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November 28, 2017

Testing for BRCA1/2 Mutations

JAMA. 2017;318(20):2054. doi:10.1001/jama.2017.17280

Changes in genes called BRCA1 and BRCA2 increase a person’s risk of certain types of cancer, especially cancers of the breast and ovaries.

BRCA1 and BRCA2 are types of tumor suppressor genes—genes that produce special proteins needed to repair damaged DNA (genetic material) in cells. Certain mutations (changes) in these genes prevent the repair of damaged DNA. In turn, the presence of unrepaired DNA increases the risk of acquiring other mutations that contribute to the development of cancer.

If you are a woman, harmful mutations in the BRCA1 or BRCA2 genes can greatly increase your risk of developing cancer of the breast or ovaries. Such mutations also can increase your risk of developing cancer of the fallopian tubes, peritoneum (lining of the abdominal cavity), or pancreas. If you are a man, such mutations can increase your risk of developing cancer of the breast, prostate, or pancreas. Some BRCA1/2 gene mutations, if inherited from both parents, are also associated with the development of certain forms of anemia in both women and men.

What Factors Influence the Chances of Having a Harmful BRCA1/2 Mutation?

A number of factors can increase your chances of having a harmful BRCA1 or BRCA2 mutation. The figure lists some of these factors. Your doctor or a genetic counselor can provide more information and help you understand these risk factors.

Who Should Be Tested for BRCA1/2 Mutations?

The harmful BRCA1/2 mutations that can lead to serious medical conditions are not common. If you do not already have cancer, you should consider being tested for such mutations if your personal or family medical history reveals factors such as those listed in the figure that make it likely that you might have a harmful BRCA1/2 mutation. Your doctor or a genetic counselor can review your personal and family medical histories and help you decide whether to be tested.

What Do the Test Results Mean?

A positive test result means that you do have a harmful BRCA1/2 mutation and your risk of developing certain cancers, especially of the breast or ovaries, is increased. In addition, a positive result suggests that other family members—such as brothers, sisters, or children—might also have a harmful BRCA1/2 mutation, and they should consider being tested. A positive result does not mean that you (or affected family members) definitely will develop cancer—but knowing that you have a harmful BRCA1/2 mutation can help you and your doctor develop a monitoring plan that helps minimize risks for you and your family members.

A negative test result means that you most likely do not have a harmful BRCA1/2 mutation—but the implications of that information depend on factors such as your personal and family medical histories. For example, if your personal or family histories suggest that you might be at risk of having a harmful BRCA1/2 mutation but no close relatives have been identified as having such a mutation, you might still have a BRCA1/2 mutation that was not identified by the test and that has not yet been identified as harmful. Your negative test result is considered true negative only if you also have a close relative identified as having a harmful BRCA1/2 mutation. However, a true-negative result does not mean that you definitely will not develop cancer. You still have an average overall risk of developing a cancer unrelated to BRCA1/2 mutations.

An uncertain (ambiguous) test result means that you do have a BRCA1/2 mutation, but the particular mutation has not been identified as contributing to cancer risk.

The interpretation of results of mutation testing is complex. Your doctor or a genetic counselor can help interpret results and also recommend specific action you should take, especially if you have received a positive test result.

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Article Information

Sources: Mayo Clinic, National Cancer Institute

Topic: Cancer Genetics