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Direct-to-Consumer Test Finds Rare Mutations in BRCA Breast Cancer Genes

A negative result in the 23andMe test doesn’t rule out increased cancer risk

The FDA has approved the first direct-to-consumer test that can warn users of their increased risk of breast, ovarian, or prostate cancer, but only a small percentage of Americans can reap any benefit.

The Personal Genome Service Genetic Health Risk Report for BRCA1/BRCA2 (Selected Variants), marketed by 23andMe, targets specific BRCA1/BRCA2 breast cancer gene mutations that are most common in people of Ashkenazi (Eastern European) Jewish descent. These three mutations, however, are not the most common BRCA1/BRCA2 mutations in the general population.

The test analyzes DNA collected from a self-collected saliva sample. The report describes if a woman is at increased risk of developing breast and ovarian cancer, and if a man is at increased risk of developing breast cancer or may be at increased risk of developing prostate cancer. The test detects three out of more than 1,000 known BRCA mutations. This means a negative result does not rule out the possibility that an individual carries other BRCA mutations that increase cancer risk.

“This test provides information to certain individuals who may be at increased breast, ovarian, or prostate cancer risk and who might not otherwise get genetic screening, and is a step forward in the availability of [direct-to-consumer] genetic tests. But it has a lot of caveats,” said Donald St. Pierre, acting director of the Office of In Vitro Diagnostics and Radiological Health in the FDA’s Center for Devices and Radiological Health.

“While the detection of a BRCA mutation on this test does indicate an increased risk, only a small percentage of Americans carry one of these three mutations, and most BRCA mutations that increase an individual’s risk are not detected by this test,” St. Pierre added. “The test should not be used as a substitute for seeing your doctor for cancer screenings or counseling on genetic and lifestyle factors that can increase or decrease cancer risk.”

Consumers and health care professionals should not use the test results to determine any treatments, including antihormone therapies and prophylactic removal of the breasts or ovaries. Such decisions require confirmatory testing and genetic counseling. The test also does not provide information on a person’s overall risk of developing any type of cancer. The use of the test carries significant risks if individuals use the test results without consulting a physician or genetic counselor.

The three BRCA1/BRCA2 hereditary mutations detected by the test are present in about 2% of Ashkenazi Jewish women, according to a National Cancer Institute study, but rarely occur (0% to 0.1%) in other ethnic populations. All individuals, whether they are of Ashkenazi Jewish descent or not, may have other mutations in BRCA1 or BRCA2 genes, or other cancer-related gene mutations that are not detected by this test. For this reason, a negative test result could still mean that a person has an increased risk of cancer due to gene mutations. 

Additionally, most cases of cancer are not caused by hereditary gene mutations but are thought to be caused by a wide variety of factors, including smoking, obesity, hormone use, and other lifestyle issues. For all of these reasons, it is important for patients to consult their health care professional who can help them understand how these factors impact their individual cancer risk and what they can do to modify that risk.

The FDA’s review of the test determined among other things that the company provided sufficient data to show that the test is accurate (i.e., can correctly identify the three genetic variants in saliva samples), and can provide reproducible results. The company submitted data on user comprehension studies, using representative genetic health risk test reports, that showed instructions and reports were generally easy to follow and understood by a consumer. The test report provides information describing what the results might mean, how to interpret results, and where additional information about the results may be found.

The FDA reviewed data for the test through the de novo premarket review pathway, a regulatory pathway for novel, low-to-moderate-risk devices that are not substantially equivalent to an already legally marketed device. Along with this authorization, the FDA is establishing criteria, called special controls, which set forth the agency’s expectations in assuring the test’s accuracy, reproducibility, clinical performance, and labeling. These special controls, when met along with general controls, provide reasonable assurance of safety and effectiveness for this test.

Source: FDA; March 6, 2018.

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