Approximately 5 to 10 per cent of breast cancers are due to inherited genetics (hereditary) factors. Some people carry a genetic mutation known as BRCA1 or BRCA2.

In people with an extensive family history of breast and/or ovarian cancer, or who have certain features of their cancer that may be hereditary, a breast cancer genetic test may be suggested or offered. Candidates for genetic testing may include:

• Women with family history of breast / ovarian cancer.

• Women with a family history of fallopian tube or peritoneal cancer.

Genetic testing for breast cancer in appropriate patients is a personal choice and for those who do go ahead with testing, it may help patients to take proactive steps to reduce their risk.

The BRCA1 and BRCA2 genes produce tumour suppressor proteins that help repair damaged DNA and in turn, play a role in the stability of the cell's genetic material. When these genes do not function normally, damaged cell DNA may not be repaired and could possibly lead to cancer. Some women may have a family history of BRCA1 or BRCA2 cancers, which could increase their risk of developing breast cancer. Together, these two types of mutations account for 20 to 25 per cent of hereditary breast cancers. 

A number of different genes have been associated with an increased risk of breast cancer, including TP53, PTEN,BRIP1, CDH1, CHEK2 and PALB2, MSH2, MLH1, MSH6, PMS2 and EPCAM. These genes are less well understood compared to BRCA1 and BRCA2, since they are rarer and haven’t been studied as much as the BRCA genes.

Talk to your doctor to better understand if you have any potential hereditary factors that could affect the growth or spread of your cancer. Knowing more about what is affecting the growth of the cancer gives doctors better direction on the best course of treatment.

Gene-based tests find differences between normal genes and genes that are changed (mutated) in cancer cells. Microarray analysis is a type of gene-based test that allows researchers to look at many genes together to see which ones are turned on and which ones are turned off. Analyzing many genes at the same time to see which are turned on and which are turned off is called gene expression profiling. Researchers hope that developing more gene-based tests will help doctors identify the best treatments for certain cancers, including breast cancer. Gene-based tests will also help doctors tailor more treatments to each person’s cancer based on their unique genetic makeup.