rectum exam

    This is an examination of your back passage (rectum), which involves your doctor feeling inside your rectum using their finger.

  2. CT colonography

    In computer tomography (CT), many X-ray images of the colon and rectum are taken and combined by a computer. This produces a three-dimensional, detailed image that allows the doctors to examine the tissues for cancer.

  3. Flexible sigmoidoscopy

    This test looks inside the lower part of your large bowel using a thin flexible tube called a colonoscope that has a small light and camera at one end. The tube is inserted into your back passage and gently moved up into the lower part of your bowel.

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  1. Blood tests

    There are several blood tests that can be performed as a first step to diagnosing colorectal cancer.

    • A full blood count (FBC) measures the number of red cells, white cells and platelets in your blood.

    • Liver function tests (LFTs) check how well your liver is working.

    • Urea and electrolytes check well your kidneys are working.

    • Tumor markers which are substances (usually proteins) that might be raised if there is a cancer. They can be found in the blood, urine or body tissues.

  2. Colonoscopy

    An endoscopist uses a flexible tube (colonoscope) that has a small light and camera at one end to look at the whole of the inside of your large bowel.

  3. Biopsy

    A biopsy is done by a pathologist on a sample of cells removed from tissue from your bowel. This test helps to discover whether cancer is present.

After someone is diagnosed with colorectal cancer, the next step generally is to classify the cancer based on how much the disease has spread at the time of diagnosis. This allows your doctor to make the best recommendation for treatment options tailored specifically to your Stage of cancer.

Radiology/Nuclear Exams

Many of the same tests used to diagnose cancer are used to determine the Stage. Other tests include:

  1. Computed Tomography (CT) scan

    A CT scan is a test that uses x-rays and a computer to create detailed pictures of the cancer. It takes pictures from different angles, and a computer puts them together to make a 3-dimensional (3D) image.

  2. Positron Emission Tomography (PET)

    A PET scan is an imaging test that uses a radioactive drug (tracer) to show the activity of the tissues and organs of the body. The tracer may be injected, swallowed or inhaled, depending on which organ or tissue is being studied. The tracer collects in areas of the body that have higher levels of chemical activity, which often correspond to areas of disease. On a PET scan, diseased areas such as cancer show up as bright spots.

    Sometimes CT and PET are combined:

    A PET CT scan combines a CT scan and a PET scan into one to give more detailed information about your cancer. These scans may also be combined with an MRI scan.

  3. MRI scan

    MRI (magnetic resonance imaging) uses magnetism and radio waves to create cross sectional pictures of the body. It produces pictures from angles all around the body and highlights soft tissues very clearly.

  4. Ultrasound scan of the rectum

    Most commonly done for rectal cancer, this scan uses ultrasonic sound waves to look at the inside of your rectum. This could give information to your doctor such as how far it has grown through the rectal wall, and whether it has spread further.

  5. Ultrasound scan of abdomen

    Similarly, this scan uses ultrasonic sound waves to look at the abdomen and check if the cancer has spread there.

Resources to help you understand your pathology report

Tumour Staging

Tumour staging is the process of finding out how much the cancer has spread is in your body and where it is located. The stage of your cancer is the major determinant of appropriate treatment and prognosis. It helps your doctor to decide which treatment will be most appropriate for you.

For a detailed look at colorectal cancer staging, visit's Colorectal Cancer: Stages

TNM staging system

The TNM staging system is the most widely used cancer staging system. In a colorectal cancer diagnosis, you are likely to see the cancer described by this staging system in the pathology report.

T category describes the primary Tumor site N category describes the involvement of cancer cells in the lymph Nodes by the colon M category describes the presence of cancer beyond the colon and its adjacent tissues such as to organs like the lungs or liver (Metastases).

Tis. The cancer is confined to the innermost layer of the colon or rectum

N0. There is no spread to lymph nodes

T1. The cancer has grown through the first few layers of the colon or rectum

N1. Cancer is found in 1-3 lymph nodes

T2. The cancer has grown into the thick muscular layer of the colon or rectum

N2. Cancer is found in four or more lymph nodes

T3. The cancer has grown through the entire colon or rectum wall

M0. There is no spread of cancer to distant organ(s).

T4. The cancer has grown through the entire colon or rectum wall and into nearby tissue or organs

M1. Cancer is found in distant organ(s).

Number staging system

This system uses the TNM system to divide cancers into stages.

Stage 1 (I): The cancer is relatively small and contained within the organ it started in (T1-N0-M0 or T2-N0-M0)

Stage 2 (II): Can be divided into stages 2A (T3-N0-M0), 2B (T4-N0-M0). The tumor is larger than in stage 1, but the cancer has not started to spread into the surrounding tissues. Sometimes stage 2 means that cancer cells have spread into lymph nodes close to the tumor.

Stage 3 (III): Stage 3 can be divided into stages 3A (T1/2-N1-M0), 3B (T3/4-N1-M0), and 3C (any T-N1-M0), depending on where the tumor has grown and how many lymph nodes have cancer. Generally, the cancer is larger. It may have started to spread into surrounding tissues and there are cancer cells in the lymph nodes in the area

Stage 4 (IV): The cancer has spread from where it started to another body organ (metastatic cancer). The cancer may be in only 1 organ or in distant lymph nodes (stage 4A). It may be in more than 1 organ (stage 4B). The cancer may be in the peritoneum (stage 4C) (any T-N-any N-M1),

Duke’s Staging system

This staging system is a classification system specific to colorectal cancer. Today, it has been largely replaced by the TNM staging system.

Dukes Stage A bowel cancer

The cancer is only in the inner lining of the bowel

Dukes Stage B bowel cancer

The cancer has invaded the muscle

  • Stage B1: Tumor limited to the submucosa, no lymph node invasion.

  • Stage B2: Tumors confined to the muscle layer, no lymph node invasion.

Dukes Stage C bowel cancer

The cancer has invaded the nearby lymph nodes

  • Stage C1: The tumor did not exceed the bowel wall, lymph node metastasis.

  • Stage C2: Tumor exceeded the intestinal wall and lymph node metastasis.

Dukes Stage D bowel cancer

The cancer has metastasized


Biomarkers (short for biological markers) are molecules found in body tissues and fluid, including tumour tissue and blood. They are sometimes referred to as tumour markers or molecular markers. When certain biomarkers are present, it tells your doctors valuable information about your colorectal cancer.

Treating colorectal cancer today is different than it was a few decades ago. In the past if you had colorectal cancer, you might have received the standard therapy used for all people with colorectal cancer. We now understand that two people with colorectal cancer may have very different kinds of tumours at the cellular level.

Biomarkers for personalized cancer care

The use of biomarkers has helped to create a more personalized approach to cancer care that will be the most beneficial to you with the least amount of side effects.

There are different categories of biomarkers that give different information about cancer. Some can tell your doctors about how a tumour might behave in the future in response to treatment, while others can indicate whether cancer cells are still present in a patient after treatment.

When is biomarker testing done?

Biomarker testing is sometimes called molecular testing, tumour testing, or genomic testing. The best time to do testing is soon after a colorectal cancer diagnosis and before a treatment plan is chosen. Even if you were not able to do biomarker testing before you started treatment, it may still be worthwhile to do since it could affect how your current treatment plan progresses.

After a colorectal cancer diagnosis, surgery may be performed to do a biopsy of the tumour. A biopsy removes a small piece of the tumour to examine its characteristics. Then, the tumour is tested in a laboratory for the known biomarkers that impact colorectal cancer patients.

Get Personal Program

Learn more about colorectal cancer biomarkers below:


KRAS (Kirsten rat sarcoma) is a gene that is involved in promoting the growth and division of colorectal cancer cells. It is part of a pathway in the cell that relies on a specific receptor found on the surface of cells called the epidermal growth factor receptor (EGFR). When KRAS is abnormal or mutated as in 35-45% of colorectal cancer patients, the class of targeted therapy drugs known as EGFR inhibitors may not be a useful treatment.

KRAS wild-type

The natural, unchanged form of the KRAS gene is referred to as KRAS wild-type. Patients whose biomarker test shows that the tumour is KRAS wild-type may respond well to treatment plans that include EGFR inhibitors.


NRAS is a gene that is involved primarily in regulating cell division and like KRAS, is also involved in the EGFR-mediated pathway in the cell. NRAS mutations occur in less than 5% of colorectal cancer tumours. Similar to KRAS, if a patient’s biomarker test shows an NRAS mutation, EGFR inhibitors may not be a useful treatment.

NRAS-wild type

The natural, unchanged form of the NRAS gene is referred to as NRAS wild-type. Patients whose biomarker test shows that the tumour is NRAS wild-type may respond well to treatment plans that include EGFR inhibitors.


BRAF V600E refers to a specific mutation in the BRAF gene, which is involved in cell division. With the V600E mutation, the BRAF gene drives the proliferation of cancer cells, and has been linked to poor disease outcomes in patients. Patients with BRAF V600E mutations do not respond well to EGFR inhibitors.

The BRAF-inhibitor Encorafenib (Braftovi®) in combination with the EGFR-inhibitor cetuximab (Erbitux®) has show positive results in the treatment of BRAF V600E metastatic colorectal cancer. The combination therapy has recently been approved in the United States for this subset of colorectal cancer patients.

Some patients with BRAF V600E-mutated colorectal cancer also have microsatellite instability, which means that this subset of patients may be responsive to immunotherapy drugs such as nivolumab (Opdivo®) and pembrolizumab (Keytruda®).

BRAF non-V600E

In metastatic colorectal cancer, mutations of the BRAF gene most commonly are V600E. Non-V600E BRAF mutations occur in about 1% of metastatic colorectal cancer patients. Similar to patients with mutated KRAS or NRAS genes, patients with a BRAF mutation may not respond well to EGFR inhibitors, nor to standard chemotherapy.


The PIK3CA gene is involved in cell growth and division. Mutations in this gene have been associated with minimal benefits from EGFR inhibitors.


Microsatellite Instability – high (MSI-H)/mismatch repair deficient (dMMR) is a status that is given to patients when the genes that fix DNA errors as it is dividing, the mismatch repair genes, are unable to do their job. When these genes are not functioning properly, the DNA can become unstable because of the errors and can lead to various kinds of cancer including colorectal. If this instability is present in a tumour, it is classified as MSI-H.

About 25% of MSI-H or dMMR tumours are associated with the hereditary syndrome, Lynch syndrome. About 5% of patients with metastatic colorectal cancer will have MSI/dMMR tumours. This subset of patients is more likely to benefit from immunotherapy treatment, such as nivolumab (Opdivo®) or pembrolizumab (Keytruda®).


Carcinoembryonic antigen (CEA) is one of the most widely used biomarkers in the world. It is a protein that is found on the surface of colorectal cancer cells. CEA tests may be used to find out if cancer treatment is working, or to find out if cancer has come back after treatment.

After treatment, a return to a normal CEA level that was previously high usually means that the cancer has responded to treatment. A CEA level that rises after treatment has ended usually means that the cancer has come back.

CEA blood level may also increase in non-cancerous conditions such as inflammatory conditions of the colon or rectum, such as ulcerative colitis.

Sidedness/location in the colon

Where colorectal cancer is located in the colon can impact a patient’s disease outcomes. Tumours that are found in the right side of the colon compared to the left side of the colon show different characteristics at the molecular level. As a result, left-sided and right-sided tumours tend to respond differently to treatment.

Left-sided tumours

Left-sided tumours generally have better disease outcomes, responding to 5-FU-based chemotherapy regimes as well as targeted therapies such as EGFR inhibitors.

Right-sided tumours

Right-sided tumours tend to respond poorly to conventional chemotherapies, but are showing promising response to immunotherapy such as pembrolizumab (Keytruda®).


HER2 is a gene that is involved in cell division. Increased levels of HER2 expression is found in about 2-6% of patients with stage 3 or 4 colorectal cancer. The presence of a HER2 mutation has been associated with poor response rates to EGFR inhibitors.

Trastuzumab Detuxtecan (T-Dxd) is a targeted therapy drug approved for the treatment of HER2-positive metastatic breast cancer. It has been shown to also be effective in HER2-positive metastatic colorectal cancer. The phase II DESTINY-CRC01 study found that the treatment provided an overall survival benefit for this subset of colorectal cancer patients compared to the standard of care.

TRK fusions

When the NTRK gene joins or “fuses” with an unrelated gene, it produces signaling in the cell that can cause cancerous tumours to grow. While TRK fusions are very rare, if they are detected they present a possible treatment option with drugs that specifically target NTRK-fusion positive metastatic colorectal cancer, such as entrectinib (Rozlytrek®) and larotrectinib (Vitrakvi®) .


Circulating tumour DNA (ctDNA) are small pieces of DNA present in the bloodstream which originate from tumour cells. Most DNA is contained within the cell’s nucleus. As a tumour grows, however, cells will die and get broken down. Their contents, including DNA, are then released into the bloodstream. The quantity of ctDNA can vary among individuals and will depend on the tumour type, its location, and the cancer stage. Testing for ctDNA is sometimes referred to as liquid biopsy.

Detection of ctDNA can be helpful in the following ways:

  • Detecting and diagnosing a tumour

  • Guiding a more personalized approach to cancer treatment

  • Monitoring treatment, where a decrease in the quantity of ctDNA suggests that the tumour is shrinking and treatment is working

  • Monitoring cancer recurrence, where a lack of ctDNA in the blood suggests that the cancer has not returned.

In Canada, some tests detecting ctDNA are already being used but they remain reserved for people with a known cancer diagnosis. For example, one test screens for ctDNA from people with advanced cancer to look for for specific mutations that could be selectively targeted by available drugs. Liquid biopsy is especially useful when a tissue biopsy is not possible. Current research aims to refine ctDNA screening tests to expand their use to early cancer detection.

The Access to Cancer Testing and Treatment program, also known as Project ACTT, is a federally-funded program in partnership with Canexia Health to provide liquid biopsy testing to 2,000 patients across Canada who have advanced or metastatic breast, lung, and colorectal cancer. Formerly known as Canadian Early Access Program, it was initially launched in 2019 to provide oncologists and patients with access to a blood-based ctDNA mutation panel known as Follow It.

For more information about Project ACTT’s liquid biopsy testing in Canada, see Canexia Health’s informational pamphlets below.

Last updated: July 2021


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