Want to know more about breast cancer and genetics? This Q&A will have all the answers

Posted on 20 September, 2022

October is Breast Cancer Awareness Month, and with breast cancer still being the most diagnosed cancer in women, we wouldn’t blame you if you had a few questions.

So to answer everything you’ve ever wondered about genetic breast cancer, Breast Cancer Trials (Australia’s largest oncology research group) is hosting an expert Q&A.

Hosted by Australian political journalist, commentator, and television host Annabel Crabb, some of the country’s top genetic breast cancer experts along with breast cancer survivor Karen Alexander will talk about genetics, how it relates to breast cancer as well as current research.

Ahead of the Q&A, HerCanberra sat down with Breast Cancer Trials to ask a few questions.

Can you tell me what percentage of breast cancers are caused by genetics?

Approximately 5-10% of breast cancer cases are thought to be hereditary, where the gene mutation has been passed on directly from a parent.

The most commonly inherited gene mutations are known as the BRCA1 or BRCA2 gene mutations. In normal cells, these genes help make proteins that repair damaged DNA. Mutated versions of these genes result in the accumulation of damaged DNA which can lead to abnormal cell growth, which can then lead to cancer.

If someone has a ‘breast cancer causing’ genetic mutation, what is the likelihood that they would pass this onto their children? And their grandchildren?

Both women and men who have inherited an abnormal breast cancer gene have a 50% risk (or one-in-two chance) of passing the abnormal gene on to their child.

What percentage of the population has the BRCA gene mutation?

It is estimated that in Australia today, about one in 400 women are at the highest risk of breast cancer because they carry a BRCA1 or BRCA2 gene mutation. For these people, carrying a BRCA1 gene mutation is associated with an approximate 72% risk of developing breast cancer over the course of their lifetime. And they can have a risk of up to 44% of developing ovarian cancer. BRCA2 is associated with around a 69% chance of breast cancer and 17% chance of ovarian cancer of a lifetime.

Jewish women of eastern European ancestry (Ashkenazi) are more likely to carry a BRCA1 or BRCA2 gene mutation, estimated to be present in about one in 40 women. This is 20 times more common than in the general population.

When should I consider getting genetic testing? Should everyone get it?

Genetic testing is often offered to women who are diagnosed with breast cancer at an early age (35 and under), who have a strong family history or who are diagnosed with certain types of breast cancer such as ‘triple negative breast cancer’. If a gene mutation such as in BRCA1 or BRCA2 (the most common types) is identified, this can be associated with a family history of breast, ovarian, prostate and some other types of cancer. It is important to note that family history can come from your mother’s or father’s side of the family.

How do I go about getting genetic testing done? Where do I start?

Genetic testing is offered only through a Familial Cancer Clinic or appropriately qualified professionals such as an oncologist. If a woman is referred to a Familial Cancer Clinic, the availability, limitations, potential benefits, and possible consequences of genetic testing will be discussed with her. If you are concerned about your strong family history of breast cancer, or you have a close family member with a BRCA gene mutation, speak with your doctor about a referral to a Familial Cancer Clinic.