Find out more about the use of biological therapies and whether they may be suitable for you.

How does trastuzumab (Herceptin) work?

Some breast cancers have a lot of a receptor for a molecule called HER2 on the cells’ surface.

Trastuzumab (Herceptin) is a biological therapy made from an antibody that attaches to the HER2 receptor of cells. It is made with an antibody. By doing so, it stops these cells from growing and can also cause them to die.

If your cancer doesn’t have many HER2 receptors, trastuzumab will not treat your cancer because the drug won’t attach to the cancer cells.

Is trastuzumab (Herceptin) right for me?

Whether and when your oncologist recommends trastuzumab for you will depend on:

  • How much HER2 receptor your cancer cells have
  • Which anticancer drugs you’ve already received (if any)
  • Your general health, including your heart and lung function

If trastuzumab is suitable for you, you might be given it as your first therapy, along with chemotherapy. Alternatively, you may receive it after chemotherapy. Your treatment team will explain what timing they think would be most suitable for you.

Are there any serious risks with trastuzumab (Herceptin)?

If you have some heart problems already, your oncologist may recommend you don’t have trastuzumab. This is because trastuzumab can cause congestive heart failure, which can be fatal. Your heart function will be checked before and during your treatment if needed.

Uncommonly, people can experience an allergic reaction during their first trastuzumab drip. This can cause blood pressure changes and difficulty breathing. This usually gets better by stopping the infusion or slowing it down. Most patients can continue their treatment course.

Make sure your oncologist explains the risks of trastuzumab to you, so you’re informed and can balance this up against the possible benefits.

What are the other main side effects of trastuzumab?

Side effects are generally rare with trastuzumab, but you might experience:

  • A reduction in the number of your blood cells, which may cause fatigue and increase your risk of infections
  • Diarrhoea, nausea, or vomiting
  • Loss of appetite and weight loss
  • Difficulty sleeping or feeling weak
  • Hot flushes
  • Joint and muscle pain
  • Skin changes

What help is available for side effects?

You may not get any problems with trastuzumab, but if you do, treatments are available to help.

For example, treatments can reduce diarrhoea. You can find out more about treatments to help with infections, fatigue and pain in our section on quality of life.

Are there any other biological therapies?

A biological therapy called pertuzumab (Perjeta) can sometimes be used alongside trastuzumab and chemotherapy.

Similarly to trastuzumab, pertuzumab targets cells with the HER2 receptor, stopping them from growing and causing them to die. When used together these treatments can lengthen the time before your cancer begins to grow again.

Pertuzumab (Perjeta) is not currently available on the NHS in Scotland, but your oncologist may be able to request a prescription for you. For information, see our section on access to anticancer drugs.

If your cancer begins to grow despite trastuzumab treatment, you might be offered a different treatment.

This might be chemotherapy or a different biological therapy such as trastuzumab emtansine (Kadcyla). Trastuzumab emtansine also targets cells that have a lot of HER2 receptors and causes them to die.

You might also be invited to take part in a clinical trial.

Tips and advice

Advice on getting the best care

To help you feel confident you’re getting the best care, you may want to:

  • Ask your oncologist to explain what your treatment options are, and why they are recommending a particular drug for you
  • Ask whether there are any additional options for you, including new drugs, clinical trials or treatment at other centres
  • Go over the risks and benefits of each treatment with your oncologist
  • Speak up if your treatment is giving you side effects – your treatment team can often help

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Breast Cancer Now’s health information is produced following best practice guidelines developed by the Patient Information Forum. 

Find out more about how we develop our health information and the Patient Information Forum.