People talk about how cancers “run in the family” and seem to pass from one generation to the next. Although many people think this is the most common cause of breast cancer, research shows that just 5 to 10 per cent of breast cancers are hereditary. However, if you have close family members who have been diagnosed with breast cancer, you may have an increased risk of developing the disease.
Signs of hereditary breast cancer
Family histories that may suggest an increased risk of breast cancer include the following:
Family members diagnosed with breast cancer before age 35.
Family members diagnosed with ovarian cancer at any age.
Several family members, including from different generations, diagnosed with breast or ovarian cancer.
A male family member with breast cancer.
Family members who have been diagnosed with breast cancer in both breasts or with breast and ovarian cancer.
Ashkenazi Jewish ancestry.
Gene mutations
BRCA 1 and BRCA 2 are genes that normally help protect us from getting breast cancer. However, if you have an abnormality or mutation in one copy of your BRCA 1 or BRCA 2 gene, your risk of developing breast cancer is much greater than for people who do not.
Not all gene mutations are harmful, but it is estimated that about 60 per cent of women who have inherited a BRCA 1 or BRCA 2 mutation are at risk of developing breast cancer.
Several methods are available to test for BRCA 1 and BRCA 2 and other known genetic mutations that are linked to breast cancer.
Reducing your risk
If you think you may have a family history of breast cancer, the Canadian Breast Cancer Foundation encourages you to speak to a health care provider about your family’s cancer history, your breast cancer risk and how to access genetic counselling and genetic testing, as well as options for screening your breast health for the earlier detection of breast cancer.
Established risk factors
Sources
Canadian Breast Cancer Foundation – Ontario Region. (2010). Earlier Detection and Diagnosis of Breast Cancer: A Report from It’s About Time! A Consensus Conference.
National Cancer Institute. BRCA1 and BRCA2: Cancer Risk and Genetic Testing. Accessed July 31, 2011.
University Health Network. What is hereditary cancer? Accessed July 31, 2011.