What does an ambiguous BRCA1 or BRCA2 test result mean?
Sometimes, a genetic test finds a change in BRCA1 or BRCA2 that has not been previously associated with cancer. This type of test result may be described as “ambiguous” (often referred to as “a genetic variant of uncertain significance”) because it isn’t known whether the gene change affects a person’s risk of developing cancer.
One study found that 10% of women who underwent BRCA1 and BRCA2 mutation testing had this type of ambiguous result.16 As more research is conducted and more people are tested for BRCA1 and BRCA2 mutations, scientists will learn more about these changes and cancer risk. Genetic counseling can help a person understand what an ambiguous change in BRCA1 or BRCA2 may mean in terms of cancer risk.
How can a person who has a positive test result manage their risk of cancer?
Several options are available for managing cancer risk in individuals who have a known harmful BRCA1 or BRCA2 mutation. These include enhanced screening, prophylactic (risk-reducing) surgery, and chemoprevention.
Enhanced Screening. Some women who test positive for BRCA1 and BRCA2 mutations may choose to start screening at younger ages than the general population or have more frequent screening. For example, some experts recommend that women who carry a harmful BRCA1 or BRCA2 mutation undergo clinical breast examinations beginning at age 25 to 35 years.17 And some expert groups recommend that women who carry such a mutation have a mammogram every year, beginning at age 25 to 35 years.
Enhanced screening may increase the chance of detecting breast cancer at an early stage, when it may have a better chance of being treated successfully.
However, women who carry mutations in BRCA1 and BRCA2 may be more likely to develop radiation-associated breast cancer than women in the general population because those genes are involved in the repair of DNA breaks, which can be caused by exposure to radiation.
Women who have a positive test result should ask their health care provider about the risks of diagnostic tests that involve radiation (mammograms or x-rays). Recent studies have shown that MRI may be more sensitive than mammography for women at high risk of breast cancer.18,19
However, mammography can identify some breast cancers that are not identified by MRI (20), and MRI may be less specific (i.e., lead to more false-positive results) than mammography. Several organizations, such as the American Cancer Society and the National Comprehensive Cancer Network, now recommend annual screening with mammography and MRI for women who have a high risk of breast cancer.
No effective methods of ovarian cancer screening currently exist. Some groups recommend transvaginal ultrasound examinations, blood tests for the antigen CA-125, and clinical examinations for ovarian cancer screening in women with harmful BRCA1 or BRCA2 mutations, but none of these methods appears to detect ovarian tumors at an early enough stage to reduce the risk of dying from ovarian cancer.21
The benefits of screening for breast and other cancers in men who carry harmful mutations in BRCA1 or BRCA2 is also not known, but some expert groups recommend that men who are known to carry a harmful mutation undergo regular mammography as well as testing for prostate cancer.