We hear a lot about their link to breast cancer, but just what are BRCA1 and BRCA2 genes? Dr Justus Apffelstaedt explains…
Its Breast Cancer Awareness month and that means everyone is going to be talking about prevention, detection and BRCA1 and BRCA2 genes’ link to breast cancer.
What you might know about BRCA1 and BRCA2 genes is that everyone has them.
What are BRCA1 and BRCA2 genes?
The function of the BRCA genes is to repair cell damage and keep breast cells growing normally.
However, when these genes contain abnormalities or mutations that are passed from generation to generation, the genes don’t function normally and breast cancer risk increases, as they no longer assist in preventing uncontrolled growth of tumours.
Women carrying mutations of the BRCA genes are about five times more likely to develop breast cancer than those without. This is because normal BRCA genes help suppress tumours, but when they’re mutated they don’t assist in preventing uncontrolled growth.
A study suggests that women with a faulty BRCA1 gene typically have a 45 – 90 percent risk of getting breast cancer during their life, compared to a 12 percent risk for the average woman.
Women with an abnormal BRCA1 or BRCA2 gene also have an increased risk of developing ovarian, colon, pancreatic, and thyroid cancers, as well as melanoma.
Men who have an abnormal BRCA2 gene have a higher risk for breast cancer than men who don’t – about eight percent by the time they’re 80 years old, which is about 80 times greater than average.
How do you know if you have abnormal BRCA1 or BRCA2 genes?
You are substantially more likely to have an abnormal breast cancer gene if:
- You have first-line blood relatives (mother, sisters, who had breast cancer diagnosed before age 50.
- There is both breast and ovarian cancer in your family, particularly in a single individual.
- Women in your family have had cancer in both breasts.
- A man in your family has had breast cancer.
- You are of Ashkenazi Jewish (Eastern European) heritage.
About 70 – 80 percent of women who have breast cancer have no family history of the disease
However, mutations in BRCA1 and BRCA2 only cause about one in twenty breast cancers.
In other words, just because you don’t have the gene mutation doesn’t mean you’re immune.
In fact, 70 – 80 percent of women who have breast cancer have no family history of the disease.
You can get tested
Although less than 10% of the population have the BRCA gene mutation, 50-80% of these women have a chance of developing breast cancer.
In South Africa, the test for the BRCA1 and BRCA2 genes has been commercially available to the general public since 2005. A blood sample is required for these tests, and genetic counselling is recommended before and after the tests.
A positive test result in BRCA1 or BRCA2 means that the person has a genetic mutation that increases cancer risk. A positive BRCA1 result gives a woman a 60% to 80% lifetime risk of breast cancer and a 30% to 45% lifetime risk of ovarian cancer. A positive BRCA2 result gives a woman a 50% to 70% lifetime risk of breast cancer and a 10% to 20% lifetime risk of ovarian cancer.
If the results are positive the person can be continuously monitored to ensure early detection of breast cancer if it arises, or they could undergo a mastectomy, which will reduce the risk of breast cancer by up to 90 percent.
Patients need to realise this is a life-changing procedure, for example, it’s not possible to breastfeed after a mastectomy, and it does not guarantee a cancer-free future as you cannot remove all breast tissue during surgery.
Dr Justus Apffelstaedt is a specialist surgeon with an interest in breast, thyroid and parathyroid health as well as soft tissue surgical oncology.
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