A Qualitative Study Comparing the Assay Performance Characteristics Between the 2007 and the 2013 American Society for Clinical Oncology and College of American Pathologists HER2 Scoring Methods in Mucinous Epithelial Ovarian Cancer

The remarkable success of trastuzumab and other newly developed anti-HER2 (human epidermal growth factor receptor 2) therapies in breast, gastric, or gastroesophageal junction cancer patients has supported us to investigate the HER2 status and its possible therapeutic implication in mucinous epithelial ovarian cancer (EOC). However, there is currently no standardization of HER2 scoring criteria in mucinous EOC. In this study, we aimed to compare both the assay performance characteristics of the 2007 and the 2013 American Society for Clinical Oncology and College of American Pathologists scoring methods. Forty-nine tissue microarray samples of mucinous EOC from Asian women were analyzed by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) tests using the 2007 and the 2013 criteria, respectively. The overall concordance between IHC and FISH by the 2007 criteria was 97.92 % (kappa = 0.921), and that by the 2013 criteria was 100% (kappa = 1.000). The percentage of Her2 FISH-amplified cases showed an increasing trend significantly through their corresponding HER2 IHC ordinals by the 2007 and the 2013 criteria, respectively (P < 0.001, P < 0.001). After excluding equivocal cases, the specificity (100%) and positive predictive value (100%) were unchanged under either the 2007 or the 2013 criteria. The sensitivity (100%), negative predictive value (NPV) (100%), and accuracy (100%) of HER2 IHC were higher under the 2013 criteria than those (sensitivity 87.5%, NPV 97.6%, and accuracy 97.9%) under the 2007 criteria. Of the total 49 cases, the number (n = 4) of HER2 IHC equivocal results under the 2013 criteria was 4-fold higher than that (n = 1) under the 2007 criteria (8.16% vs 2.04%). Conclusively, if first tested by IHC, the 2013 criteria caused more equivocal HER2 IHC cases to be referred to Her2 FISH testing than the 2007 criteria. That decreased the false-negative rate of HER2 status and increased the detection rates of HER2 positivity in mucinous EOC.