219 Comparison of Two FDA-Approved Her2 Immunohistochemical Assays for Breast Carcinoma: HercepTest and Pathway Her2 (4B5). (11th January 2018)

• Record Type: Journal Article
• Authors: Jabbar, Seema; Lucas, Elena; Fang, Yisheng; Molberg, Kyle; Blacketer, Sara; Sahoo, Sunati
• Is Part Of: American journal of clinical pathology. Volume 149(2018)Supplement 1
• Page Start: S93
• Page End: S94
• Publication Date: 2018-01-11
• Subjects: Diagnosis, Laboratory -- Periodicals; Pathology -- Periodicals; 616.07
• DOI: 10.1093/ajcp/aqx123.218
• Languages: English
• ISSNs: 0002-9173

Abstract

Abstract: Background: A false-negative or false-positive Her2 status may lead to inappropriate therapy in breast cancer patients. The criteria for Her2 interpretations by immunohistochemistry (IHC) and by in situ hybridization (ISH) were revised in 2013 by the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP). The revised guidelines recommend confirming equivocal Her2 IHC results by an alternate method. A few instances of false-positive Her2 results by IHC in our laboratory prompted us to compare the performance of two HER2 antibodies approved by the US Food and Drug Administration. Design: A total of 95 equivocal (72) and positive (23) cases by HercepTest (Dako) were tested with Pathway Her2/4B5 (Ventana) and Pathvysion Her2 fluorescence ISH (FISH; Abbott). All interpretations for IHC and FISH were done according to the 2013 ASCO/CAP guidelines. Three pathologists scored the Her2 IHC independently. Consensus opinion was used to resolve cases in which the pathologists disagreed on the IHC score. Results: Of the 95 cases tested with 4B5, 55% were negative, 26% equivocal, and 19% positive. Fifty-two (72%) of the equivocal cases with HercepTest were interpreted as negative with 4B5. Of the 72 equivocal HercepTest results, 71% (51) were non-amplified, 12% (9) equivocal and 17% (12) amplified by FISH. Of the 25 equivocal results with 4B5, 36% (9) were non-amplified, 20% (5) equivocal and 44% (11) amplified by FISH. Of the 23 positive results with HercepTest, 9% (2) were non-amplified by FISH and one (4%) was equivocal. All of the positive cases by 4B5 were amplified by FISH. Three Her2-negative IHC cases by 4B5 were amplified by FISH (two had monosomy 17 and one polysomy 17). By cost analysis, testing of equivocal IHC cases with FISH amounted to $14, 590 for HercepTest and $5, 066 for 4B5. Conclusions: Even with the small sample tested, Pathway Her2 had a higher concordance with Her2 FISH results than HercepTest. There is a significant cost savings using Pathway Her2 compared to HercepTest.