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Colorectal Cancer

A headshot of a grey-haired woman of South Asian descent, sitting in a wheelchair and smiling softly at the camera.

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.

Click here to read about cancer staging

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.

Click here to learn more about KEYTRUDA

Glossary

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

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

Read more >
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Patient Resources

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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.

KEYTRUDA® (pembrolizumab) 100 mg/4 mL concentrate solution for infusion is a Prescription Medicine. KEYTRUDA has risks and benefits. The KEYTRUDA Consumer Medicine Information (CMI) is available at www.medsafe.govt.nz or by clicking the 'Consumer Medicine Information' button at the top of this page.

IMPORTANT SAFETY INFORMATION

You should not be given KEYTRUDA if you are allergic to pembrolizumab or to any of the following inactive ingredients: histidine, histidine monohydrochloride monohydrate, sucrose, polysorbate-80, water for injection.

Tell your doctor if you have a disease of your immune system such as Crohn’s disease, ulcerative colitis, or lupus; have had an organ transplant or have had a bone marrow (stem cell) transplant that used donor stem cells (allogeneic); have pneumonia or swelling of your lungs (called pneumonitis); or have liver problems.

If you are pregnant, think you may be pregnant or are planning to have a baby, tell your doctor. KEYTRUDA can cause harm or death to your unborn baby. Effective contraception must be used during treatment with KEYTRUDA and for at least 4 months after the last dose of KEYTRUDA for woman who could become pregnant.

If you are breastfeeding, tell your doctor. Do not breastfeed while taking KEYTRUDA.

Tell your doctor if you are taking any other medicines, including medicines that can be bought without a prescription from a pharmacy, supermarket or health food shop, or other medicines that make the immune system weak. Examples of these may include steroids, such as prednisone.

What are the possible side effects of KEYTRUDA?

KEYTRUDA can have some serious side effects. These side effects can sometimes become life-threatening and can lead to death. These side effects may happen any time during treatment or even after treatment has ended. More than one side effect can be experienced at the same time.

Call or see your doctor right away if you develop any of the following symptoms:

Lung problems:
Signs and symptoms of lung problems may include shortness of breath, chest pain, or coughing.

Intestinal problems:
Signs and symptoms of problems with your intestines may include diarrhoea or more bowel movements than usual, stools that are black, tarry, sticky, or have blood or mucus, or severe stomach pain or tenderness.

Liver problems:
Signs and symptoms of liver problems may include nausea or vomiting, feeling less hungry, pain on the right side of your stomach, your skin looks yellow, the whites of your eyes look yellow, dark urine or you bleed or bruise more easily than normal.

Hormone gland problems (especially the thyroid, pituitary, adrenal glands):
Signs and symptoms of hormone gland problems may include rapid heartbeat, weight loss or weight gain, increased sweating, hair loss, feeling cold, constipation, your voice gets deeper, muscle aches, dizziness or fainting, or headaches that will not go away or unusual headache.

Kidney problems:
Signs and symptoms of kidney problems may include change in the amount or colour of your urine.

Blood sugar problems:
Signs and symptoms of blood sugar problems may include feeling more hungry or thirsty, needing to urinate more often or weight loss.

Skin problems:
Signs and symptoms of skin problems may include rash, itching, blisters, peeling or skin sores, or ulcers in mouth or in lining of nose, throat, or genital area.

Problems in other organs:
Signs and symptoms of problems in other organs may include muscle pain or weakness; changes in eyesight; stomach area pain with nausea and vomiting (pancreatitis); shortness of breath, irregular heartbeat, feeling tired, or chest pain (myocarditis, pericarditis); confusion, fever, memory problems, or seizures (encephalitis); swollen lymph nodes, rash or tender lumps on skin, cough, or eye pain (sarcoidosis); pain, numbness, tingling, or weakness in the arms or legs, bladder or bowel problems including needing to urinate more frequently, urinary incontinence, difficulty urinating and constipation (myelitis); inflammation of the blood vessels (vasculitis); decreased function of the parathyroid gland, which may include muscle cramps or spasms, fatigue and weakness (hypoparathyroidism); inflammation of the stomach lining, which may include severe stomach pain or tenderness, nausea or vomiting (gastritis); destruction of red blood cells, which may include dark urine, pale or yellow skin/eyes, lightheadedness, feeling tired, rapid heartbeat, or shortness of breath (haemolytic anaemia), or pain in the upper right part of the stomach, swelling of the liver or spleen, fatigue, itching or yellowing of the skin or whites of eyes (sclerosing cholangitis) ; or decreased ability of the pancreas to make digestive enzymes, which may include diarrhoea with loose and oily stools, weight loss, metabolic bone disease, and vitamin or mineral deficiencies (exocrine pancreatic insufficiency).

Infusion (IV) reactions:
Signs and symptoms of infusion reactions may include shortness of breath, itching or rash, dizziness or fever.

Rejection of a transplanted organ:
People who have had an organ transplant may have an increased risk of organ transplant rejection. Your doctor should tell you what signs and symptoms you should report and monitor you, depending on the type of organ transplant that you have had.

Graft-versus-host-disease (GVHD) in people with bone marrow (stem cell) transplant that uses donor stem cells (allogeneic):
GVHD may occur if you had this transplant in the past. Your doctor will monitor you for the following signs and symptoms: skin rash, liver inflammation, abdominal pain, and diarrhoea.

Common side effects:
Common side effects (may affect more than 1 in 10 people) include: diarrhoea, nausea, itching, rash, joint pain, back pain, feeling tired, cough, patches of skin which have lost colour, stomach pain, decreased sodium levels in the blood and low levels of thyroid hormone.

Common side effects (reported in more than 1 in 5 people) when KEYTRUDA was given in combination with chemotherapy include: hair loss, feeling tired, diarrhoea, vomiting, rash, fever, decrease in white blood cell count, decreased appetite, joint pain, swelling of the lining of the digestive system (for example mouth, intestines), mouth sores, decrease in number of red blood cells and decrease in number of platelets in the blood.

The most common side effects when KEYTRUDA is given in combination with axitinib are: diarrhoea, high blood pressure, fatigue, low levels of thyroid hormone, decreased appetite, blisters or rash on the palms of your hands or soles of your feet, nausea, increase in liver enzyme levels, hoarseness, cough and constipation.

The most common side effects when KEYTRUDA is given in combination with lenvatinib are: high blood pressure, diarrhoea, feeling tired, decreased appetite, low levels of thyroid hormone, nausea, vomiting, weight loss, joint pain, headache, constipation, hoarseness, urinary tract infection, stomach-area (abdominal) pain, blisters or rash on the palms of your hands and soles of your feet, rash, protein in your urine, increase in liver enzyme levels and feeling weak.

The most common side effects when KEYTRUDA is given alone to children are: fever, vomiting, headache, stomach pain, decrease in number of red blood cells, cough, and constipation.

Less common side effects can happen. KEYTRUDA may cause other side effects that are not listed. If you have any side effect that bothers you or that does not go away, tell your doctor.

For more information, please talk to your doctor.

KEYTRUDA may be used to treat certain adults with the following types of advanced cancers:

  • melanoma
  • non-small cell lung cancer
  • urothelial carcinoma
  • classical Hodgkin Lymphoma
  • head and neck squamous cell carcinoma
  • renal cell carcinoma
  • oesophageal carcinoma
  • cervical cancer
  • endometrial carcinoma
  • gastric or gastroesophageal junction adenocarcinoma
  • triple-negative breast cancer
  • cutaneous squamous cell carcinoma
  • a kind of cancer that can occur in any part of the body and is shown by a laboratory test to be microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR)
  • colon or rectal cancer that is shown by a laboratory test to be MSI-H or dMMR
  • Merkel cell carcinoma
  • biliary tract carcinoma
  • malignant pleural mesothelioma

KEYTRUDA may also be used in certain adults:

  • after surgery to remove melanoma, non-small cell lung cancer, or renal cell carcinoma to help prevent the cancer from coming back
  • before surgery to treat triple-negative breast cancer and then continued after surgery to help prevent the cancer from coming back
  • to treat bladder cancer which has not spread to nearby tissues but is at high-risk of spreading and where bladder removal is not preferred

KEYTRUDA may be used in children with classical Hodgkin lymphoma, Merkel cell carcinoma, malignant pleural mesothelioma, MSI-H or dMMR cancers, or after surgery to remove melanoma. It is not known if KEYTRUDA is safe and effective in children with MSI-H or dMMR cancer of the brain or spinal cord (central nervous system cancers).

KEYTRUDA may sometimes be given in combination with other anti-cancer medicines.

Based on the KEYTRUDA Consumer Medicines Information and Data Sheet dated 5th February 2025.

Ask your doctor if KEYTRUDA is right for you. If symptoms continue or you have side effects, see your doctor, pharmacist, or health professional.

KEYTRUDA is funded to treat certain patients with the following types of advanced cancers: melanoma, non-small cell lung cancer, MSI-H or dMMR colorectal cancer, triple-negative breast cancer, head and neck squamous cell carcinoma, urothelial carcinoma, and classical Hodgkin lymphoma - further restrictions apply. KEYTRUDA is not funded for the treatment of all other cancers listed above.

Ask your health professional about the cost of the medicine and any other medical fees that may apply.

Merck Sharp & Dohme (New Zealand) Limited, Level 3, 123 Carlton Gore Road, Newmarket, Auckland.

TAPS NP20132 TAPS DA 2419KN NZ-KEY-00885v12 Last updated March 2025

Copyright © 2025 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved.

KEYTRUDA® (pembrolizumab) 100 mg/4 mL concentrate solution for infusion is a Prescription Medicine. KEYTRUDA has risks and benefits. The KEYTRUDA Consumer Medicine Information (CMI) is available at www.medsafe.govt.nz or by clicking the 'Consumer Medicine Information' button at the top of this page.

IMPORTANT SAFETY INFORMATION

KEYTRUDA® (pembrolizumab) 100 mg/4 mL concentrate solution for infusion is a Prescription Medicine. KEYTRUDA has risks and benefits. The KEYTRUDA Consumer Medicine Information (CMI) is available at www.medsafe.govt.nz or by clicking the 'Consumer Medicine Information' button at the top of this page.

IMPORTANT SAFETY INFORMATION

You should not be given KEYTRUDA if you are allergic to pembrolizumab or to any of the following inactive ingredients: histidine, histidine monohydrochloride monohydrate, sucrose, polysorbate-80, water for injection.

Tell your doctor if you have a disease of your immune system such as Crohn’s disease, ulcerative colitis, or lupus; have had an organ transplant or have had a bone marrow (stem cell) transplant that used donor stem cells (allogeneic); have pneumonia or swelling of your lungs (called pneumonitis); or have liver problems.

If you are pregnant, think you may be pregnant or are planning to have a baby, tell your doctor. KEYTRUDA can cause harm or death to your unborn baby. Effective contraception must be used during treatment with KEYTRUDA and for at least 4 months after the last dose of KEYTRUDA for woman who could become pregnant.

If you are breastfeeding, tell your doctor. Do not breastfeed while taking KEYTRUDA.

Tell your doctor if you are taking any other medicines, including medicines that can be bought without a prescription from a pharmacy, supermarket or health food shop, or other medicines that make the immune system weak. Examples of these may include steroids, such as prednisone.

What are the possible side effects of KEYTRUDA?

KEYTRUDA can have some serious side effects. These side effects can sometimes become life-threatening and can lead to death. These side effects may happen any time during treatment or even after treatment has ended. More than one side effect can be experienced at the same time.

Call or see your doctor right away if you develop any of the following symptoms:

Lung problems:
Signs and symptoms of lung problems may include shortness of breath, chest pain, or coughing.

Intestinal problems:
Signs and symptoms of problems with your intestines may include diarrhoea or more bowel movements than usual, stools that are black, tarry, sticky, or have blood or mucus, or severe stomach pain or tenderness.

Liver problems:
Signs and symptoms of liver problems may include nausea or vomiting, feeling less hungry, pain on the right side of your stomach, your skin looks yellow, the whites of your eyes look yellow, dark urine or you bleed or bruise more easily than normal.

Hormone gland problems (especially the thyroid, pituitary, adrenal glands):
Signs and symptoms of hormone gland problems may include rapid heartbeat, weight loss or weight gain, increased sweating, hair loss, feeling cold, constipation, your voice gets deeper, muscle aches, dizziness or fainting, or headaches that will not go away or unusual headache.

Kidney problems:
Signs and symptoms of kidney problems may include change in the amount or colour of your urine.

Blood sugar problems:
Signs and symptoms of blood sugar problems may include feeling more hungry or thirsty, needing to urinate more often or weight loss.

Skin problems:
Signs and symptoms of skin problems may include rash, itching, blisters, peeling or skin sores, or ulcers in mouth or in lining of nose, throat, or genital area.

Problems in other organs:
Signs and symptoms of problems in other organs may include muscle pain or weakness; changes in eyesight; stomach area pain with nausea and vomiting (pancreatitis); shortness of breath, irregular heartbeat, feeling tired, or chest pain (myocarditis, pericarditis); confusion, fever, memory problems, or seizures (encephalitis); swollen lymph nodes, rash or tender lumps on skin, cough, or eye pain (sarcoidosis); pain, numbness, tingling, or weakness in the arms or legs, bladder or bowel problems including needing to urinate more frequently, urinary incontinence, difficulty urinating and constipation (myelitis); inflammation of the blood vessels (vasculitis); decreased function of the parathyroid gland, which may include muscle cramps or spasms, fatigue and weakness (hypoparathyroidism); inflammation of the stomach lining, which may include severe stomach pain or tenderness, nausea or vomiting (gastritis); destruction of red blood cells, which may include dark urine, pale or yellow skin/eyes, lightheadedness, feeling tired, rapid heartbeat, or shortness of breath (haemolytic anaemia), or pain in the upper right part of the stomach, swelling of the liver or spleen, fatigue, itching or yellowing of the skin or whites of eyes (sclerosing cholangitis) ; or decreased ability of the pancreas to make digestive enzymes, which may include diarrhoea with loose and oily stools, weight loss, metabolic bone disease, and vitamin or mineral deficiencies (exocrine pancreatic insufficiency).

Infusion (IV) reactions:
Signs and symptoms of infusion reactions may include shortness of breath, itching or rash, dizziness or fever.

Rejection of a transplanted organ:
People who have had an organ transplant may have an increased risk of organ transplant rejection. Your doctor should tell you what signs and symptoms you should report and monitor you, depending on the type of organ transplant that you have had.

Graft-versus-host-disease (GVHD) in people with bone marrow (stem cell) transplant that uses donor stem cells (allogeneic):
GVHD may occur if you had this transplant in the past. Your doctor will monitor you for the following signs and symptoms: skin rash, liver inflammation, abdominal pain, and diarrhoea.

Common side effects:
Common side effects (may affect more than 1 in 10 people) include: diarrhoea, nausea, itching, rash, joint pain, back pain, feeling tired, cough, patches of skin which have lost colour, stomach pain, decreased sodium levels in the blood and low levels of thyroid hormone.

Common side effects (reported in more than 1 in 5 people) when KEYTRUDA was given in combination with chemotherapy include: hair loss, feeling tired, diarrhoea, vomiting, rash, fever, decrease in white blood cell count, decreased appetite, joint pain, swelling of the lining of the digestive system (for example mouth, intestines), mouth sores, decrease in number of red blood cells and decrease in number of platelets in the blood.

The most common side effects when KEYTRUDA is given in combination with axitinib are: diarrhoea, high blood pressure, fatigue, low levels of thyroid hormone, decreased appetite, blisters or rash on the palms of your hands or soles of your feet, nausea, increase in liver enzyme levels, hoarseness, cough and constipation.

The most common side effects when KEYTRUDA is given in combination with lenvatinib are: high blood pressure, diarrhoea, feeling tired, decreased appetite, low levels of thyroid hormone, nausea, vomiting, weight loss, joint pain, headache, constipation, hoarseness, urinary tract infection, stomach-area (abdominal) pain, blisters or rash on the palms of your hands and soles of your feet, rash, protein in your urine, increase in liver enzyme levels and feeling weak.

The most common side effects when KEYTRUDA is given alone to children are: fever, vomiting, headache, stomach pain, decrease in number of red blood cells, cough, and constipation.

Less common side effects can happen. KEYTRUDA may cause other side effects that are not listed. If you have any side effect that bothers you or that does not go away, tell your doctor.

For more information, please talk to your doctor.

KEYTRUDA may be used to treat certain adults with the following types of advanced cancers:

KEYTRUDA may also be used in certain adults:

KEYTRUDA may be used in children with classical Hodgkin lymphoma, Merkel cell carcinoma, malignant pleural mesothelioma, MSI-H or dMMR cancers, or after surgery to remove melanoma. It is not known if KEYTRUDA is safe and effective in children with MSI-H or dMMR cancer of the brain or spinal cord (central nervous system cancers).

KEYTRUDA may sometimes be given in combination with other anti-cancer medicines.

Based on the KEYTRUDA Consumer Medicines Information and Data Sheet dated 5th February 2025.

Ask your doctor if KEYTRUDA is right for you. If symptoms continue or you have side effects, see your doctor, pharmacist, or health professional.

KEYTRUDA is funded to treat certain patients with the following types of advanced cancers: melanoma, non-small cell lung cancer, MSI-H or dMMR colorectal cancer, triple-negative breast cancer, head and neck squamous cell carcinoma, urothelial carcinoma, and classical Hodgkin lymphoma - further restrictions apply. KEYTRUDA is not funded for the treatment of all other cancers listed above.

Ask your health professional about the cost of the medicine and any other medical fees that may apply.

Merck Sharp & Dohme (New Zealand) Limited, Level 3, 123 Carlton Gore Road, Newmarket, Auckland.

TAPS NP20132 TAPS DA 2419KN NZ-KEY-00885v12 Last updated March 2025

Copyright © 2025 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved.

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