Test frequently
fails to spot gene mutation linked to breast cancer

A genetic test marketed by Myriad Genetics that screens for the BRCA1 and BRCA2 genetic mutations that are linked with increased risk of breast cancer fails to identify the mutations in about 12% of women who have been diagnosed with breast cancer, have a family history of the disease or of ovarian cancer, or who have previously tested negative for the mutations, The New York Times reports. The test is the only one of its kind on the U.S. market and costs about $3,000. About 1 in 400 people are believed to carry the genetic mutations, which research has shown boosts the chances of developing breast and ovarian cancers.

But now a study in the March 22 issue of the Journal of the American Medical Association, conducted by researchers at the University of Washington, shows that the test returns a high number of false-negative results. The researchers examined 297 women and three men who had previously tested negative for the genetic mutations and who either had been diagnosed with breast cancer or had at least four family members previously diagnosed with breast or ovarian cancer. Using more advance testing methods not commercially available in the United States, the researchers found that 35 of the study subjects--12%--carried either the BRCA1 mutation, the BRCA2 mutation, or both.

Some cancer experts say they have been aware that the Myriad test may miss identifying some genetic mutations but say this is the first study to determine the actual false-negative rate. They also worry that Myriad's monopoly of the U.S. testing market may be hindering research into better BRCA mutation diagnostic tests.

"What [this study] really points to is that if women with a strong family history have been tested and have been told we didn't find a gene mutation, we shouldn't stop there," Julie Gralow, an oncologist at the Seattle Cancer Care Alliance, told the Seattle Post-Intelligencer. "We need an open and competitive marketplace for the development of genetic testing."

Gregory Critchfield, president of Myriad's genetic testing division, told The New York Times the company continues to fund research and development of better BRCA tests, adding that Myriad hopes to have a more sensitive test available on the market later this year. (The Advocate)