Herceptin is the brand name of a medicine called trastuzumab.

It's used to treat some types of breast cancer and stomach cancer (see below).


HER2 (human epidermal growth factor receptor 2) is a type of protein. HER2 is present in all human cells, but in certain types of cancer the levels are unusually high.

High levels of HER2 are found in some types of breast and stomach cancer. These are known as HER2 positive cancers. About one in five cases of breast cancer and stomach cancer are HER2 positive.

Herceptin can be used to help control the growth of cancerous cells that contain high amounts of HER2. It works by blocking the effects of the protein and encourages the immune system (the body’s natural defence system) to attack the abnormal cells.

When Herceptin is used

Herceptin can be used to treat:

  • early HER2 positive breast cancer, following surgery and/or radiotherapy and chemotherapy to reduce the risk of the cancer re-occurring
  • advanced HER2 positive breast cancer that has spread from the breast (metastatic breast cancer) – it can be given on its own or in combination with chemotherapy
  • advanced HER2 positive stomach cancer that has spread out of the stomach (metastatic stomach cancer)
  • advanced HER2 gastro-oesophageal cancer; where the oesophagus (food pipe) meets the stomach

Herceptin can't cure metastatic breast and stomach cancers, but it can slow their growth and increase survival time.

How Herceptin is given

Herceptin is given by infusion (where the medication is fed slowly into your bloodstream through a drip), or by subcutaneous injection (an injection with a fine needle under the skin).

The treatment will be carried out at a hospital or clinic, and a session usually lasts about an hour. The number of sessions you need will depend on the type of cancer and how advanced it is. The first session will be longer because you'll be monitored for any unusual reactions to herceptin.

If you're being treated for breast cancer, you'll need treatment every one to three weeks. Stomach cancer is usually treated with a session once every three weeks.

Early-stage breast cancer will require treatment for a year. In cases of breast or stomach cancer that has spread, treatment will be needed for as long as it's controlling the cancer.


Herceptin isn't usually recommended for people with pre-existing heart problems or poorly controlled high blood pressure (hypertension). This is because it can cause heart problems.

If you need to take herceptin, your heart will be regularly tested to make sure there are no problems.

Herceptin isn't usually recommended during pregnancy because it can harm the developing baby.

You should avoid becoming pregnant if you're taking herceptin and for seven months after taking it. Your GP will be able to advise you about contraception.

Side effects of Herceptin

Side effects are most frequently experienced immediately after treatment with Herceptin. They usually last a few hours and tend to become milder and less frequent the more treatments you have.

Commonly reported side effects that affect more than one in 10 people include:

  • an inital reaction to the medication – it can cause chills, a high temperature, swelling of the face and lips, headache, hot flushes, feeling sick, wheezing and breathlessness
  • soreness at the injection site
  • tiredness – in most cases, energy levels are back to normal six to 12 months after treatment has finished
  • an itchy red rash can develop on the skin
  • diarrhoea – this tends to affect about one in three people and is usually mild
  • heart problems – such as palpitations or an irregular heartbeat; these symptoms should improve after treatment finishes
  • pain in your muscles, joints, chest or abdomen
  • high blood pressure (hypertension) or low blood pressure (hypotension)
  • sore, red eyes (conjunctivitis)
  • watery eyes
  • runny nose
  • shaking (tremor)
  • hot flushes
  • dizziness

You can read more about the possible side effects of Herceptin, including the less common side effects, on Cancer Research UK.

Tell the doctor in charge of your care if you experience particularly troublesome side effects after taking Herceptin. Medicines are available to treat some of the side effects.

Read more about Herceptin in the Medicine A-Z.

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