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MSI-H/dMMR Cancer

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If you or someone you know has been diagnosed with cancer which is shown by a laboratory test to be MSI-H or dMMR, you may be trying to learn as much as possible about your cancer 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.

What is MSI-H/dMMR cancer?

MSI-H/dMMR are biomarkers that can be found in many different types of cancer. However, they are most often found in cancers of the colon, rectum, endometrium, and stomach.

Biomarkers can be detected in blood, other body fluids or tissues.

An icon representing DNA

What causes MSI-H/dMMR?

Normal cells have a system that detects and repairs mistakes that happen when your DNA is copied. It’s called the DNA mismatch repair (MMR) system.

Sometimes the system stops working properly. MSI-H/dMMR can occur when a cell is unable to repair mistakes. When this happens, errors in the DNA mount up and may cause cancer.

MSI-H/dMMR can be hereditary (passed down through families), for example with Lynch syndrome. It can also be random with no family connection.

An icon depicting a laboratory microscope.

Who should be tested for MSI-H/dMMR?

Everyone’s cancer is different. To help develop a treatment plan that’s right for you, your doctor may order laboratory tests. These tests can assess your cancer for different biomarkers, including MSI-H or dMMR.

Some biomarkers are used to help predict if you are likely to respond to certain treatments. The Ministry of Health recommends that all newly diagnosed patients with colorectal cancer in New Zealand are tested for dMMR.

Treatment with KEYTRUDA® (pembrolizumab)

Your doctor will plan your treatment according to your individual circumstances. These include your type and stage of cancer, and result of your biomarker test. They will also consider any previous treatments you may have received and your general health.

KEYTRUDA is an immunotherapy that may be used:

  • As the first treatment in adults to treat colorectal cancer that has spread or cannot be removed by surgery (advanced cancer) and has been shown by a laboratory test to be MSI-H or dMMR.
  • In adults and children to treat advanced colorectal cancer which has been shown by a laboratory test to be MSI-H or dMMR, and who have received other treatments which have not worked or are no longer working.
  • In adults and children to treat advanced cancer of any part of the body which has been shown by a laboratory test to be MSI-H or dMMR, and who have received other treatment which has not worked or is no longer working, and there are no other satisfactory treatment options.

It is not known if KEYTRUDA is safe and effective in children with MSI-H cancers of the brain or spinal cord (central nervous system cancers).

Talk to your doctor to see if KEYTRUDA may be right for you.

KEYTRUDA is not funded in New Zealand for the treatment of patients with MSI-H/dMMR cancer.

Glossary

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

Biomarker test
A laboratory test used to search for molecules in our body, like genes, proteins, and other substances (biomarkers), which can give us important information about cancer.

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

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.

Tumour
A new or abnormal growth of tissue. Tumours can be benign (not cancerous) or malignant (cancerous).

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Questions to ask your doctor

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Patient Resources

References:

National Cancer Institute. Dictionary of Cancer Terms. MSI-H cancer.
Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/msi-h-cancer
Accessed on 17/12/2019

National Cancer Institute. Dictionary of Cancer Terms. Mismatch repair deficiency.
Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/mismatch-repair-deficiency
Accessed on 17/12/2019

National Cancer Institute. Dictionary of Cancer Terms. Biomarker.
Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/biomarker
Accessed on 17/12/2019

Boland CR & Goel A. Microsatellite instability in colorectal cancer. Gastroenterology. 2010;138(6):2073-2087.e3

T André et al. Pembrolizumab in Microsatellite-Instability-High Advanced Colorectal Cancer. N Engl J Med. 2020;383(23):2207-2218.

Cancer Council Australia. 2021. Understanding Immunotherapy. A guide for people affected by cancer.
Available at: https://www.cancer.org.au/assets/pdf/understanding-immunotherapy-fact-sheet
Accessed on 02/06/2022

National Cancer Institute. Biomarker Testing for Cancer Treatment.
Available at: https://www.cancer.gov/about-cancer/treatment/types/biomarker-testing-cancer-treatment
Accessed on 23/01/2024

Ministry of Health. 2018. Molecular Testing of Colorectal Cancers in New Zealand: Minimum standards for molecular testing of newly diagnosed colorectal cancers. Wellington: Ministry of Health.

Te Whatu Ora – Health New Zealand. 2023. Clinical Practice Guidelines for Bowel Screening in New Zealand. Wellington: Te Whatu Ora – Health New Zealand.

KEYTRUDA Data Sheet

KEYTRUDA Consumer Medicine Information

Cancer Council Australia. 2021. 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 15/10/2023

Cancer Council Australia. 2022. Understanding Kidney 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 04/10/2023

NZ-KEY-00881. TAPS DA 2339KN TAPS NP20132. First Issued February 2024.