New HER2 Testing Guidelines
December 20, 2006 - According to findings from a new study published in this month's Journal of Clinical Oncology (JCO), approximately 20 percent of current HER2 (human epidermal growth factor receptor 2) testing may be inaccurate. However, researchers reported that when carefully validated testing is conducted, "available data do not clearly demonstrate the superiority of either immunohistochemistry (IHC) or in situ hybridization (FISH) as a predictor of benefit from anti-HER2 therapy."
The HER2 protein, which promotes cancer cell growth, is present in approximately 25 percent to 30 percent of breast cancer patients' cells, and over expression of this protein is associated with a poor prognosis and a shortened survival.
HER2 Status Helps Determine Treatment Options
Breast cancer is said to be HER2-positive if the HER2 protein is over expressed, or overabundant, in its cells, or HER2-negative if the HER2 protein levels are normal. Women whose cancer cells contain too many copies of the HER2 gene are candidates for trastuzumab (Herceptin®) therapy; therefore, reliable detection of HER2 over expression (IHC) or amplification (FISH) is important for the success of Herceptin therapy.
IHC, the most frequently used method for measuring HER2, measures HER2 protein over expression. Historically, IHC has been used in clinical trials of women with breast cancer receiving Herceptin. FISH is a diagnostic test that measures the number of HER2 genes in a patient's breast cancer cells using a fluorescent dye so the HER2 genes can be visualized and counted with a special microscope.
Study Recommends HER2 Testing for All Invasive Breast Cancer
The American Society of Clinical Oncology and the College of American Pathologists panel members involved in the JCO study recommend that HER2 status should be tested for all invasive breast cancer. The panel also is calling for validation of laboratory tests, use of standardized operating procedures and compliance with new monitored testing criteria.
Komen Foundation Perspective
The Susan G. Komen Breast Cancer Foundation applauds the development of this guideline. This review acknowledges the current problems with HER2 testing and offers solutions that include adoption of routine HER2 testing for breast cancer patients.
We agree with the recommendation that all patients with invasive breast cancer be tested for HER2. We support the need for validation, standardization and compliance.
The medical profession has a responsibility to ensure that uniform quality standards are in place. Adoption of these guidelines will be critical to obtaining accurate diagnoses, providing patients a better chance for the best possible outcome from their treatment choices.
