Metastatic Breast Cancer

Metastatic breast cancer, also called advanced breast cancer or secondary breast cancer, is where cancer cells have spread from the breast to more distant parts of the body. The most common metastatic sites in breast cancer include the bones, liver, lungs, lymph nodes and brain.

How is metastatic breast cancer different from early breast cancer?

Metastatic breast cancer is where cancer cells have spread from the original site of disease in the breast to more distant parts of the body. Usually, metastatic breast cancer occurs after previous treatment for early breast cancer. In around 10-15% of people diagnosed with metastatic breast cancer, there is no prior history of early breast cancer. This is called ‘de novo’ metastatic breast cancer.

Metastatic breast cancer is unfortunately an incurable disease. Prognosis depends on many factors, especially the specific subtype of breast cancer. Advances in treatment mean that some people live with metastatic breast cancer for many years. These factors will be discussed with you at your consultation.

What are the treatment options for metastatic breast cancer?

The aim of treatment in metastatic breast cancer is to prolong survival and maintain quality of life for as long as possible There are many treatment options available, and new ones in development. The suitability of treatment options will vary greatly depending on the specific subtype of cancer:

Hormone receptor positive, HER-2 negative metastatic breast cancer

This type of metastatic breast cancer is usually managed initially with hormonal (endocrine) therapy. The specific treatment recommended will depend on your previous treatment and individual circumstances. Options may include aromatase inhibitors, tamoxifen, fulvestrant, or a relatively new type of medication called a CDK inhibitor which can be given in combination with aromatase inhibitors or fulvestrant. There are three different CDK inhibitors (palbociclib, ribociclib and abemaciclib) each with a slightly different side effect profile.

Chemotherapy is also used, although usually this is reserved for when endocrine therapy has stopped being effective. The specific order of chemotherapy treatments will depend on consideration of previous treatment and balancing potential side effects and effectiveness.

HER-2 positive metastatic breast cancer

For most people, initial treatment will involve a taxane-based chemotherapy (paclitaxel or docetaxel) in combination with targeted therapies called trastuzumab (Herceptin) and pertuzumab (Perjeta). Usually the chemotherapy component will be given for up to six months in combination with trastuzumab and pertuzumab , after which the trastuzumab and pertuzumab will be continued as maintenance therapy.

If these treatments stop being effective, or are not appropriate as initial treatment, a treatment called TDM1 (aka trastuzumab emtansine or Kadcyla) is used. This is a unique type of medicine called a drug-antibody conjugate, which in this case is a chemotherapy molecule attached to a targeted therapy that binds to the HER2 receptor.

If TDM1 stops being effective, further treatment options include trastuzumab or lapatinib (Tykerb) combined with an oral chemotherapy called capecitabine, or trastuzumab combined with a range of other chemotherapies. New treatments including tucatinib and trastuzumab-deruxtecan (Enhertu) will also hopefully be available in Australia in the near future which will expand treatment options for HER2 positive metastatic breast cancer.

For HER2 positive metastatic breast cancer which is also hormone receptor positive, treatment may include endocrine therapy (hormone therapy) such as an aromatase inhibitor or tamoxifen (in addition to the treatment outlined above).

Triple negative metastatic breast cancer

For most people, initial treatment will involve chemotherapy. The combination of chemotherapy treatments will depend on previous treatment and balancing potential side effects with the effectiveness of individual options.

Sacituzumab govitecan is an example of a relatively new class of drug called an antibody-drug conjugate (ADC). These are a type of targeted cancer therapy that combine the specificity of antibodies with the cytotoxicity of chemotherapy drugs. This allows for targeted delivery of the chemotherapy drug to cancer cells, while minimizing damage to healthy cells. Sacituzumab govitecan is an ADC that targets the TROP-2 protein, which is overexpressed in breast cancer. It has been shown to be helpful in patients with triple negative breast cancer who have already received one line of treatment in the metastatic setting, and is now available on the PBS.

Where triple negative cancers express a molecule called the PDL1 receptor on the cells, a type of treatment called immunotherapy may be recommended (e.g. pembrolizumab). This is given in combination with chemotherapy such as paclitaxel, nab-paclitaxel or carboplatin and gemcitabine. Pembrolizumab is not PBS-funded in Australia although currently there is a compassionate access program which provides the drug free of charge to eligible patients. Ask your treating doctor for more information about this program.

For people with germline mutations in BRCA1 or BRCA2 (inherited genes which predispose to the development of breast or ovarian cancer), a targeted therapy called olaparib (a PARP inhibitor) may be considered.

Because triple negative metastatic breast cancer can commonly become resistant to chemotherapy, new strategies targeting specific pathways in cancer cells are being studied, using medicines such as tyrosine kinase inhibitors, immunotherapy or novel agents. Clinical trials may be considered, which may enable access to some of these new or promising treatments not yet otherwise available in Australia.

Supportive and palliative care and metastatic breast cancer

Managing symptoms and any side effects of treatment is very important for people living with metastatic breast cancer. Sometimes, specific expertise is required to manage complex or difficult symptoms. As a dual-trained medical oncologist and supportive and palliative care physician, Dr Forster is a specialist in this area.

Dr Forster can help you maintain independence and enhance quality of life by providing specialist advice on how to manage the symptoms of metastatic breast cancer. Dr Forster works with specialist McGrath Breast Care nurses, and a Palliative Care nurse consultant, who are able to provide additional advice and support. Our team can also refer to the local community palliative care service in your area to provide support at home and access to allied health professionals as required.