All cancers begin when changes occur in our genes. A change in a gene that disrupts its function is called a ‘mutation’ or a ‘pathogenic variant’. Cancer usually results from an accumulation of many mutations. Most of the time, those mutations are confined (at least initially) to the cells of the organ or tissue where they started. We call these type of genetic mutations ‘somatic’. Somatic mutations are not inherited from our parents, and they are not passed down to our children. This is why the majority of cancers do not ‘run in families’.

Cancer can get a ‘head start’ if the first mutation is inherited from a parent rather than somatic. In this case the mutation is present in every cell of a person’s body. People who inherit mutations in particular genes are at higher risk of developing particular cancers.

Breast cancer is one of the most common cancers affecting women, affecting approximately 11.7% of Australian women³. Inherited mutations in the BRCA1 and BRCA2 genes are rare – found in only around 1/225 – 1/500 (0.2% – 0.4%) of people⁴, and mutations in many of the other breast cancer genes are even rarer. The majority of people who are diagnosed with breast cancer will not have an inherited gene mutation predisposing to breast cancer.

A person who has inherited a mutation in a breast cancer predisposing gene will often (but not always) have some of the following features in themselves or in their family history:

• Individuals who have been diagnosed with breast cancer at a young age (under 50-years-old)
• More than two relatives on the same side of the family who have also been diagnosed with breast cancer
• Relatives who have had ovarian cancer, prostate cancer or pancreatic cancer, especially if they were young at the time of diagnosis
• Males relatives who have had breast cancer
• Ashkenazi Jewish ancestry (Jewish ancestors who came from central or Eastern Europe)

Sometimes, even in the absence of any of these features, a woman whose breast cancer has specific features (such as ‘grade 3 triple negative’ breast cancer, which has no receptors for oestrogen, progesterone and does not over-express the HER2 protein) may be at increased risk of having a hereditary predisposition to breast cancer.

If you have been diagnosed with breast cancer, ask your doctor whether they feel that genetic testing would be indicated for you. It will be helpful if you can collect information about your family history of cancer prior to having this discussion. Your doctor may organise genetic testing for you directly, or they may refer you to a genetic counsellor/genetics clinic or familial cancer service to have this done.

Ovarian cancer is less common than breast cancer, affecting just under 1% of Australian women³. There are several different types of ovarian cancer and some of them (such as cancers arising from egg cells) are rarely hereditary. But for other types of ovarian cancer, more than 10% can be caused by hereditary gene mutations.

A person who has inherited a mutation in an ovarian cancer predisposing gene will often (but not always) have some of the following features in themselves or in their family history:

• Individuals who have been diagnosed with ovarian cancer at a young age (under 50-years-old)
• More than two relatives on the same side of the family who have also suffered from breast or ovarian cancer, especially if any were diagnosed under 50 years of age
• Relatives who have had prostate cancer or pancreatic cancer
• Males relatives who have had breast cancer
• Ashkenazi Jewish ancestry (Jewish ancestors who came from central or Eastern Europe)
• A personal or family history of bowel or uterine cancer

Sometimes, even in the absence of any of these features, a woman whose cancer has specific features (a high grade serous ovarian cancer, or a cancer arising in the fallopian tube or the peritoneum) may be at increased risk of having a hereditary predisposition to ovarian cancer.

Sometimes genetic testing is performed on the DNA from ovarian tumours by oncologists, to help determine which drugs would work best to treat the tumour. If this genetic testing finds a mutation in an ovarian cancer predisposing gene, such as BRCA1 or BRCA2, follow up genetic testing on DNA from a blood sample is recommended to find out if the mutation that was found in the tumour is somatic (i.e. has arisen in and is confined to the tumour) or if it is inherited.

Sometimes a special protein-staining test is performed on ovarian tumours. If this special test reveals that certain proteins called ‘mis-match repair’ proteins are missing in the tumour, follow up genetic testing on DNA from a blood sample is recommended to find out if the person might have Lynch syndrome (an inherited predisposition to bowel, uterine and ovarian cancer).

If you have been diagnosed with ovarian cancer, ask your doctor whether they feel that genetic testing would be indicated for you. It will be helpful if you can collect information about your family history of cancer prior to having this discussion.

Genetic testing can be done using DNA extracted from white blood cells (a blood test) or from cells present in saliva. Unlike regular blood tests, it usually takes around four to six weeks to get a result.

In Australia, genetic testing for hereditary breast cancer and ovarian cancer is funded by Medicare, but only when certain criteria about the tumour and family history are met. The test can only be requested by a specialist (for example, a geneticist, surgeon or oncologist) or by a genetic counsellor. This type of testing cannot be accessed through your GP. Your specialist or genetic counsellor can assess whether or not you meet the criteria for Medicare funded testing. If you do not meet the Medicare criteria, you can still have genetic testing, but you will need to cover the cost of this. Genetic testing usually costs approximately $350 – $500 depending on the number of genes tested and the laboratory performing the testing.