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Pembrolizumab (Keytruda)

Pembrolizumab (pronounced pem-bro-lee-zoo-mab) is a type of immunotherapy. It is also known by its brand name, Keytruda. 

You might have it as a treatment for: 

  • non small cell lung cancer (NSCLC)
  • melanoma skin cancer
  • bladder cancer
  • Hodgkin lymphoma

You might also have pembrolizumab as part of a clinical trial for another type of cancer. 

How pembrolizumab works

Pembrolizumab is a type of immunotherapy. It stimulates the body's immune system to fight cancer cells. 

Pembrolizumab targets and blocks a protein called PD-1 on the surface of certain immune cells called T-cells. Blocking PD-1 triggers the T-cells to find and kill cancer cells.

How you have pembrolizumab

You have pembrolizumab as a drip into a vein (intravenously).

Into your bloodstream

You have the treatment through a drip into your arm or hand. A nurse puts a small tube (a cannula) into one of your veins and connects the drip to it.

You might need a central line. This is a long plastic tube that gives the drugs into a large vein, either in your chest or through a vein in your arm. It stays in while you’re having treatment, which may be for a few months.

When you have pembrolizumab

You usually have pembrolizumab every 3 weeks. It takes about 30 minutes each time you have it. You have pembrolizumab for as long as it works and the side effects are not too bad. You usually have it for up to 2 years, but some people might have treatment for longer than 2 years.

Depending on your cancer type, you might have pembrolizumab on its own or with other cancer treatments. 

Tests

You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

Side effects

We haven't listed all the side effects. It is very unlikely that you will have all of these side effects, but you might have some of them at the same time.

How often and how severe the side effects are can vary from person to person. They also depend on what other treatment you are having. For example, your side effects could be worse if you are also having other drugs or radiotherapy.

This treatment affects the immune system. This may cause inflammation in different parts of the body which can cause serious side effects. They could happen during treatment, or some months after treatment has finished. In some people, these side effects could be life threatening.

When to contact your team

Your doctor or nurse will go through the possible side effects. They will monitor you closely during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

  • you have severe side effects
  • your side effects aren’t getting any better
  • your side effects are getting worse

Early treatment can help manage side effects better. 

Contact your doctor or nurse immediately if you have signs of infection, including a temperature above 37.5C or below 36C.

Common side effects

These side effects happen in more than 10 in 100 people (10%). You might have one or more of them. They include:

Feeling or being sick (nausea)

Feeling or being sick is usually well controlled with anti sickness medicines. Avoiding fatty or fried foods, eating small meals and snacks, drinking plenty of water, and relaxation techniques, can all help.

Skin changes

You might notice skin changes, such as dryness, itching and rashes similar to acne on your face, neck and trunk. 

Tell your doctor if you have any rashes or itching. Don't go swimming if you have a rash because the chlorine in the water can make it worse.

If your skin gets dry or itchy, smoothing in unperfumed moisturising cream may help. Check with your doctor or nurse before using any creams or lotions. Wear a high factor sun block if you’re going out in the sun.

Breathlessness

You might be breathless and look pale due to a drop in red blood cells. This is called anaemia.

You may also be breathless and have a cough. This could be due to infection, such as pneumonia or inflammation of the lungs (pneumonitis). Let your doctor or nurse know straight away if you suddenly become breathless or develop a cough.

Low levels of thyroid hormones

The level of your thyroid hormones may drop (hypothyroidism). You may feel tired or cold, gain weight, feel sad or depressed, or your voice may deepen. You will have regular blood tests to check your thyroid hormone levels.

Loss of appetite

You might lose your appetite for various reasons when you are having cancer treatment. Sickness, taste changes or tiredness can put you off food and drinks.

Headaches

Tell your doctor or nurse if you keep getting headaches. They can give you painkillers to help.

Diarrhoea or constipation

Tell your doctor or nurse if you have diarrhoea or constipation. They can give you medicine to help. 

Pain

You might have pain in different parts of your body such as the tummy (abdomen), muscles, joints and back. Let your doctor or nurse know if you have pain during or after treatment. There are lots of ways to treat pain, including relaxation and painkillers. 

Fatigue

You might feel very tired and as though you lack energy.

Various things can help you to reduce tiredness and cope with it, for example exercise. Some research has shown that taking gentle exercise can give you more energy. It is important to balance exercise with resting.

Fluid build up

You may have swelling of your face, hands and legs due to a build up of fluid (oedema). 

High temperature

If you get a high temperature, let your treatment team know straight away. Ask them if you can take paracetamol to help lower your temperature.

Occasional side effects

These side effects happen in between 1 and 10 out of every 100 people (1%). You might have one or more of them. They include:

  • a drop in the number of white blood cells and platelets in your body which may increase your risk of infection and cause bruising and bleeding
  • inflammation of the bowel (colitis) which can cause diarrhoea and tummy pain
  • an allergic reaction to pembrolizumab. Some reactions can be severe and life threatening
  • high levels of thyroid hormones causing anxiety, difficulty sleeping and weight loss
  • low levels of minerals and salts in your body such as sodium, potassium and calcium
  • difficulty sleeping
  • dizziness
  • taste changes
  • numbness or tingling in your hands and feet
  • dry eyes and mouth
  • heart changes such as an abnormal heart rhythm and high blood pressure
  • hair loss
  • severe skin reactions and changes to your skin colour
  • swelling in your joints
  • chills and flu like symptoms
  • liver changes that are usually mild and unlikely to cause any symptoms

Rare side effects

These side effects happen in fewer than 1 in 100 people (1%). You might have one or more of them. They include:

  • break down of red blood cells in your body which can cause yellowing of the skin and eyes, dark coloured urine and high temperature (fever)
  • a condition where cells in your body clump together to make lumps. This usually affects your lungs and skin
  • inflammation in different organs of your body including thyroid, pituitary gland, liver, kidneys and pancreas
  • damage to the adrenal gland which can cause a drop in the level of certain hormones such as cortisol
  • high levels of glucose in your body (type 1 diabetes)
  • seizures (fits)
  • a condition where your immune system attacks healthy nerve cells which can cause numbness, pain and weakness in your feet and hands
  • severe muscle weakness that worsens with physical exercise
  • inflammation of the eyes and brain
  • infection of the membranes that surround the brain and spinal cord (meningitis) which can be life threatening
  • inflammation of certain skin cells called melanocytes
  • a collection of fluid around your heart
  • a hole in your small bowel
  • a severe skin reaction that may start as tender red patches which leads to peeling or blistering of the skin. You might also feel feverish and your eyes may be more sensitive to light. This is serious and could be life threatening

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do I need to know?

Other medicines, foods and drink

Cancer drugs can interact with some other medicines and herbal products. Tell your doctor or pharmacist about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies.

Loss of fertility

It is not known whether this treatment affects fertility in people. Talk to your doctor before starting treatment if you think you may want to have a baby in the future.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment with this drug and for at least 4 months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.

Breastfeeding

Don’t breastfeed during this treatment because the drug may come through into your breast milk.

Treatment for other conditions

Always tell other doctors, nurses, pharmacists or dentists that you’re having this treatment if you need treatment for anything else, including teeth problems.

Immunisations

Don’t have immunisations with live vaccines while you’re having treatment and for up to 12 months afterwards. The length of time depends on the treatment you are having. Ask your doctor or pharmacist how long you should avoid live vaccinations.

In the UK, live vaccines include rubella, mumps, measles, BCG, yellow fever and the shingles vaccine (Zostavax).

You can:

  • have other vaccines, but they might not give you as much protection as usual
  • have the flu vaccine (as an injection)
  • be in contact with other people who have had live vaccines as injections

Avoid close contact with people who have recently had live vaccines taken by mouth (oral vaccines) such as oral polio or the typhoid vaccine.

This also includes the rotavirus vaccine given to babies. The virus is in the baby’s poo for up to 2 weeks and could make you ill. So avoid changing their nappies for 2 weeks after their vaccination if possible. Or wear disposable gloves and wash your hands well afterwards.

You should also avoid close contact with children who have had the flu vaccine nasal spray if your immune system is severely weakened. 

More information about this treatment

For further information about this treatment go to the electronic Medicines Compendium (eMC) website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

iWantGreatCare lets patients leave feedback on their experience of taking a particular drug. The feedback is from individual patients. It is not information, or specialist medical advice, from Cancer Research UK.

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