1. What is pertuzumab and trastuzumab (Phesgo)?
Pertuzumab and trastuzumab are 2 targeted therapy drugs. When they’re given together, you may hear them called by their brand name Phesgo.
2. Who might be offered Phesgo?
Phesgo can be used to treat HER2-positive:
- that cannot be removed by surgery
You will only be offered Phesgo if your breast cancer is HER2-positive.
If your breast cancer is HER2-negative, Phesgo will not be of any benefit to you.
3. Before starting Phesgo
Before starting your treatment, a member of your treatment team will discuss how and when you’ll have Phesgo and how side effects can be managed.
You’ll have blood tests and your height and weight will be measured.
You will also have tests to check your heart function, such as:
- An
- An echocardiogram
This is because there is a chance that Phesgo can cause changes to the heart muscle. You will have an echocardiogram every 3 months during your treatment with Phesgo to monitor your heart function.
4. How Phesgo is given
Phesgo is usually given as an injection under the skin. You will usually have it every 3 weeks.
The first injection will take around 8 minutes. This is called a loading dose.
All other injections of Phesgo will take around 5 minutes.
You will have the injection in your thigh. Your treatment team may vary which thigh to inject.
Primary and locally advanced breast cancer
You will have Phesgo injections alongside to begin with. You will then continue to have Phesgo injections on their own.
You may have Phesgo for up to 1 year. However, your treatment team will discuss this with you in more detail.
Secondary breast cancer
If you have secondary breast cancer, you will usually have Phesgo injections with a chemotherapy drug (docetaxel or paclitaxel) to begin with. You will then continue to have Phesgo injections once you have finished your chemotherapy cycles.
You will have Phesgo injections for as long as your treatment team feels you’re benefiting from the drug and any side effects are manageable.
5. Side effects of Phesgo
Like any treatment, Phesgo can cause side effects. Everyone reacts differently to drugs and some people have more side effects than others. These side effects can usually be managed and those described here will not affect everyone.
As Phesgo can be given in addition to chemotherapy, it’s sometimes difficult to know which side effects are being caused by which treatment.
You should be given a 24-hour contact number or told who to contact if you feel unwell at any time during your treatment, including overnight or at the weekends.
If you’re worried about any side effects, regardless of whether they’re listed here, talk to your chemotherapy nurse or treatment team.
Common side effects
Effects on the blood
Phesgo given with chemotherapy can temporarily affect the number of blood cells in the body. Blood is made up of red cells, white cells and platelets.
You’ll have regular blood tests. If these show the number of blood cells is too low, your next cycle of treatment may be delayed or the dose of reduced.
Your treatment team may change the dose of a drug to suit you and help manage its side effects. This may help you stay on the treatment for longer.
Risk of infection
Not having enough white blood cells can increase your risk of getting an infection.
Signs of an infection
Your treatment team may give you advice on reporting signs of an infection. But generally you should contact your hospital immediately if you have any of the following:
- A high temperature (over 37.5°C) or low temperature (under 36°C)
- Suddenly feeling unwell, even with a normal temperature
- Symptoms of an infection, such as a sore throat, cough, needing to pee often or feeling cold or shivery, even if you do not have a high temperature
Before starting Phesgo you should be given a 24-hour contact number or told who to contact if you feel unwell at any time during your treatment, including overnight or at the weekends.
You may need treatment if you get an infection.
Sometimes your treatment team may recommend injections of drugs called growth factors. This helps the body make more white blood cells to reduce your risk of infection.
Before starting Phesgo you should be given a 24-hour contact number or told who to contact if you feel unwell at any time during your treatment, including overnight or at the weekends.
You may need treatment if you get an infection.
Sometimes your treatment team may recommend injections of drugs called growth factors. This helps the body make more white blood cells to reduce your risk of infection.
Anaemia
Having too few red blood cells is called anaemia. If you feel breathless, dizzy or particularly tired, let your treatment team know.
Bruising and bleeding
Phesgo can reduce the number of platelets. Platelets help the blood to clot.
If your platelets are low, you may:
- Bruise more easily
- Have nosebleeds
- Notice your gums may bleed when you brush your teeth
- Take longer to stop bleeding if you cut yourself
Tell your treatment team if you have any of these symptoms.
Heart changes
Phesgo may weaken the heart muscle. This is usually temporary, but for a small number of people it may be permanent.
Contact your treatment team if you develop:
- Breathlessness
- Chest pain
- Changes to your heartbeat, such as it beats very quickly, flutters or feels like you’ve missed a heartbeat
- Swollen ankles
As mentioned above, you will continue to have heart function tests every 3 months during treatment.
Diarrhoea or constipation
You may have diarrhoea or constipation. Your treatment team or GP can prescribe medicine to help control it.
Contact your team if you have diarrhoea 3 or more times in 24 hours.
Damage to the lungs
Phesgo can cause interstitial lung disease (ILD). ILD can cause inflammation in your lungs, which can lead to scarring.
If Phesgo has caused inflammation to your lungs, you may need to stop treatment temporarily to prevent further damage. You may have steroids to treat the inflammation.
Contact your treatment team or the 24-hour number straight away if you have:
- Shortness of breath
- A cough, with or without a high temperature
- Any new or worsening breathing problems, such as chest tightness or wheezing
These symptoms could have a number of causes including side effects of treatment or a lung infection. It’s important to let your treatment team know so that they can find out the cause. You may need a chest x-ray or CT scan to check what’s causing your symptoms.
Extreme tiredness (cancer-related fatigue)
Fatigue is extreme tiredness or exhaustion that doesn’t go away with rest or sleep. It’s a common side effect of breast cancer and its treatments. It may last for weeks, months or longer after your treatment has finished.
Cancer-related fatigue is also one of the most common symptoms in people with secondary breast cancer.
If you think you have fatigue, tell your GP or treatment team. They can assess you and offer advice on how to manage your energy levels.
Find out more about managing fatigue.
Nausea and vomiting
You may feel sick (nausea) and think you might be sick (vomit), but most people will not actually be sick.
Your treatment team will prescribe you anti-sickness drugs to take home to reduce nausea or stop it happening. If you continue to feel sick or vomit, tell your treatment team as they may be able to change your anti-sickness drugs.
Hand-foot syndrome (palmar-plantar erythrodysesthesia)
You may develop soreness or redness on the palms of your hands and soles of your feet. This is called palmar-plantar or hand-foot syndrome.
Redness can be harder to see on black or brown skin.
Your treatment team or GP can prescribe creams or medication to treat hand-foot syndrome.
Loss of appetite
You may lose your appetite.
Eating small frequent meals or snacks can help keep up your food intake.
If you’re concerned about how much you’re eating and drinking, ask your GP or specialist about being referred to a dietitian.
Find out more about diet and breast cancer treatment.
Sore mouth
Looking after your mouth, including your teeth and gums, is very important during treatment.
You’ll be given mouthwash to try to reduce soreness and stop mouth ulcers developing.
Numbness and tingling in the hands or feet (peripheral neuropathy)
You may have pain, numbness or tingling in the hands and feet (peripheral neuropathy). This is because Phesgo can affect the nerves.
For some people the symptoms stay mild and go away soon after treatment stops. However, for most people, the symptoms will gradually improve over the weeks and months after treatment has finished.
If you have symptoms of peripheral neuropathy, tell your treatment team so they can monitor your symptoms.
Joint or muscle pain
Sometimes you may have joint, jaw or muscle pain. Let your treatment team know if this happens. They may prescribe medication for pain relief.
Hair loss
Phesgo may cause hair loss, especially if you’re having it alongside chemotherapy.
Other common side effects
Other common side effects of Phesgo include:
- Difficulty sleeping
- Inflammation around the injection site
- Taste changes
- Headaches
- Indigestion
- Cold and flu-like symptoms
- Skin rash and nail problems
- Eye problems
- Shaky hands
If you’re worried about any side effects, regardless of whether they’re listed here, talk to your chemotherapy nurse or treatment team.
Less common side effects
Less common side effects of Phesgo include:
- Feeling anxious or depressed
- Swollen veins near your back passage (piles or haemorrhoids). This can be painful when you poo, so let your team know if you have this
- Dry mouth
- Changes to the way your kidneys work – you’ll have regular blood tests to check this
- Swollen or sore breasts
- Liver problems that are mild – you might have tummy pain, or yellowing of the skin or whites of the eyes (jaundice), but this is rare
- Sweating more than normal for you
Rare side effects
Cytokine release syndrome
This is where the drugs stimulate the immune system to make large amounts of a group of proteins called cytokines.
Symptoms include:
- High temperature
- Chills
- Headache
- Difficulty breathing
- Dizziness
6. Other important information
Allergic reaction
Having an allergic reaction to Phesgo is rare.
If you do have an allergic reaction, it’s more likely to happen within the first few minutes of your first or second treatment.
You’ll be monitored closely so any reaction can be dealt with immediately.
If you have a severe reaction, treatment will be stopped immediately.
If you have a less severe reaction, you may need to take medication before future treatments to reduce the risk of further reactions.
Contact your hospital immediately if you notice any of the following symptoms:
- Itchy red or discoloured bumps on your skin (these may be harder to see on black or brown skin)
- Swelling in your lips, tongue or throat
- Breathlessness, wheezing, a bad cough or sudden difficulty breathing
- Tight chest or chest pain
Blood clots
People with breast cancer have a higher risk of blood clots such as a deep vein thrombosis (DVT).
If you have a DVT, there’s a risk part of the blood clot could break away and travel to the lung. This is known as a pulmonary embolism (PE).
Blood clots can be life-threatening and should be treated quickly.
Blood clot symptoms
Contact your treatment team or go to your local A&E department straight away if you have any of the following symptoms:
- Pain in your arm or leg
- Redness/discolouration of the skin of the arm or leg
- Heat and swelling of the arm or leg
- Swelling, redness or tenderness where a central line is inserted to give chemotherapy, for example in the arm, chest area or up into the neck
- Shortness of breath that comes on suddenly
- Pain or tightness in the chest
- Unexplained cough or coughing up blood
Some symptoms may look different on different skin tones.
Find out more about blood clots.
Sex, contraception and pregnancy
You can still have sex during treatment with chemotherapy or Phesgo. It’s thought chemotherapy drugs cannot pass into vaginal fluids or semen, but this cannot be completely ruled out.
Most treatment teams will advise using barrier methods of contraception, such as condoms, during treatment with chemotherapy or Phesgo.
You’re advised not to become pregnant while having chemotherapy or Phesgo, or for 7 months after your last dose. This is because chemotherapy and Phesgo can harm a developing baby.
If you have not been through the menopause, talk to your treatment team about the most suitable method of contraception for you. It’s still possible to become pregnant even if your periods are irregular or have stopped.
Fertility
If you were diagnosed with breast cancer before you started or completed a family, you may be concerned about your fertility. Depending on your diagnosis and treatment, you may be advised not to get pregnant.
You can talk to your treatment team about any possible fertility preservation options before starting treatment.
Breastfeeding
You’ll be advised not to breastfeed while having Phesgo, or within 7 months of your last dose. This is because there is a risk the drugs could be passed on through breast milk.
Travel and vaccinations
If you’re planning a holiday or need to travel overseas, check with your treatment team first.
You should not have any live vaccines while you’re having treatment.
For more information about vaccines, including COVID-19 and flu vaccines, see our information about vaccines and breast cancer.
7. Further support
Being diagnosed with breast cancer can make you feel lonely and isolated.
Many people find it helps to talk to someone who has been through the same experience as them. You can ask questions and chat to other people on our online forum.
For further information and support or to talk things through, you can call our free helpline. See below for ways to get in touch.
