Undergoing genetic testing for breast cancer is like consulting a foggy crystal ball: You can walk away with a vague idea of what might happen, but not the full picture. Having a mutation for the disease is no guarantee you’ll get it—and a negative result doesn’t necessarily mean you’re in the clear. Only about 5 to 10 percent of breast cancers are hereditary; the rest are caused by sporadic mutations that a test can’t predict. If you have certain risk factors, however, testing can yield critical information.
Testing identifies irregularities in your DNA, the blueprint that tells your body how to build cells. For the most part, we all share the same DNA, but each of us inherits some mistakes, called mutations, from our parents. Over the years, scientists have identified specific genes that, when they mutate, put people at higher risk for certain diseases.
The most well-known of these genes are BRCA1 (as in breast cancer 1) and BRCA2. People with a BRCA1 mutation, on average, have a 55 to 65 percent chance of getting breast cancer; with a BRCA2 mutation, the risk is around 45 percent.
Scientists have also linked breast cancer with the gene PALB2, a partner gene of BRCA2 that tells cells to produce proteins that help repair damaged DNA. Someone with an abnormal PALB2 is five to nine times more likely to get breast cancer. Though several other mutations are linked to the disease, BRCA mutations remain the most common cause of hereditary breast cancers.
But because BRCA1 and BRCA2 mutations are relatively rare, the U.S. Preventive Services Task Force recommends the test only for those who, after screening and counseling, have been found to have a family history that puts them at significant risk—which includes having female relatives (mother, sister, aunt, grandmother) who’ve had breast cancer or cancer of the ovaries, fallopian tubes, or abdominal lining (a BRCA mutation is linked to higher risk of those cancers, too) or who got breast cancer before age 50. You’re also more likely to have a BRCA mutation if you’re related to a man who’s had breast cancer; people of Jewish Eastern European ancestry are more prone to the mutation, too. If you have none of these risk factors, testing isn’t recommended since it’s highly unlikely you’ve inherited a mutated gene.
If you’re considering genetic testing, talk to your doctor and a specially trained genetic counselor. The process, which requires blood or saliva samples that may take two to four weeks to analyze, can be difficult without someone to guide you through it. Your counselor can connect you with a trusted lab and may arrange testing for other mutations in addition to BRCA1 and BRCA2; she can also interpret and explain your results.
One option for those who have a BRCA1 or BRCA2 mutation is breast removal. However, another is close monitoring through annual MRIs and mammograms and biannual clinical breast exams. If you have another breast cancer–related mutation, your doctor may recommend more frequent checkups or lifestyle changes that lower your risk.
Genetic tests can’t predict what will happen, but they can help you plan for the road ahead. With a counselor’s guidance, you’ll feel empowered by what you learn.
Mehmet Oz, MD, is the host of The Dr. Oz Show (weekdays; check local listings).