Targeted therapy for breast cancer

Targeted therapy drugs attack specific features of cancer cells to stop the cancer growing and spreading. Different types of targeted therapy drugs are used for different types of breast cancer.

HER2-targeted agents

For early or locally advanced HER2+ breast cancer, the most common targeted therapy drug used is trastuzumab. Your treatment team may refer to trastuzumab by a brand name (e.g. Herzuma, Kanjinti or Ogivri). It is also known as Herceptin, although this version is now rarely used in Australia.

Trastuzumab works by attaching itself to HER2+ breast cancer cells, destroying the cells or reducing their ability to divide and grow. It also encourages the body’s own immune cells to help find and destroy cancer cells. Usually used in combination with chemotherapy drugs for early breast cancer, trastuzumab can increase the effect of the chemotherapy.

Trastuzumab can be given through a drip into a vein (infusion) or as an injection under the skin. The first infusion takes about 90 minutes (called the loading dose). The following infusions each take 30–60 minutes.

You will usually have a dose every 3 weeks, for up to 12 months. The first 4–6 doses are given while you are having chemotherapy treatment.

Side effects

Side effects are usually caused by the chemotherapy drugs, and often ease once chemotherapy finishes and you are having trastuzumab only. Side effects from trastuzumab are uncommon, but can include headache, fever and diarrhoea. In some cases, trastuzumab can affect how the heart works, so you will have tests to check your heart function before and during treatment.

CDK inhibitors

Abemaciclib is a type of cyclin-dependent kinase (CDK) inhibitor. It is used with hormone therapy. Abemaciclib may be used after surgery and chemotherapy for larger, high-risk ER+, HER2– breast cancers, for cancers involving several lymph nodes, or cancers at high risk of returning. Another drug (ribociclib) may soon become more widely available.

Side effects

Nausea or diarrhoea may occur, but this can be managed. Your blood count may be affected, so regular blood tests are needed.

PARP inhibitors

There are several new drugs for people who have inherited a BRCA mutation, or whose cancer has developed BRCA mutations. These are called poly (ADP-ribose) polymerase (PARP) inhibitors and include the drug olaparib. Ask your doctor if this may be suitable for you.