Several companies are marketing genetic testing that tests for up to 100 genes, including 20 genes that have been linked to breast cancer. But a group of researchers say that such gene panel testing may not be valid as yet and may not be useful for determining the care for a given patient who has these genes.
The best known genes that indicate an increased risk for breast cancer are BRCA1 and BRCA2. The clinical usefulness of testing for these genes is known because they are associated with a high risk of breast cancer and other cancers. However, the researchers looked at the many other genes in these tests that are not as well-understood as BRCA1 and BRCA2. Some of these genes are included in the gene panels as a way to generate data that can determine how much they increase the risk of disease. But the test results are then sent to physicians and patients who have to figure out what the results mean.
The report noted that gene tests can be marketed without having to show that they have any clinical validity or usefulness. The U.S. Food and Drug Administration is considering how to regulate diagnostic tests, which would include most if not all genetic tests. The report focused on the clinical validity of test for lesser-known breast cancer genes, but noted that there are similar questions about genes for other cancers.
"[T]he fact that the technology is available does not necessarily mean that such tests are appropriate or desirable," the authors wrote in their report, which was published in the New England Journal of Medicine. They are proposing that genetic tests not be offered until their validity has been established.
Health insurance companies are already questioning the usefulness of testing for large panels of genes. The U.S. Centers for Medicare and Medicaid Services is drafting a statement that says that large panel tests for BRCA genes that includes other genes not relevant to the patient are not reasonable or necessary.
