FRIDAY, Nov. 4 (HealthDay News) -- A widely used breast cancer test may not be accurate in identifying a gene that is critical in determining which life-saving treatment a woman should get.
The Oncotype DX, marketed by Genomic Health, results in a number of false-negatives for the HER2 gene, according to a study published Oct. 18 in the Journal of Clinical Oncology.
Women who test positive for the gene typically receive the targeted therapy Herceptin (trastuzumab) along with other medications to reduce their chances of recurrence and death.
"Women could be getting the completely wrong treatment," said study lead author Dr. David J. Dabbs, a professor and chief of pathology at Magee-Womens Hospital of the University of Pittsburgh Medical Center.
But, according to Dr. Lori J. Goldstein, director of the Breast Evaluation Center at Fox Chase Cancer Center in Philadelphia, the Oncotype DX test, which actually measures 21 different genes, was not designed to test for HER2, nor is it intended as a substitute for two other widely used and accepted lab tests.
"None of us would request Oncotype for the sole purpose of getting HER2," she said. "We're usually ordering it for other reasons and, as part of that test, we get HER2."
Oncotype has been shown to be reliable in identifying estrogen receptor-positive and progesterone-positive tumors, she added.
The only two valid assays for HER2 are immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH). Both are approved by the U.S. Food and Drug Administration (FDA).
Genomic's Oncotype employs reverse transcription polymerase chain reaction (RT-PCR) to check for HER2.
HER2 is overactive in 15 percent to 20 percent of breast cancers and usually signals more aggressive disease, according to background information in the study.
To test the accuracy of Oncotype DX in assessin
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