What is trastuzumab?

Trastuzumab belongs to a group of targeted therapy drugs known as monoclonal antibody. Trastuzumab is often given in combination with chemotherapy and other cancer drugs.

Some cancer cells have too much of a protein called HER2 – this is called HER2 positive cancer. HER2 encourages cancer cells to grow. Cells taken during a biopsy or surgery to remove the cancer are tested for HER2. 

Trastuzumab can be used to treat HER2 positive cancer. It works by locking on to the HER2 protein to help stop the cancer cells from dividing and growing.

It is best to read this information with our general information about the type of cancer you have.

Your doctor will talk to you about this treatment and its possible side effects before you agree (consent) to have treatment.

This information is not about: 

We have separate information about these treatments.

How is trastuzumab given?

You will be given trastuzumab at a day unit. It can be given on its own or in combination with other cancer drugs. 

During treatment, you usually see a:

  • cancer doctor
  • cancer nurse or a specialist nurse
  • specialist pharmacist.

This is who we mean when we mention doctor, nurse or pharmacist in this information.

You will have regular blood tests during treatment. These are to check: 

  • that your blood cells are at a safe level to have treatment 
  • your general health.

You will speak to a doctor, nurse or pharmacist before you have treatment. They will ask how you have been feeling. If your blood results are okay, the pharmacy team will prepare your targeted therapy.

Trastuzumab can be given as a drip into a vein (intravenous infusion) or as an injection under the skin (subcutaneous). Which one you have depends on your treatment plan.

You usually have trastuzumab once every 3 weeks.

As a drip

The nurses give you the first dose (infusion) slowly. This is usually over 1½ hours (90 minutes). For the first infusion, you stay in hospital for a few hours so they can monitor you for any reaction. 

If the first infusion does not cause a reaction, you can have the following ones over 30 to 90 minutes. Then you go home about 1 hour later. 

As an injection under the skin

A nurse gives you the injection under the skin on your thigh. This takes a few minutes. After the first injection, the nurse monitors you for a few hours to make sure you do not have a reaction. If the first injection does not cause a reaction, you can go home sooner after the following ones.

Your course of treatment

How long you have trastuzumab depends on your situation. Your doctor, nurse or pharmacist will talk to you about your treatment plan.

If the cancer is advanced, trastuzumab might be given for as long as it is controlling the cancer.

About side effects

About side effects

We explain the most common side effects of this treatment here. We also include some less common side effects.

You may get some of the side effects we mention, but you are unlikely to get all of them. If you are also having treatment with other cancer drugs, you may have some side effects that we have not listed here.

You may have some rarer side effects that we have not listed here. Always tell your doctor, nurse or pharmacist about any side effects you have.

Your doctor, nurse or pharmacist can give you drugs to help control some side effects. It is important to take them exactly as they tell you. This means the drugs will be more likely to work for you. Your doctor, nurse or pharmacist will give you advice about managing your side effects. After your treatment is over, most side effects start to improve.

Serious and life-threatening side effects

Some cancer treatments can cause severe side effects. Rarely, these may be life-threatening. Your cancer doctor or nurse can explain the risk of these side effects to you.

Contact the hospital

Your nurse will give you telephone numbers for the hospital. If you feel unwell or need advice, you can call them at any time of the day or night. Save these numbers in your phone or keep them somewhere safe.

More information

We cannot list every side effect for this treatment. There are some rare side effects that are not listed. You can visit the electronic Medicines Compendium (eMC) for more detailed information.

Side effects while treatment is being given

Allergic reaction

Some people have an allergic reaction to monoclonal antibody treatment while they are having it. The first infusion or injection is the most likely to cause a reaction. If you are having trastuzumab as an infusion, it is usually given more slowly than later treatments.

Before treatment, you may be given medicines to help prevent or reduce any reaction. Signs of a reaction can include:

  • feeling hot or flushed
  • shivering
  • itching
  • a skin rash
  • feeling dizzy or sick
  • a headache
  • feeling breathless or wheezy
  • swelling of your face or mouth
  • pain in your back, tummy (abdomen) or chest.

Your nurse will check you for signs of a reaction during and after your treatment. If you feel unwell or have any of these signs, tell them straight away. If you do have a reaction, they can treat it quickly.

Sometimes a reaction happens a few hours after treatment. If you develop any signs or feel unwell after you get home, contact the hospital straight away.

Problems at the injection site

If you have trastuzumab as an injection under the skin, you may have some stinging, redness or bruising in the injection area. This is usually mild and goes away soon. The nurse will swap between your left and right thigh to help prevent this.

Common side effects of trastuzumab

Risk of infection

This treatment can reduce the number of white blood cells in your blood. These cells fight infection. If the number of white blood cells is low, you are more likely to get an infection. A low white blood cell count is sometimes called neutropenia.

An infection can be very serious when the number of white blood cells is low. It is important to get any infection treated as soon as possible. Contact the hospital straight away on the 24-hour contact number you have been given if:

  • your temperature goes over 37.5°C (99.5°F)
  • you suddenly feel unwell, even with a normal temperature
  • you have symptoms of an infection
  • your temperature goes below 36°C (96.8°F).

Symptoms of an infection include:

  • feeling shivery and shaking
  • a sore throat
  • a cough
  • breathlessness
  • diarrhoea
  • needing to pass urine (pee) a lot, or discomfort when you pass urine.

It is important to follow any specific advice your cancer treatment team gives you.

You will have regular blood tests during treatment. If needed, your doctor may reduce or delay your treatment for a short time, until your cell count increases.

Bruising and bleeding

This treatment can reduce the number of platelets in your blood. Platelets are cells that help the blood to clot.

If the number of platelets is low, you may bruise or bleed easily. You may have:

  • nosebleeds
  • bleeding gums
  • heavy periods
  • blood in your urine (pee) or stools (poo)
  • tiny red or purple spots on the skin that may look like a rash.

Tell your doctor if you have any unexplained bruising or bleeding. You may need a drip to give you extra platelets. This is called a platelet transfusion.

Anaemia (low number of red blood cells)

This treatment can reduce the number of red blood cells in your blood. Red blood cells carry oxygen around the body. If the number of red blood cells is low, this is called anaemia. You may have symptoms such as:

  • pale skin
  • lack of energy
  • feeling breathless
  • feeling dizzy and light-headed.

Tell your doctor or nurse if you have these symptoms.

If you are very anaemic, you may need a drip to give you extra red blood cells. This is called a blood transfusion.

Effects on the heart

Trastuzumab can affect how the heart works. You will have tests to see how well your heart is working. These will be done before you start treatment, and at regular times during and after treatment.

If the treatment is causing heart problems, your doctor may make changes to your treatment.

Contact your doctor straight away on the 24-hour number the hospital has given you if you have any of these symptoms during or after treatment:

  • pain or tightness in your chest
  • breathlessness or a cough
  • build-up of fluid (swelling) in the legs or arms
  • dizziness
  • changes to your heartbeat.

Other conditions can cause these symptoms, but it is important to get them checked by a doctor. If you cannot get through to your doctor, call the NHS urgent advice number on 111.

Feeling sick

This is usually mild, but your doctor can prescribe drugs to reduce sickness or vomiting. Tell your doctor if it does not get better.

Sore mouth and throat

This treatment may cause a sore mouth and throat. You may also get mouth ulcers. This can make you more likely to get a mouth or throat infection. Use a soft toothbrush to clean your teeth or dentures in the morning, at night and after meals.

If your mouth or throat is sore:

  • tell your nurse or doctor – they can give you a mouthwash or medicines to help
  • try to drink plenty of fluids
  • avoid alcohol, tobacco, and foods that irritate your mouth and throat.

Sucking ice chips may sometimes help relieve mouth or throat pain. But if you are having radiotherapy to the head or neck, do not suck on ice. It can cause damage.

Loss of appetite

This treatment can affect your appetite. Don't worry if you do not eat much for a day or 2. But if your appetite does not come back after a few days, or if you are losing weight, tell your nurse or dietitian. They can give you advice. They may give you food or drink supplements. Or they may suggest changes to your diet or eating habits to help.

Changes to your taste

You may get a bitter or metal taste in your mouth. Sucking sugar-free sweets may help with this. Some foods may taste different or have no taste. Try different foods to find out what tastes best to you. Taste changes usually get better after treatment finishes. Your nurse can give you more advice.

Tummy pain

You may get pain in your tummy (abdomen), or have indigestion. Your doctor can give you drugs to help improve these symptoms. Tell them if the pain gets worse or does not get better.

Diarrhoea

This treatment may cause diarrhoea. Diarrhoea means passing more stools (poo) than is usual for you, or having watery or loose stools. If you have a stoma, it will be more active than usual.

If you have diarrhoea:

  • try to drink at least 2 litres (3½ pints) of fluids each day
  • avoid alcohol, caffeine, milk products, high-fat foods and high-fibre foods
  • contact the hospital for advice.

Constipation

This treatment can cause constipation. Constipation means that you are not able to pass stools (poo) as often as you normally do. It can become difficult or painful. Here are some tips that may help:

  • Drink at least 2 litres (3½ pints) of fluids each day.
  • Eat high-fibre foods, such as fruit, vegetables and wholemeal bread.
  • Do regular gentle exercise, like going for short walks.

If you have constipation, contact the hospital on the 24-hour number for advice. They can give you drugs called laxatives to help. 

If you have not been able to pass stools for over 2 days and are being sick, contact the 24-hour number straight away. 

Headaches

This treatment may cause headaches. If you have headaches, tell your doctor. They may give you painkillers to help.

Muscle or joint pain

You may get pain in your muscles or joints for a few days after treatment. If this happens, tell your doctor so they can give you painkillers. Tell them if the pain does not get better. Having warm baths and taking regular rests may help.

Hot flushes

You may have hot flushes and sweats while having trastuzumab.

Watery, sore eyes

Your eyes may become watery. Sometimes they may become sore and inflamed (conjunctivitis). Tell your doctor or nurse if you notice any changes in your eyes or vision. Your doctor can prescribe eye drops if you need them. 

Blocked or runny nose, or nose bleeds

These side effects are not usually serious. But if you have any of them, tell your doctor or nurse. They may be able to help if you find the side effects difficult to cope with.

Numb or tingling hands or feet (peripheral neuropathy)

This treatment may affect the nerves, which can cause numb, tingling or painful hands or feet. You may find it hard to fasten buttons or do other fiddly tasks.

Tell your doctor if you have these symptoms. They sometimes need to lower the dose of the drug. The symptoms usually improve slowly after treatment finishes. But for some people they may never go away. Talk to your doctor if you are worried about this.

Skin or nail changes

This treatment may affect your skin. It may cause a rash, which might be itchy. Your doctor or nurse can tell you what to expect. If your skin feels dry, try using an unperfumed moisturising cream every day. 

Always tell your doctor or nurse about any changes to your skin. They can give you advice and may prescribe creams or medicines to help. Skin changes usually improve when treatment finishes.

Your nails also might become brittle and break easily. If this happens, wear gloves when washing dishes or using detergents to help protect your nails.

Hair loss

Your hair may get thinner. But you are unlikely to lose all the hair from your head. Hair loss usually starts after your first or second treatment. It is almost always temporary, and your hair will usually grow back after treatment finishes. Your nurse can talk to you about ways to cope with hair loss.

Sore and red palms of hands and soles of feet

You may get sore and red palms of hands and soles of feet. The skin may also begin to peel. This is called palmar-plantar or hand-foot syndrome. It usually gets better after treatment ends.

Tell your doctor or nurse about any changes to your hands or feet. They can give you advice and prescribe creams to improve any symptoms you have. It can help to:

  • keep your hands and feet cool
  • moisturise your hands and feet regularly
  • avoid tight-fitting socks, shoes and gloves.

Difficulty sleeping

This treatment can cause sleeping problems (insomnia). If you are finding it difficult to sleep, talk to your nurse or doctor.

Feeling tired

Feeling tired is a common side effect of this treatment. It is often worse towards the end of treatment and for some weeks after it has finished. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can give you more energy.

If you feel sleepy, do not drive or use machinery.

Mood changes

You may have some mood changes during this treatment. You may feel low or depressed. Let your doctor or nurse know if you notice any changes.

Dizziness

If you feel dizzy or drowsy, tell your doctor. It is important not to drive or operate machinery if you feel this way.

Effects on the lungs

This treatment can cause changes to the lungs. Tell your doctor if you develop:

  • a cough
  • wheezing
  • a fever (high temperature)
  • breathlessness.

You should also tell them if any existing breathing problems get worse. You may have tests to check your lungs.

If your symptoms develop suddenly, contact the hospital immediately. You may have inflammation of the lungs (pneumonitis). Your doctor can tell you more about this.

Effects on the kidneys

This treatment can affect how your kidneys work. This is usually mild and goes back to normal after treatment finishes. You will have blood tests to check how well your kidneys are working. Tell your doctor or nurse if you have blood in your urine (pee) or you are passing urine less than usual.

It is important to drink at least 2 litres (3½ pints) of non-alcoholic fluid each day to help protect your kidneys.

Effects on the liver

This treatment may affect how your liver works. This is usually mild. You will have blood tests to check how well your liver is working.

Other information about trastuzumab

Blood clot risk

Cancer and some cancer treatments can increase the risk of a blood clot. Contact the hospital straight away on the 24-hour number if you have any of these symptoms during or after treatment:

  • throbbing pain or swelling in a leg or arm
  • reddening of the skin in the area – if you have black or brown skin, this can be harder to notice, but the skin might become darker
  • suddenly feeling breathless or coughing.

Always call 999 if you have:

  • chest pain
  • difficulty breathing.

A blood clot is serious, but it can be treated with drugs called anticoagulants. These thin the blood. Your doctor, nurse or pharmacist can give you more information about preventing and treating blood clots.

Other medicines

Some medicines can affect how this treatment works or be harmful while you are having it. Always tell your cancer doctor, nurse or pharmacist about any drugs you are taking or planning to take, such as: 

Vaccinations

Vaccinations can reduce your risk of getting certain infections. Your doctor or nurse may talk to you about having vaccinations.

Doctors usually recommend that people with cancer have a flu vaccination and a coronavirus (covid) vaccination. These are both inactivated vaccinations that can help reduce the risk of infection. People with weak immune systems can have these, as they are not live vaccinations. 

If your immune system is weak, you need to avoid live vaccinations. This is because they can make you unwell. Live vaccines contain a very weak version of the illness they are vaccinating you against. Your cancer doctor or GP can tell you more about live and inactivated vaccinations.

Contraception

Your doctor will advise you not to get pregnant or make someone pregnant while having this treatment. The drugs may harm a developing baby. It is important to use contraception during your treatment and for a while after treatment finishes. Your doctor, nurse or pharmacist can tell you more about this.

Breastfeeding

You are advised not to breastfeed while having this treatment, or for at least 7 months after treatment finishes. This is because the drugs could be passed to the baby through breast milk. 

Your doctor or nurse can give you more information.

Fertility

Some cancer drugs can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor before you start treatment.

Medical and dental treatment

If you need medical treatment for any reason other than cancer, always tell the doctors and nurses you are having cancer treatment. Give them the contact details for your cancer doctor so they can ask for advice.

If you think you need dental treatment, talk to your cancer doctor or nurse. Always tell your dentist you are having cancer treatment.

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert health professionals and people living with cancer.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 May 2023
|
Next review: 01 May 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

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