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

Published on September 20, 2022

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

To answer everything you’ve ever wondered about genetic breast cancer, Breast Cancer Trials (Australia’s largest oncology research group) is hosting an expert question and answer session.

Hosted by Australian political journalist, commentator and TV presenter Annabel Crabb, some of the country’s leading experts on genetic breast cancer will join breast cancer survivor Karen Alexander to discuss genetics, their relationship to breast cancer and current research.

Before the questions and answers, HerCanberra sat down with Breast Cancer Trials to ask a few questions.

Can you tell me what percentage of breast cancers are genetic?

It is believed that around 5-10% of breast cancer cases are hereditary if the gene mutation is passed directly from a parent.

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

If someone has a genetic mutation that “causes breast cancer,” what are the chances of them passing it on to their children? And her grandchildren?

Both women and men who have inherited an abnormal breast cancer gene have a 50% risk (or a 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 around 1 in 400 women in Australia today is at highest risk of breast cancer because she carries a BRCA1 or BRCA2 gene mutation. For these people, carrying a BRCA1 gene mutation is associated with an approximately 72% risk of developing breast cancer in their lifetime. And they can have up to a 44% risk of developing ovarian cancer. BRCA2 is associated with an approximately 69% chance of breast cancer and a 17% chance of ovarian cancer in life.

Jewish women of Eastern European (Ashkenazi) descent are more likely to carry a BRCA1 or BRCA2 gene mutation, which is estimated to be present in about 1 in 40 women. This is 20 times more common than in the general population.

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

Genetic testing is often offered to women who are diagnosed with breast cancer at an early age (35 years and younger), who have a strong family history, or who are diagnosed with certain types of breast cancer, such as “triple negative breast cancer.” When a gene mutation is identified, such as in BRCA1 or BRCA2 (the most common types), it can be linked to a family history of breast, ovarian, prostate, and some other cancers. It is important to note that family history can come from the maternal or paternal side of the family.

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

Genetic testing is only offered by a family cancer clinic or a suitably qualified professional such as an oncologist. When a woman is referred to a family cancer clinic, the availability, limitations, potential benefits, and possible consequences of genetic testing are discussed with her. If you’re concerned about a strong family history of breast cancer, or you have a close family member with a BRCA gene mutation, talk to your doctor about referring you to a family cancer clinic.