Breast Cancer Gene Testing
Making the decision to find out about your inherited susceptibility for developing breast cancer may be difficult. It is important to understand what genetic risk is and how it may affect you.
Many people think that breast cancer is passed on in families, but in most cases it isn't. More than 70% of women diagnosed with breast cancer have no family history of the disease, and a further 20% to 25% have risk factors that are not genetic. This means that 5% to 8% of all breast cancers diagnosed are caused by a damaged gene that is passed on in families. The best known and most common damaged genes are BRCA1 and BRCA2 (the first and second Breast Cancer genes identified).
Specific characteristics of your family’s cancer history could indicate the presence of a BRCA genetic alteration if you:
- have one or more first-degree female relatives (mother, sister, daughter) who have had premenopausal breast cancer at a young age.
- have one or more first-degree male relatives (father, brother, son) who had breast cancer.
- have one or more first-degree female relatives who have had premenopausal bilateral (both breasts) breast cancer.
- have one or more first-degree female relatives who have had premenopausal ovarian cancer.
- are Ashkenazi Jewish and have a family history of breast cancer.
Only you and your doctor can determine if genetic testing is the right option for you. Many large hospitals have clinics where you can talk with a counselor who can help you assess your genetic risk. One of these counselors can help determine the likelihood that you carry a genetic alteration.
Deciding to have the gene test has many implications, including:
- the affect on other family members
- access to insurance
- possible job discrimination
- the possibility of finding out that you carry the gene (when other family members don't) or that you don't (when other family members do).
A genetic counselor can help you anticipate and deal with these implications.
While a lot is known about the BRCA1 and BRCA2 gene mutations, potentially hundreds of mutated genes are yet to be discovered. If you choose to have a genetic test, the laboratory will look for known genetic alterations and for specific mutations in families, which may not be present in the population at large. Although this testing is very effective, it is still limited by our current knowledge.
Alterations in the BRCA1 and BRCA2 genes can predispose carriers to breast cancer in both men and women, ovarian cancer in women, and prostate cancer in men. Should you test positive, be sure to talk with your physician about monitoring your health and screening for these types of cancers.
An excellent booklet on this topic is, "Genetic Testing for Breast Cancer Risk: It's Your Choice" (November 1997), which was developed by the National Action Plan on Breast Cancer. You can download a copy at the National Cancer Institute Web site www.cancer.gov.