Trastuzumab (Herceptin®) is a drug used to treat a type of breast cancer called ‘HER2-positive breast cancer’. 

What does treatment with trastuzumab involve?

Trastuzumab is given by slow intravenous (I.V.) infusion. A healthcare professional gives the infusion once a week or once every 3 weeks. The dose depends on the woman’s weight.

The first dose of trastuzumab is higher. This is called a ‘loading dose’. It will usually take about 90 minutes and can be slowed or stopped if the woman feels uncomfortable. If the woman doesn’t react to the first infusion, the other infusions will be quicker and the dose will be lower.

  • For women with HER2-positive early breast cancer, the current recommendation is to give trastuzumab at the same time as chemotherapy (usually after breast cancer surgery). Trastuzumab can only be given with some types of chemotherapy. This means that trastuzumab treatment may not start right at the beginning of chemotherapy. The current recommendation is to give trastuzumab for 1 year.
  • For women with HER2-positive metastatic breast cancer, trastuzumab may be given on its own or with other treatments. Treatment with trastuzumab will usually continue as long as the woman is benefiting from treatment, and as long as the benefits outweigh the risks and side effects.

Trastuzumab can be given at the same time as radiotherapy. However, we don’t yet know the long-term effects of giving trastuzumab at the same time as radiotherapy.

Side effects of trastuzumab

The most significant side effect of trastuzumab is the risk of heart problems.

This risk is increased if trastuzumab is given with anthracycline chemotherapy drugs. Therefore trastuzumab should not be given at the same time as anthracycline chemotherapy (epirubicin (Pharmorubicin®), doxorubicin (Adriamycin®)).

Trastuzumab is generally not recommended for patients with pre-existing heart problems. For women with no pre-existing problemns, the heart will be checked before and during treatment. If heart problems develop while on trastuzumab, heart checks will be more frequent and the woman may be referred to a cardiologist.

Symptoms of heart problems include feeling faint because of low blood pressure, breathing difficulties, tightness in the chest, chest pains, shortness of breath or an irregular heartbeat.

Other possible side effects of trastuzumab include reactions such as chills and fever. Clinical trials looking at the side effects of trastuzumab in women with early breast cancer have not been running for long. Therefore, we do not yet know the long-term side effects of trastuzumab.