Breast cancer, like other cancers, develops when changes occur in genes in breast cells. In that sense, all breast cancer has a genetic element. But, genetic does not mean inherited. Only an estimated 5-10 percent of breast cancer cases result from an inherited genetic predisposition to the disease. In other words, more than 90 percent of all breast cancer cases result from factors that are not inherited and, in many cases, are unknown.
BRCA1 and BRCA2
So far, researchers have found two genes linked with breast cancer — labeled BRCA1 and BRCA2 — that everyone inherits in pairs: one from our mother and one from our father. When they function normally, they are supposed to stop the growth of cancerous cells in the breast. When both genes in a pair are damaged, they don’t work properly and cancer may develop. People who inherit a damaged BRCA1 or BRCA2 gene from one parent are at much greater risk of developing breast, pancreatic and ovarian cancers than people who inherit two normal genes.
Blood tests have been developed –and are now marketed commercially — that can identify BRCA1/2 gene mutations.
What is the Risk of Getting Cancer if I Test Positive for BRCA1 or BRCA2 mutations?
Breast Cancer: About 12 percent of women in the general population will develop breast cancer sometime during their lives. A large 2017 study estimated that about 72 percent of women who carry a harmful BRCA1 mutation and 69 percent of those with a harmful BRCA2 mutation will develop breast cancer by age 80.
Ovarian cancer: About 1.4 percent of women in the general population will develop ovarian cancer sometime during their lives. The study mentioned above estimated that about 44% of women who inherit a harmful BRCA1 mutation and about 17% of women who inherit a harmful BRCA2 mutation will develop ovarian cancer by the age of 80.
Should I Get Tested?
It’s important to consider the family history of breast and ovarian cancer from both your mother’s and your father’s sides of the family. Genetic testing should be considered only in limited circumstances. It is usually recommended that individuals with breast and/or ovarian cancer undergo testing for BRCA mutations because if the results are negative, their children would not need to be tested. Individuals without breast and/or ovarian cancer who are most likely to benefit from genetic testing are those of us who believe—because of a family history of two or more first-degree relatives (such as a mother or sister) with breast and/or ovarian cancer—that we may be mutation carriers and, if so, want to attempt to reduce our cancer risk.
All genetic testing should be accompanied by written, informed consent; complete information about benefits and risks; and professional counseling about options. This is best done through one of the many cancer risk assessment programs located throughout the country. A comprehensive list of programs can be found on the websites of the National Society of Genetic Counselors and American Board of Genetic Counseling.
We need to approach genetic testing with caution until science can tell us more about what the results mean and public policy can protect us from discrimination in employment, insurance coverage or other areas on the basis of genetic information.
What Are My Options if I Test Positive for BRCA Mutations?
If you have BRCA gene mutations, several possible strategies can reduce your risk of breast and ovarian cancer. These include taking drugs such as tamoxifen or raloxifene; prophylactic—that is, preventive—mastectomy; and having the fallopian tubes and ovaries removed.
Because the science behind these strategies is changing so rapidly, and because these are major decisions with important risks to consider, it’s best to consult experts, pursue the latest information about these options, and consider their possible effects on your life.
Women who are at increased risk of cancer can find a wealth of resources at FORCE: Facing Our Risk of Cancer Empowered.