Courtesy of Macmillan Cancer Support.

This information is about trastuzumab, which is commonly known as Herceptin®. 

On this page

  • What is Herceptin?
  • How it works
  • When it is used
  • How it is given
  • Possible side effects
  • References

What is Herceptin?

Herceptin is one of a group of cancer drugs called monoclonal antibodies.

Monoclonal antibodies recognise and lock onto specific proteins on the surface of cancer cells. This helps the body's immune system to recognise the cancer cells and destroy them. Monoclonal antibodies are sometimes called targeted therapies because they are designed to target cancer cells.

How it works

Herceptin works by interfering with one of the ways in which some cancer cells divide and grow.

Many types of cells in the body have proteins called growth factor receptors on their surface. When growth factors, which occur naturally in the body, lock onto these receptors the cells are stimulated to grow.

Some cancers have too much of a protein called human epidermal growth factor receptor 2 (HER2) on their surface. They are called HER2 positive cancers. The extra HER2 receptors on HER2 positive cancers helps them to grow.

Herceptin is designed to treat people with some types of HER2 positive cancers. It works by attaching to the HER2 protein on the cancer cells so that growth factor cannot reach the cancer cells. This stops the cells from dividing and growing. Herceptin also works by attracting the body’s own immune cells to help destroy the cancer cells.

Herceptin only works in people who have cancer with high levels of the HER2 protein.

Several tests are available to measure HER2 levels. Testing can be done at the same time as initial cancer surgery, or samples of cancer cells from previous biopsies or surgery may be used.

When it is used

Breast cancer It may be used in the early stages to increase the chances of a cure or in advanced stages to help control the disease if the breast cancer has come back.

Stomach cancer Herceptin may be used in combination with chemotherapy to treat stomach cancer that has spread beyond the stomach (metastatic or advanced gastric cancer).

How it is given

Herceptin is given by a drip into a vein (intravenous infusion). It can usually be given in the outpatient department at the hospital.

The first dose is given slowly, usually over about an hour and a half. After the first infusion you will need to stay in the hospital for about 4–6 hours so that the nurses can monitor you for any reaction to the Herceptin. If you have no problems with this, later infusions will normally take about 30 minutes and you will be able go home soon after they finish.

Herceptin may be given once a week or once every three weeks. If it is given together with chemotherapy drugs, they are given in the normal way, which is usually every three weeks.

Possible side effects

Each person's reaction to a cancer drug is different. Some people have very few side effects, while others may experience more.

We have outlined the most common side effects but haven't included those that are rare and therefore extremely unlikely to affect you. If you notice any effects that aren't listed below, discuss them with your doctor or nurse.

Side effects of Herceptin fall into two groups:

  • Early, infusion-related side effects, which may occur during the infusion or within about 4 hours of the drug being given. These side effects are usually most noticeable with the first dose and less noticeable with following doses.
  • Later side effects, which may occur a few days or weeks after treatment.

Early, infusion-related side effects

Flu-like symptoms may include a headache, high temperature (fever) and chills, feeling sick or being sick. These symptoms can be controlled or reduced with medicines, which your doctor can prescribe for you. They generally get better within a few hours of the infusion finishing.

Allergic reaction? - This is uncommon. Signs may include a skin rash, itching, wheezing, difficulty breathing, and breathlessness. You will be closely monitored during your treatment, but let your nurse or doctor know if you have any of these symptoms. Antihistamines can be given before the infusion to reduce the chance of an allergic reaction occurring.  

Other possible side effects

  • Diarrhoea - This can usually be controlled with medicine, but let your doctor know if it is severe or if it continues. It is important to drink plenty of fluids if you have diarrhoea.
  • Headaches -  Let your doctor know if you have headaches while having treatment with Herceptin.
  • Nausea - This can be troublesome for a day or two after the infusion. Anti-sickness medicines will usually ease the problem of nausea.
  • Effects on the heart - Herceptin may lead to some people having heart problems. It is recommended that Herceptin is not given to people with a history of heart disease or high blood pressure. In order to check your normal heart function, you will have tests (usually an echocardiogram) before starting treatment with Herceptin

If Herceptin is given in combination with chemotherapy, you will also experience the side effects of the chemotherapy drug.

Always let your doctor or nurse know about any side effects you have. There are usually ways in which they can be controlled or improved.


This section has been compiled using information from a number of reliable sources including:

  • British National Formulary. 60th edition. 2010. British Medical Association and Royal Pharmaceutical Society of Great Britain.
  • European Medicines Agency. Summary of product characteristics. (accessed 24 September 2010).
  • CG80 Breast cancer (early & locally advanced): diagnosis and treatment. 2009. National Institute for Health and Clinical Excellence (NICE).
  • CG81 Advanced breast cancer: diagnosis and treatment. 2009. National Institute for Health and Clinical Excellence (NICE).