Breast cancer risk in families

Most people who develop breast cancer do not have a close relative with the disease.

In fact, 90 to 95% of breast cancers have nothing to do with family history.

People can’t ‘inherit’ breast cancer itself, but 5 to 10% of people do inherit a genetic mutation that increases their risk.

How genes affect the risk of breast cancer

We all have 2 copies or sets of each gene, one from our mother and one from our father. Each gene helps make proteins in our cells, which help our bodies work properly and stay healthy.

A fault or mutation in one copy of a gene stops it from working properly. This means a history of breast cancer on your father’s side is just as important as on your mother’s side.

What is a strong family history?

If 2 or more people in your close family meet any of the following criteria, the family history is classed as strong:

• diagnosis of breast cancer under the age of 40
• breast cancer that is triple negative
• a number of first-degree relatives with breast or ovarian cancer
• breast and ovarian cancer in the same woman
• many people on the same side of the family affected by breast, ovarian, pancreatic or prostate cancers, sarcoma or melanoma
• male breast cancer
• breast cancer occurring in both breasts (‘bilateral’)
• Ashkenazi Jewish ancestry. 

If you do not have a family history of breast cancer it is unlikely your family is at increased risk.

Which genes increase the breast cancer risk?

The most common inherited mutations that increase the risk of breast cancer are in the genes BRCA1 and BRCA2.

We explain these and even less common gene abnormalities at Genetic mutations and breast cancer risk.

Understand your inherited risk of breast cancer

If you’re worried your family may have a higher risk of developing breast cancer, you can:

• talk to your GP or breast cancer specialist
• use the iPrevent breast cancer risk tool to assess the significance of your family history

Breast cancer and risk in families is complex, both in investigating and interpreting results.

If you or your family may have a higher than usual risk of developing breast cancer, you should be offered genetic counselling. This can help you decide whether to have genetic testing.

Knowing if you carry a gene mutation can help guide your decisions about the best treatment for you.

Testing at family cancer clinics

If you are particularly worried, contact a family cancer clinic. They can help you understand how relevant your family history of cancer is.

Consultations are free to see a familial cancer team in a public hospital. Genetic testing is free for people who meet certain family history criteria. You will have access to counselling before and after testing.

Some people who don’t meet the criteria choose to fund a genetic test themselves. This can cost several hundred dollars. Find out about Genetic testing.

Family cancer clinics can help you create a health plan to manage your risk. This may include:

• changing habits and lifestyle factors
• regularly monitoring your breasts for any changes (with mammography and sometimes special tests like MRI)
• taking medication
• having risk-reducing surgery. 

It’s always your decision about which options you want to explore. Clinicians are very experienced in helping you decide what’s right for you as an individual.

Family cancer clinics operate through public hospitals and some private hospitals. Ask your GP to refer you to a clinic in your area. You can also contact a clinic yourself to make an appointment.