The full story behind BRCA1 and BRCA2

Everyone has BRCA1 and BRCA2 genes, says Prof Justus Apffelstaedt, Head of the Breast Clinic: Tygerberg Hospital and Associate Professor: University of Stellenbosch.

The function of BRCA genes, he explains, is to repair cell damage and keep breast cells growing normally; but when these genes contain abnormalities or mutations that are passed from generation to generation, the genes don't function normally and the risk of breast cancer 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 it. This is because normal BRCA genes help suppress tumours, but when they mutate, they don't assist in preventing uncontrolled growth. A study suggests that women with a faulty BRCA1 gene typically have a 45 to 90 % risk of developing breast cancer during their life, compared to a 12 % 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 8 % by the time they're 80 years old, which is about 80 times greater than average.

You are more likely to have an abnormal breast cancer gene if:

• You have first-line blood relatives (a mother or 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.

Mutations in BRCA1 and BRCA2 only cause about one in 20 cases of breast cancer, so just because you don't have the gene mutation doesn't mean you're immune. In fact 70 to 80% of women who have breast cancer have no family history of the disease. Although less than 10% of the population have the BRCA gene mutation, 50 to 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 %.

Patients need to realise this is a life-changing procedure. For example, it's not possible to breast feed after a mastectomy, and it does not guarantee a cancer-free future as you cannot remove all breast tissue during surgery.

• [email protected]; www.apffelstaedt.com