The link between genetics and breast cancer

• As well as age and health history, genetics and family history influence breast cancer risk, which doubles in women with an affected close relative, according to Cleveland Clinic.

The specific cause of breast cancer is unknown; however, certain factors can put a person at greater risk of developing the disease, such as age, ethnicity and personal health history, among others.

Another important factor to consider is genetic make-up and family history. Genetics plays a dominant role in planning breast cancer treatment. Where appropriate, family-based risk assessments and genetic testing can provide a basic understanding of the structure and function of genes and determine the best treatment option.

According to Cleveland Clinic, breast cancer risk doubles for women who have a close relative who has had breast cancer: about 20 to 30 per cent of women diagnosed with breast cancer have a relative who has also had it. However, up to 80 per cent of women diagnosed with breast cancer have no family history, and the cancer is believed to occur because of genetic abnormalities resulting from the natural ageing process. About 5-10 per cent of breast cancers are linked to genetic mutations a woman inherits from her mother or father.

The most common genes associated with hereditary breast cancer risk are BRCA1 and BRCA2. A blood test is needed to determine whether a patient carries either of these genes, with results typically available within a few weeks.

“During a genetic counselling visit at Cleveland Clinic, a counsellor will take a personal medical history and a detailed family medical history. That will determine whether or not genetic testing is appropriate and which genetic changes to test for,” said Cassan Blake, M.D., a breast surgical oncologist at Cleveland Clinic Florida. “We also offer predictive testing for family members who may have inherited a specific genetic mutation.”

For most people, breast cancer is a disease that affects women, but men can also develop it. Although breast cancer in men is rare (less than 1% of all new breast cancer cases), men can develop the same types of breast cancer as women because of the small amount of breast tissue they have. Risk factors for men are similar to those for women, but also include others such as testicular conditions, oestrogen exposure and Klinefelter syndrome, a congenital condition that affects about 1 in 1,000 men.

The risk of breast cancer in men increases with age, and it is commonly diagnosed between the ages of 50 and 70. Cancers linked to genetic mutations often occur in people under 60. The symptoms of breast cancer in men are very similar to those in women. However, tumours are usually smaller but may be more advanced at diagnosis, because men have very little breast tissue, so the tumour does not have much room to grow before invading other tissues or the lymph nodes.

For both women and men with a strong family history of breast cancer, it is important to do monthly self-examinations and have any change checked by a doctor immediately. It is important to share whether there is a family history of breast cancer and discuss whether that history might warrant changes in care.