Trastuzumab (Herceptin)

Trastuzumab is a monoclonal antibody – a type of targeted treatment for breast cancer. It is also licensed for use with capecitabine or fluorouracil and cisplatin chemotherapy for a type of stomach cancer called adenocarcinoma of the stomach or cancer where the food pipe meets the stomach. The stomach cancer must be HER2 positive, have spread to another part of the body and not already been treated.

Trastuzumab can control the growth of cancer cells that produce too much of a protein called HER2. Between 20 and 25 out of every 100 women (20 to 25%) diagnosed with early breast cancer have a cancer that produces too much of the HER2 protein. Doctors call this HER2 positive cancer. Trastuzumab only works for people whose cancer is HER2 positive. Up to 30% of women with breast cancer that has spread have HER2 positive cancer. There is more about treatment for breast cancer in the breast cancer section of CancerHelp UK.

You have trastuzumab into your bloodstream by injection through a fine tube (cannula) into a vein (intravenously). Or you may have it through a central line that goes into a vein near your collarbone. For advanced breast cancer, you usually have the infusion once a week or 3 weekly. For early breast cancer, you have it every 3 weeks. Treatment takes about 30 to 90 minutes each time.

The side effects associated with trastuzumab are listed below. You can use the links (underlined) to find out more about each side effect or look in the cancer drug side effects section.

More than 10 in every 100 people have one or more of these.

• Fatigue during and after treatment – most people find their energy levels are back to normal from 6 months to a year after their treatment finishes.
• A reaction to the drug causing chills, fever and possibly an itchy rash, feeling sick, breathlessness, wheezing, a headache, flushes and faintness – this happens to about half of patients with the first treatment but usually wears off with further treatments. More rarely, it is possible to have a more severe reaction to your first infusion, but your nurse will be watching for this
• Diarrhoea – this affects about 1 in 3 people. It is usually mild but do tell your doctor or nurse as you can be given medicines to stop it
• Heart problems – this only happens in a few people and should get better once treatment is stopped. Your heart function will be tested before you start treatment and monitored regularly throughout your treatment. You cannot have this drug for early breast cancer if you already have particular heart conditions such as congestive heart failure or angina that needs treatment
• Pain – this may affect the abdomen, chest, joints or muscles
• It is not yet known whether trastuzumab can have a harmful effect on a developing baby – you should talk about contraception with your doctor before having the treatment if there is any chance you or your partner could become pregnant

Fewer than 1 in 100 people have these.

• A drop in white blood cell count causing increased risk of bacterial infection – if you have an infection, you may have headaches, aching muscles, a cough, sore throat, and pain when passing urine or feel cold and shivery. Infections can sometimes be life threatening. You should urgently contact your treatment centre if you think you have an infection
• Difficulty breathing and a cough
• Liver problems – you may have regular blood tests to check this
• Difficulty sleeping
• Loss of fertility – it is not known exactly what effect this drug may have on your fertility. It is important to talk with your doctor before starting treatment if having a baby is important to you
• Women may stop having periods (amenorrhoea) – this may only be temporary

The side effects above may be mild or more severe. A side effect may get better or worse through your course of treatment, or more side effects may develop as the course goes on. This depends on

• How many times you've had the drug before
• Your general health
• The amount of the drug you have (the dose)
• Other drugs you are having

Talk to your doctor, pharmacist or nurse about all your side effects so that they can help you manage them. Your specialist nurse, clinic or ward nurse should give you a contact number. You can ring if you have any questions or problems. They can give you advice or reassure you. If in doubt, call them.

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and other over the counter remedies – some drugs can react together.