What is breast cancer?

There are many different types of breast cancer and each type is treated in a different way. 

The doctor may talk about the ‘receptor status’ of breast cancer. This describes whether a tumour can recognize signals that tell the tumour cells to grow. The most common types of receptor status are:1,2

• Estrogen-receptor positive or ER+

• Progesterone-receptor positive or PR+

• HER2-positive or HER2+

The receptor status of a tumour is found from a sample of cancer cells taken from the tumour (this is called a ‘biopsy’). Importantly, knowing the receptor status means that the healthcare team can better understand the type of breast cancer the person has and select the best treatment to give each patient the best chance of fighting the cancer.3

Approximately 80 out of 100 breast cancers are ER+ and 65 out of 100 are PR+. This means that the cancer cells in the biopsy have receptors for the hormones estrogen and progesterone.4 

A receptor status of HER2+ means that HER2 receptors are ‘overexpressed’ on the surface of the breast cancer cells. This means there are an unusually large number of receptors present.2

HER2 receptors tell cells to grow, so too many of these receptors may cause a cell to grow too quickly and a tumor starts to grow.2

A diagnosis of triple-negative breast cancer means that the three most common types of receptors known to promote the growth of breast cancer (estrogen, progesterone and HER2) are not present in the tumor.5,6 Triple-negative breast cancer occurs in about 10–20 out of every 100 diagnosed breast cancer cases and can sometimes be more aggressive and harder to treat.7

Key: Breast cancer cells (large blue circles) can have different receptors (small blue squares, blue triangles or small blue circles) on the surface that receive signals to tell the cells to grow (purple). If the breast cancer is triple negative, none of the common receptors are present, making the cancer harder to treat. 

It is not fully understood what leads to the development of breast cancer, but there are some things that can increase a person’s chances of getting the disease, called ‘risk factors’. Some risk factors are:8

• Family history – breast cancer risk is about double in women with one close relative (parent, sibling or child) with breast cancer, however more than 8 in 10 women with a close relative with breast cancer will never develop breast cancer themselves.

• ‘BRCA’ gene – women who have an error in the BRCA gene have around a 1 in 2 chance of developing breast cancer.

• High levels of ‘sex hormones’ – having high levels of hormones like estrogen and progesterone doubles the risk of breast cancer after menopause.

• Having taken oral contraceptives or hormone replacement therapy – they contain synthetic sex hormones.

• Being overweight.

• Drinking alcohol.

Some of the signs and symptoms of breast cancer include:9

• A lump in the breast.

• A change in the size or shape of the breast.

• Dimpling of the skin or thickening in the breast tissue.

• A nipple that has turned in (inverted).

• A rash (like eczema) on the nipple.

• Discharge from the nipple.

• Swelling or a lump in the armpit.

• Pain or discomfort in the breast that does not go away.

A lump in the breast is the most common symptom of breast cancer. Most breast lumps are not cancer, but it is important to get anything that is unusual for you checked by your doctor.

If the cancer cells have estrogen or progesterone hormone receptors, the doctor may suggest ‘hormone therapy’ drugs. This type of drug helps to slow or stop the growth of cancer cells with hormone receptors by cutting off or lowering the levels of estrogen and progesterone hormones in the body.1,4

Hormone therapies (sometimes known as ‘endocrine therapies’) may offer the best treatment for breast cancers that are ER+ or PR+. However, if a tumour does not test positive for these receptors, hormone therapy is unlikely to work.4 In addition, some cancers may become resistant to hormone therapy over time, which means that these treatments may stop working.10

There are medicines that specifically target HER2+ cancers. ‘Targeted drugs’ are treatments that can attack breast cancer cells without harming normal cells. One type of targeted therapy currently being studied is called ‘monoclonal antibody therapy’. These therapies block the HER2 receptors and stop the cancer from growing.11

Targeted drugs sometimes work even when chemotherapy drugs do not. Some targeted drugs can help other types of treatment work better.12

Scientists and doctors are working to find new treatment options for people diagnosed with TNBC. Since the tumour cells do not have any of the most common receptors, common treatments like hormone therapy and HER2-targeting drugs will not work with TNBC.7 Current research aims to find other new ways of stopping cancer cell growth. 

Using chemotherapy to treat TNBC is still a good option. In fact, TNBC may respond even better to chemotherapy in the earlier stages than many other forms of cancer.7 A mix of treatments is often used for TNBC, including chemotherapy, radiotherapy and surgery.

For people diagnosed with TNBC, and for people whose treatment for ER+ or PR+ breast cancer has stopped working, clinical trials may give extra options on top of standard treatment. These may include ‘cancer immunotherapy’. 

Cancer immunotherapy helps the body’s own immune system to fight cancer. While immune cells are able to find and kill abnormal cells, cancer cells often find ways to protect themselves from immune attack. Cancer immunotherapy aims to beat these protections so that immune cells can still find and destroy cancer cells.13

The doctor should be able to advise on other available treatment options.

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References