It’s not just the colour of your eyes and hair that you inherit from your parents and family tree. You also inherit genes which may determine your risk of certain diseases such as breast and ovarian cancer. Two of these genes are called BRCA1 and BRCA2.
To find out if you have an inherited risk of breast or ovarian cancer, you will need to undergo genetic testing, to establish whether there is a gene mutation. The genes most commonly tested are BRCA1 and BRCA2.
According to GP Dr Alia Kaderbhai around one in seven women in Australia have a lifetime risk of breast cancer (and 1.2% for ovarian cancer).i However, if there is a history of BRCA1 and BRCA2 gene in your family, the risk increases to about 60% to 70%. The BRCA1 and BRCA2 variants are evident in less than 3% of all breast cancers.
To test for genetic mutations, a patient will have genetic counselling, then a sample of blood is usually taken from a woman in the family who has developed breast cancer or ovarian cancer. The DNA is ‘searched’ for a gene fault or gene faults. This testing can take from a few weeks to a few months.
“If a ‘fault’ is detected, all family members should be notified and offered testing,” says Dr Kaderbhai. “This is called ‘predictive genetic testing’.”
Dr Kaderbhai says that it’s vital that a complete family history of both sides of the family is taken; both the mother and father’s family history. “When taking a medical history, the significance of a family history of breast cancer increases with the number of family members affected, how young they were at the age of diagnosis,” she says. “The younger a relative was when they were diagnosed, the more likely it was that they developed cancer due to hereditary factors.”
The factors which can increase the risk of carrying a pathogenic BRCA1 or BRCA2 variant include:
· Multiple numbers of relatives on the same side of the family (maternal or paternal) who have had breast or ovarian cancer
· A family member has been diagnosed with breast AND ovarian cancer
· A diagnosis in a family member under the age of 40 years
· The family has Ashkenazi Jewish ancestry (from central and easter Europe)
· A family member has been diagnosed with bilateral breast cancer
· A male family member has been diagnosed with male breast cancer.
It’s important to remember that even if there is a history of breast or ovarian cancer in your family, you may not have inherited the gene. This is why genetic testing is so important.
Tracing your family health tree
To begin mapping the genetic history of your family, you will need to go back three generations. This is key to identifying high-risk families who are most likely to benefit from genetic testing. It’s best to have this conversation as a family, or to encourage family members to visit their GP, so that all family members can contribute and even fill in the medical gaps of generational history.
Breast cancer survivor Lan Cowley says its vitally important for families to know their medical history. “Having gone through a cancer diagnosis and its aftermath, early intervention is more than just survival. If you can prevent (or reduce the risk of) a cancer diagnosis, you’ll avoid treatment. Knowing your risk and that of your loved ones is power to you. It's important to take charge of your health.