A HER2-targeted antibody
Trastuzumab
A targeted antibody for HER2-positive breast and stomach cancers, given by drip or injection by oncology teams.
What is Trastuzumab?
Trastuzumab is a targeted cancer medicine (a monoclonal antibody) used for cancers that make too much of a protein called HER2, most often HER2-positive breast cancer and some stomach cancers. It is given by a specialist oncology team as a drip into a vein or an injection under the skin, usually together with chemotherapy. Because it can affect how well the heart pumps, your team checks your heart with scans before and during treatment. Reactions during the infusion can happen, so you are watched closely and given supportive medicines.
Education and reference only. This is a plain-language guide to Trastuzumab — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Trastuzumab is a monoclonal antibody, a laboratory-made protein designed to lock onto HER2, a growth protein found in large amounts on some cancer cells. It is used mainly for HER2-positive breast cancer and certain HER2-positive stomach cancers, where it can help chemotherapy work better and lower the chance of the cancer coming back. It is not a tablet; it is given by oncology specialists as a drip into a vein or, for some forms, an injection under the skin. Brands include Herceptin and the biosimilars Herzuma, Kanjinti and Ontruzant.
How it works
HER2 is a protein on the surface of cells that tells them to grow and divide; some cancers carry far too much of it and grow quickly as a result. Trastuzumab attaches to HER2 on the cancer cells, blocking the growth signal and flagging the cells so the immune system can help destroy them. It is usually combined with chemotherapy, which works in a different way, so the two together are more effective than either alone. Because HER2 also has a small role in heart muscle, the medicine can sometimes affect how strongly the heart pumps, which is why heart function is monitored.
Company & origin
Originated / developed by: Various (originator and biosimilars).
A targeted cancer antibody used in the UK by oncology teams to treat HER2-positive breast and stomach cancers, usually alongside chemotherapy.
Practical use
How to take Trastuzumab
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given by your oncology team as a drip into a vein, or for some forms as an injection under the skin; it is never taken as a tablet.
- You may be given supportive medicines, such as paracetamol or an antihistamine, before the drip to lower the chance of a reaction.
- Your team will arrange heart scans before treatment and regularly during it to keep an eye on how your heart is pumping.
- Attend all your scheduled sessions and blood tests, as the course is planned to run over many months.
- Tell your team straight away about breathlessness, swollen ankles, a persistent cough or a fast or irregular heartbeat.
Weighing it up
Advantages & disadvantages of Trastuzumab
Advantages
- Specifically targets HER2-positive cancers and can make chemotherapy more effective.
- Can lower the chance of HER2-positive breast cancer returning after surgery.
- Available as a vein drip or, in some forms, a quicker injection under the skin.
Disadvantages
- Can weaken the heart's pumping action, so regular heart scans are needed and treatment may be paused.
- Infusion reactions such as chills, fever and flushing can happen, especially with the first doses.
- Only works for cancers that are HER2-positive, so it is not suitable for everyone.
Practical use
Good to know
Trastuzumab only helps cancers that are HER2-positive, so your team tests the cancer first to check it carries enough HER2. The most important safety point is its effect on the heart: it can weaken the heart's pumping action, so you will have heart scans (echocardiograms or similar) before starting and at intervals during treatment, and the medicine may be paused if your heart needs time to recover. Reactions during the first infusions are fairly common, such as chills, fever or feeling flushed, so you are watched closely and given supportive medicines beforehand. Tell your team about any breathlessness, swollen ankles, a cough that will not settle or a racing heartbeat, as these can be signs the heart is affected. Treatment is usually given over many months as part of a planned course.
Who should not take it / use with caution
- People with significant existing heart problems may not be able to have it, or will need very careful monitoring.
- It is generally avoided in pregnancy because it can harm the developing baby, so effective contraception is advised.
- Anyone who has had a serious allergic reaction to trastuzumab should not receive it again.
Monitoring
- Heart scans (such as echocardiograms) before treatment and at intervals to check the heart's pumping action.
- Watching closely during infusions for reactions, and giving supportive medicines as needed.
- Regular blood tests and reviews of how the cancer is responding, often with scans.
Side effects
- Infusion reactions such as chills, fever, flushing and feeling unwell, mainly with early doses.
- A reduced heart pumping action, which is why heart scans are done; tell your team about breathlessness or swollen ankles.
- Tiredness, aches, diarrhoea and a higher risk of infections, especially when given with chemotherapy.
Key interactions
- Often combined with chemotherapy and other HER2 medicines such as pertuzumab as a planned treatment, not an accidental interaction.
- Certain chemotherapy drugs that can also affect the heart may add to the strain, so your team plans the combination carefully.
- Tell your team about all your medicines and any heart medicines, so monitoring can be adjusted.
Available as: Given by oncology teams as a drip into a vein, or as an injection under the skin for some forms.
Answers
Trastuzumab: frequently asked questions
Why do I need heart scans during trastuzumab?
Trastuzumab can sometimes weaken the heart's pumping action, so your team checks your heart with scans before and during treatment and pauses the medicine if needed; this usually recovers.
Is trastuzumab a type of chemotherapy?
No. It is a targeted antibody that locks onto the HER2 protein on cancer cells, and it is often given together with chemotherapy, which works in a different way.
What is a HER2-positive cancer?
It is a cancer that makes too much of a growth protein called HER2; your team tests the cancer first, because trastuzumab only helps HER2-positive cancers.
Why might I feel unwell during the first drip?
Infusion reactions such as chills, fever or flushing are fairly common early on; you are watched closely and given supportive medicines to reduce them.
How long will I be on it?
It is usually given over many months as a planned course; your oncology team will explain your schedule and how your progress is monitored.
Authoritative sources
- BNF
- NICE CKS
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