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Colorectal Cancer

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If you or someone you know has been diagnosed with colorectal cancer which is shown by a laboratory test to be MSI-H/dMMR, you may be trying to learn as much as possible about the disease and its treatments. MSI-H is short for MicroSatellite Instability-High. dMMR is short for deficient MisMatch Repair. Read on to find out more.

The information on this website should be discussed with your healthcare professional and does not replace their advice.

An icon representing colorectal cancer

What is colorectal cancer?

Colorectal cancer is cancer in any part of the colon or rectum (large bowel).

Other names for colorectal cancer include colon cancer or rectal cancer. You may also hear people use the term bowel cancer.

The colon and the rectum are one of the last parts of the digestive system. Cancers in these areas can start as a growth on the inner lining of the colon or rectum. These growths are called polyps.

Colorectal cancer most commonly occurs in people older than 50, however it can start at any age.

An icon representing DNA

What is MSI-H/dMMR?

MSI-H/dMMR are biomarkers that can be found in many different types of cancer, including colorectal cancer.

For more information on MSI-H/dMMR cancer click here.

Treatment with KEYTRUDA® (pembrolizumab)

Your doctors will plan your treatment according to your individual circumstances. These include the type of cancer, tumour growth, test results, your expected response to treatment, your age and medical history.

KEYTRUDA is an immunotherapy that may be used to treat certain patients with MSI-H or dMMR colorectal cancer:

  • KEYTRUDA may be used as your first treatment when your cancer has spread or cannot be removed by surgery, and has been shown by a laboratory test to be MSI-H or dMMR. KEYTRUDA is funded for patients who meet specific criteria.
  • KEYTRUDA may be used in adults and children when your cancer has spread or cannot be removed by surgery, and has been shown by a laboratory test to be MSI-H or dMMR, and has progressed after treatment with certain chemotherapy. KEYTRUDA is funded for patients who meet specific criteria.

To determine if KEYTRUDA is a suitable option for you, please consult your doctor.

Glossary

Expand for more information on terms and definitions related to MSI-H/dMMR colorectal cancer.


Terms you may find useful:

Biomarker
A molecule found in our blood, body fluids, or tissues, which can tell us if something normal or abnormal is happening in our body, or if we have a certain condition or disease.

Colon
The main part of the large bowel.

Gastrointestinal (GI) tract
The passage that food travels through from the mouth to the anus.

Oncologist
A doctor who specialises in treating cancer with drug therapies – for example, chemotherapy and immunotherapy.

Polyp
A growth inside the colon or on another body surface.

Prognosis
The expected outcome of your cancer. Your doctor is the best person to ask about your prognosis, but it is not possible for anyone to predict the exact course of cancer.

Rectum
The last part of the large bowel before the anus.

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Questions to ask your doctor

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Patient Resources

References:

National Cancer Institute. NCI Dictionary of Cancer Terms. MSI-H cancer.
Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/msi-h-cancer
Accessed on 20/03/2025

National Cancer Institute. NCI Dictionary of Cancer Terms. Mismatch repair deficiency.
Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/mismatch-repair-deficiency
Accessed on 20/03/2025

Cancer Council Australia. 2025. Understanding Bowel Cancer. A guide for people with cancer, their families and friends.
Available at: https://www.cancer.org.au/assets/pdf/understanding-bowel-cancer-booklet
Accessed on 22/04/2025

National Cancer Institute. NCI Dictionary of Cancer Terms. Biomarker.
Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/biomarker 
Accessed on 20/03/2025

KEYTRUDA Data Sheet

PHARMAC. The Pharmaceutical Schedule.
Available at: https://www.pharmac.govt.nz/pharmaceutical-schedule
Accessed on 26/05/2025

KEYTRUDA Consumer Medicine Information

NZ-KEY-00874v3. TAPS DA 2419KN TAPS NP20132. Last updated June 2025.