What is Phesgo® or pertuzumab and trastuzumab?

Pertuzumab and trastuzumab are used to treat breast cancer. Often a combined treatment called Phesgo® is used instead. Phesgo® contains pertuzumab, trastuzumab, and hyaluronidase-zzxf. It is best to read this information with our general information about breast cancer.

These treatments belong to a group of targeted therapy drugs known as monoclonal antibodies. They both work by targeting specific proteins (receptors).

Some breast cancers have too much of a protein called human epidermal growth factor receptor 2 (HER2) on the surface of their cells. These are called HER2 positive cancers. The extra HER2 receptors stimulate the cancer cells to divide and grow.

Phesgo® or pertuzumab and trastuzumab only work in people who have cancer with high levels of HER2. These drugs lock on to different parts of the HER2 proteins. This blocks the receptors and stops the cancer cells dividing and growing.

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

How Phesgo® or pertuzumab and trastuzumab is given

You will be given this treatment at a day unit as an outpatient. You may have these drugs in combination with chemotherapy. Our information about chemotherapy drugs explains the side effects you may get.

During treatment you usually see a cancer doctor, a cancer nurse or specialist nurse, and a specialist pharmacist. This is who we mean when we mention doctor, nurse or pharmacist in this information.

Before or on the day of treatment, a nurse or person trained to take blood (phlebotomist) will take a blood sample from you. This is to check that your blood cells are at a safe level to have treatment.

You will see a doctor or nurse at the clinic. They will ask you how you have been feeling. If your blood results are okay, the pharmacist will prepare your targeted therapy. Your nurse will tell you when your treatment is likely to be ready.

This treatment can be given as an injection under the skin (subcutaneous). Less commonly you have it as a drip into a vein (intravenous infusion).

As an injection under your skin

The most common way of having trastuzumab and pertuzumab together is as a combination of the 2 drugs called Phesgo®. You have this as an injection under the skin (subcutaneous) every 3 weeks. This is a much quicker and easier way of having these drugs than into a vein (intravenously).

The nurse gives you the injection under the skin, usually in your thigh, over several minutes. After the first injection, they monitor you for a reaction for 30 minutes. After further treatments you are monitored for 15 minutes. The nurses will give the next injection into the other thigh.

As a drip into a vein (intravenous infusion)

Trastuzumab and pertuzumab are not often given in this way, because Phesgo® is now available.

Your nurse will give you the treatment through a drip or infusion connected to a pump, so it is given over a set time. The treatment can be given through:

  • a short thin tube the nurse puts into a vein in your arm or hand (cannula)
  • a fine tube that goes under the skin of your chest and into a vein close by (central line)
  • a fine tube that is put into a vein in your arm and goes up into a vein in your chest (PICC line).
Some people may have a reaction to them, so both drugs are given slowly the first time. You stay in hospital for a few hours afterwards so the nurses can monitor you. If you have no problems with the first treatment, the following treatments can be given over a shorter time.

Your course of treatment

You have pertuzumab and trastuzumab or Phesgo® once every 3 weeks. This forms 1 cycle of treatment. They are usually given with chemotherapy to begin with.

You usually have a course of several cycles of treatment over a few months. Your nurse, pharmacist or doctor will discuss your treatment plan with you.

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

Some people may have side effects while they are being given this treatment or shortly after they have it:

Allergic reaction

Some people have an allergic reaction while having this treatment. Signs of a reaction can include:

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

Your nurse will check you for signs of a reaction during your treatment. If you feel unwell or have any of these signs, tell them straight away. If you do have a reaction, it can be treated 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 are having Phesgo® (pertuzumab and trastuzumab as an injection under the skin) you may have discomfort or redness in the injection area. This is usually mild and temporary.

Common side effects of pertuzumab and 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

This treatment can affect the way the heart works. Before you start treatment, your doctor will check your heart health and arrange some tests. You will have these tests again during and after treatment. If the tests show signs of heart changes or you develop symptoms of heart problems, these can be treated with tablets.

Sometimes the symptoms of heart problems are like the symptoms of other conditions. But it is best to get any new symptom checked by your doctor. Always tell your doctor if you:

  • have chest discomfort, pain or tightness
  • have pain that spreads to your arm, neck, jaw, stomach or back
  • have palpitations, which might feel like a thumping or fluttering in your chest
  • feel short of breath
  • have swelling of the feet, ankles, stomach or lower back
  • faint (have blackouts), or feel light-headed or dizzy.

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.

Feeling sick

It is not common to feel sick with this treatment. But you may feel sick in the first few hours or days after treatment.

Your doctor will give you anti-sickness drugs to help stop you from feeling sick. Take the drugs exactly as your nurse or pharmacist tells you.

If you feel sick, take small sips of fluids often and eat small amounts regularly. It is important to drink enough fluids. If you continue to feel sick, or if you are sick (vomit) more than once in 24 hours, contact the hospital as soon as possible. They will give you advice. Your doctor or nurse may change the anti-sickness drug to one that works better for you.

Tummy (abdominal) pain

You may feel pain or discomfort in your tummy (abdomen) or have indigestion. Your doctor can prescribe drugs to help improve these symptoms. Tell them if the pain doesn't improve or gets worse.

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.

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.

It is more common to have a sore mouth when you are having these drugs with chemotherapy. It will usually improve once you finish the chemotherapy.

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.

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.

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.

Effects on the lungs

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

  • a cough
  • wheezing
  • breathlessness.

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

Headaches

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

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.

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. If you have painkillers you would like to use at home, check with your doctor, nurse or pharmacist whether they are suitable for you.

If you have muscle or joint pain, try:

  • placing a heat pad or covered hot water bottle against the painful area
  • taking warm baths
  • planning your activities to include regular rests.

Watery, sore eyes

Your eyes may become watery. Sometimes they may become sore and inflamed (conjunctivitis). 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.

Difficulty sleeping

Sometimes this treatment can cause sleeplessness (insomnia). Tell your doctor if you find it difficult to sleep.

Dizziness

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

Other information

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.

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.

Breastfeeding

You are advised not to breastfeed while having this treatment, or for some time 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.

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 2022
|
Next review: 01 November 2024
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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