Approximately 1 in 15 cases of breast cancer are considered to be caused by a gene mutation inherited from a parent, known as hereditary or familial breast cancer.
Some people develop mutations in the genes that are linked to causing breast cancer and do not have a family history of the disease. Therefore, it appears that the gene mutation can also be acquired and not solely based on inheritance.
Family History and Breast Cancer Risk
Women who have a family history of breast cancer are more likely to be affected by breast cancer themselves.
Any woman who has two of more blood relatives (on the maternal or paternal side) such as a grandmother, mother, aunt, or sister who has been diagnosed with breast cancer can be considered to have a family history of the disease. If they have several blood relatives who have been diagnosed with breast cancer, they are considered to have a strong family history and an increased risk of being diagnosed with the condition themselves.
The risk of breast cancer also depends on the age and nature of diagnosis of the other family members who were affected. In particular, families who have had a diagnosis of breast cancer in individuals under the age of 50, or in conjunction with ovarian cancer, are more likely to be affected.
There are several genes that can be inherited that may be responsible for causing breast or ovarian cancer. These genes are usually involved in the production of proteins that regulate cell growth and replication in the breasts. Therefore, a mutation in the gene that interferes with its function could lead to uncontrolled cell growth and breast cancer.
A mutation in the BRCA1 or BRCA2 gene is known to be linked to an increased risk of developing breast cancer. There are genetic tests available that can detect whether an individual is a carrier of the gene mutation and, hence at an increased risk of developing breast cancer. These tests are not routinely recommended to all members of the population but can be arranged at a familial cancer center for individuals who have a family history of breast cancer.
There are also various other genes that are associated with an increased risk of breast cancer and other cancers. There include the ATM, CDH1, CHEK2, MRE11A, NBN, PALB2, PTEN, RAD50, RAD51C, and TP53 genes.
Finally, there are some women with a strong family history of breast cancer who do not test positive for any of the genes known to be associated with breast cancer. In some cases, this may be due to an inherited gene that is causing hereditary cancer that has not yet been identified in scientific research.
Individual Who Carry a Gene Mutation
An individual who inherits a gene mutation that is linked to an increased risk of breast cancer is not guaranteed to develop cancer. In fact, it can be useful for them to be aware of the mutation so that they can be proactive about breast cancer prevention and early detection.
Firstly, there are several things that affected individuals can do to reduce their risk of developing breast cancer. These include to the following:
- Keep physically active
- Maintain a healthy weight
- Consume a nutritious diet with high intake of fresh fruit and vegetables
- Avoid or quit smoking
- Moderate intake of alcohol
It is recommended for gene carriers to undertake regular breast examinations to check for signs of abnormal growth. If they notice any change in the size or shape of the breast or the development of a lump, they should see a medical professional to seek further advice and undergo appropriate testing, if necessary.
Regular breast cancer screening with a mammogram is recommended for all women over the age of 50, but may also be useful for younger women if they are a carrier of a breast cancer gene mutation. Women with a strong family history of breast cancer but no known gene mutation may also be recommended to have screening tests from an earlier age.
In some cases, women who carry a gene associated with breast cancer may choose to undergo prophylactic treatment to reduce the risk that she will be affected. There are various options to help prevent the development of breast cancer, including hormonal therapies, such as selective estrogen receptor modulators (SERMs) or aromatase inhibitors, to reduce the risk of hormone-receptor-positive cancer. For some women who do not wish to bear children in the future, removal of the ovaries may be an option.
Reviewed by Susha Cheriyedath, MSc