HERmark Breast Cancer Assay precisely quantifies HER2 total protein and HER2 homodimer levels in Formalin Fixed Parrafin Embedded Tissue. The preliminary results of one study presented at the most recent ASCO Annual Meeting (Leitzel et al, Abstract 1002), indicate that this assay was a better predictor than FISH testing of response to trastuzumab.
The preliminary results also indicated discordance between assessments of HER2 status as measured by the HERmark assay and FISH. Specifically, 14% of FISH-negative patients were determined to be HER2 high expressors by HERmark, and 13% of FISH-positive patients were determined to be HER2 low expressors. Determination of HER-2/neu status has thus taken on great importance in the routine work-up of breast cancer in the pathology laboratory:over-expression of the protein product of HER-2/neu gene is usually a direct consequence of gene amplification, in which multiple copies of the gene appear throughout the genome. The two most widely used technologies are immunohistochemistry (IHC) and FISH, because these two techniques are ideal for use on paraffin embedded tissue, including archival material.FISH is considered the gold standard for HER2 assessment and correlates best with outcome and response to traztuzamab treatment.While FISH detects gene amplification, IN+HC detects gene product overexpression.In relation to IHC methods of HER assessments, FISH is usually considered superior. It would stand to reason that HERmark is superior to IHC.
However, no direct comparisons have been carried out. ASCO/CAP guidelines recommend that HER2 status be determined for all invasive breast cancer patients. These guidelines caution that current HER2 testing methods (central IHC and FISH) may be inaccurate in up to 20% of cases. HERmark Breast Cancer Assay precisely quantifies HER2 total protein and HER2 homodimer levels in FFPE. HERmark reclassified up to 25% of samples from a cohort of the FinHer Adjuvant Breast Cancer Study. It is not known whether there is a benefit to test by two modalities or not and HERmark is only one a panoply of next generation of HER tests that are available or coming the the market.
Antonio C. Wolff, M. Elizabeth Hale Hammond, Kimberly H. Allison, Brittany E. Harvey, Pamela B. Mangu, John M.S. Bartlett, Michael Bilous, Ian O. Ellis, Patrick Fitzgibbons, Wedad Hanna, Robert B. Jenkins, Michael F. Press, Patricia A. Spears, Gail H. Vance, Giuseppe Viale, Lisa M. McShane, and Mitchell Dowsett, Epidermal Growth Factor Receptor 2 Testing in Breast Cancer: American Society of Clinical Oncology/College of American Pathologists Clinical Practice Guideline Focused Update. Journal of Clinical Oncology 2018 36:20, 2105-2122
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