Evaluation of analytical accuracy of HER2 status in patients with breast cancer

Abstract

Human epidermal growth factor receptor 2 (HER2) gene status and overexpression, occurring in~13.6% of primary breast cancers, is essential for identifying patients likely to benefit from biological treatment. In this method of evaluation study, we tested and compared the HER2 gene-protein assay (GPA) with routine HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). The GPA was evaluated using 67 formalin-fixed paraffin-embedded (FFPE) HER2 equivoval IHC (2+) breast cancer tissue samples. Overall, agreement between GPA silver in situ hybridization (SISH) and FISH was 91.9% (57/62). Regression analysis revealed slightly higher, but non-significant difference in HER2/chromosome enumeration probe 17 (CEP17) ratio for GPA as compared to FISH (p = 0.074). Intraclass correlation coefficients (ICCs) of 0.94 and Spearman´s rank correlation coefficients of 0.93 (p < 0.0001) for FISH and GPA SISH suggested strong inter-observer association for methods with one observer counting on average 0.23 significant higher for GPA SISH (p = 0.014). Intra-observer IHC method reproducibility was 52.6% (j = 0.3122, p = 0.004) and 79.7% (j = 0.6428, p = 0.9197), suggesting fair significant and substantial non-significant difference between tests for reviewers. Inter-observer reproducibility for IHC methods was 53%. While inter-observer reproducibility for experienced IHC interpretation suggested significant differences (j = 0.3636, p = 0.0332), unexperienced interpretation of IHC GPA suggested fair non-significant difference between reviewers (j = 0.3101, p = 0.0747). Using FISH as reference, the diagnostic indices for GPA SISH were as follows: sensitivity 100%, specificity 95% and accuracy 92%. Inaccuracy between tests was in 80% of cases due to ISH categorization as equivocal by one of the methods. IHC results highlight that it may be beneficial with a method for simultaneously visualization of HER2 gene and protein status.

[Retracted] Application of Fluorescence In Situ Hybridization Assisted by Fluorescence Microscope in Detection of Her2 Gene in Breast Cancer Patients

“…At present, Immunohistochemistry (IHC) and fluorescence in situ hybridization (Fluorescence in situ) are the main techniques recommended by the US Food and Drug Administration for Her2 gene detection. Many studies have confirmed that there are two kinds of hybridization and FISH [6][7][8]. Although the two detection methods have good consistency in the detection of Her2 gene status, for PA-TIENTS with IHC (2+), further detection by FISH is more beneficial to obtain more accurate gene status information.…”

Male Accessory Breast Cancer Successfully Treated With Single-Agent Trastuzumab: A Case Report

“…According to the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) criteria, if the HER-2/CEP17 ratio is ≥2.0 or the HER-2 gene copy number is ≥6, the test result is considered HER-2 positive. (Jensen et al, 2020). As an effective method, combined chemotherapy with trastuzumab has become a standard treatment for HER-2 overexpressing breast cancer.…”

Pathological identification of HER2-low breast cancer: Tips, tricks, and troubleshooting for the optimal test

“…On the other hand, in the post-analytical phase, inter-observer variability can occur due to the lack of consistent epithelial internal positive control for HER2 in non-neoplastic breast tissue ( Sajjadi et al, 2022 ; Zhang et al, 2022 ). The subjective mode of HER2 assessment and HER2 intratumoral heterogeneity in HER2-low breast cancer are other barriers with great influence on HER2-low assessment ( Bianchi et al, 2015 ; Jensen et al, 2020 ; Zhang et al, 2020 ). To determine the suitability of the current standard HER2 IHC assays for identifying patients with HER2-low breast cancers, a concordance survey of 18 pathologists reading 170 breast cancer biopsies was carried out ( Fernandez et al, 2022 ).…”