Genetics and Family History
Although breast cancer is very common and many families may have a relative who has developed breast cancer, most breast cancers do not have a strong link to an inherited gene. Only about 5 to 10% of breast cancers are caused by a gene passed down from a parent. This can be your mother or father so obtaining a history on both sides of the family is important. These cancers are usually seen in a family where multiple relatives, often at a young age (under 50) have developed breast cancer. It may be suspected in families where there are other cancers such as ovarian cancer or pancreatic cancer. There is also more risk of an abnormal gene in the family if a male gets breast cancer or in families with Ashkenazy Jewish heritage.
We can test for abnormalities in genes (mutations) by obtaining a small sample of blood or saliva and analysing the DNA. A range of commercially available tests are around and at BreastCare we offer the Color gene mutation test which analyses up to 30 different genes, 12 of which are directly related to breast cancer risk.
Patients should receive genetic counselling before proceeding with a test. If they have a positive test for a gene mutation then further counselling and specialist surgical advice should be sort. Patients may also benefit from seeing a psychologist. A large proportion of patients having genetic testing will have a negative test despite a strong family history. These patients are likely to have genetic factors that we don’t fully understand yet.
The most common gene mutations we see in familial breast cancer are BRCA1 and BRCA2 gene mutations. Although everyone has two copies of these genes, which help repair your DNA, if there is a fault in one of these genes (mutation ) then there can be an increased risk of getting different types of cancer including breast cancer. BRCA1 carries a risk of around 50% or more of getting breast cancer and also an increased risk of getting ovarian cancer. The risk for BRCA2 is a little less but similar. Men carrying these gene mutations also have an increased cancer risk including breast cancer.
For such patients, at a minimum increased breast screening is recommended including, particularly for younger patients, breast MRI. Other options for managing a patient’s risk if they have a mutation include going onto a medication such as Tamoxifen to reduce, by up to 50%, the risk of developing breast cancer. Many patients may choose prophylactic surgery which commonly involves mastectomy, often combined with reconstruction. Performing mastectomies to remove all the breast tissue can reduce the risk of developing breast cancer by over 95%. If you are a gene mutation carrier, or have a strong family history of breast cancer, then you should discuss these management options with the doctor looking after you at BreastCare.
