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BRCA testing update
Getting Better Results from Genetic Testing
Women with strong family histories of breast cancer who receive negative (or normal) genetic tests for BRCA1 and BRCA2 may still be at high risk, according to a study in the Journal of the American Medical Association (March 22). That's because current testing techniques identify only a handful of certain types of the genetic mutations known to cause breast cancer.
Currently in the United States, genetic testing for BRCA1 and BRCA2 is carried out by a single commercial firm, Myriad Genetics Inc., in Salt Lake City. The type of testing that Myriad uses, called sequencing, searches for only five of the most common large rearrangement mutations.
However, over the last several years scientists have discovered many more. To identify them, researchers say, Myriad would have to use a global screening technology, which catches harder-to-spot genetic rearrangements. Because that technology has not yet met clinical standards, Myriad has not used it, says Bill Hockett, executive vice president of communications for the company.
In the JAMA study, researchers looked at 300 breast cancer patients who had strong family histories of breast or ovarian cancer—which would suggest the presence of genetic mutations—but who had normal genetic testing results when sequencing alone was performed. Using multiple screening methods, the researchers found previously unidentified BRCA mutations in 12 percent of the patients.
Later this year Myriad plans to broaden its testing methods in order to detect more of the gene mutations that contribute to breast cancer.
Until then, Mary-Claire King, one of the study's authors, advises women with a strong family history of breast cancer who previously tested negative for the disease to assume that they do have a mutation, but one that science hasn't yet figured out how to identify.
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