Current Perspectives on HER2 Testing: A Review of National Testing Guidelines

Abstract

Knowledge of HER2 status is a prerequisite when considering a patient's eligibility for Herceptin (trastuzumab) therapy. Accurate assessment of HER2 status is essential to ensure that all patients who may benefit from Herceptin are correctly identified. There are several assays available to determine HER2 status: the most common in routine clinical practice are immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Various factors can affect the results achieved with these assays, including the assay antibody/probe, the methodology and the experience of personnel. Many countries have implemented national testing guidelines in an attempt to standardize testing procedures and make results more accurate. These guidelines vary in the level of detail and the number of recommendations. This review looks at areas of consensus between the different national testing guidelines and highlights where errors may arise during the testing procedure. The key point underlined by this review is that whatever method is used to test for HER2 status, the technology must be validated first, and there must be regular internal and external quality control and quality assurance procedures. Progress in molecular biology has resulted in the identification and greater understanding of molecular markers that may have prognostic and predictive value for breast cancer patients. The human epidermal growth factor receptor-2 (HER2/neu/cerbB-2) is one of the best characterized of such markers. The subset of patients with breast cancer demonstrating a HER2-positive status has aggressive tumors and a poor prognosis (1-3). There is mounting evidence that HER2 status may predict response to chemotherapy and hormonal therapy, although conclusive data are needed (4, 5). Most important, demonstration of high HER2 receptor overexpression or HER2 gene amplification is essential for treatment with the anti-HER2 monoclonal antibody therapy Herceptin, which has significant clinical benefits in patients with metastatic breast cancer (6 -8). Clinical studies have also shown that the level of HER2 overexpression correlates with clinical benefit. Patients whose tumors have high HER2 receptor overexpression and/or amplification of the HER2 gene benefit most from Herceptin (7, 9 -11). For these reasons, testing for HER2 status is important for the management of patients with breast cancer, and accurately assessing HER2 status is essential in deciding which patients will benefit from Herceptin therapy. Currently, no single assay is globally accepted as the gold standard for HER2 testing. Factors that can lead to inaccuracies in HER2 testing results include preparation, fixation, and storage of the tissue sec-

A modified Trastuzumab antibody for the immunohistochemical detection of HER-2 overexpression in breast cancer

“…However, in the series of patients treated with Trastuzumab, we noted suboptimal (i.e., cytoplasmic and background) BiotHER staining in seven cases (three tumours were nonresponsive and four responded to Trastuzumab treatment) received from external laboratories. These data confirm the need for optimal tissue processing as a prerequisite for reliable HER-2 IHC staining (Bilous et al, 2003).…”

“…In addition, 4D5 is not commercially available. HER-2 diagnostic testing recommendations (Bilous et al, 2003), proposed by different nations, do not consider 4D5 mAb as an IHC marker and, to our knowledge, no work has been published on the correlation between 4D5 immunostaining and HER-2 gene amplification by FISH analysis in tissue specimens. We decided upon biotinylation of Trastuzumab to avoid incubation with a secondary anti-human IgG, which could create problems of background staining.…”

Comparison of automated silver enhanced in situ hybridization and fluorescence in situ hybridization for evaluation of epidermal growth factor receptor status in human glioblastomas

“…Fluorescence in situ hybridization is globally accepted and used as a standard method to determine HER2 status in breast cancer. 8,9 Disadvantages of fluorescence in situ hybridization testing are an expensive fluorescent microscope, extensive user training and rapid loss of gene signals at room temperature, thereby hindering convenient slide storage. Currently, fluorescence in situ hybridization is the gold standard.…”

MET overexpression assessed by new interpretation method predicts gene amplification and poor survival in advanced gastric carcinomas

“…28 To better characterize MET-positive gastric cancers and develop a sensitive predictor of benefit from METMab, we conducted immunohistochemistry with the same monoclonal primary antibody used for recent MET clinical trials. 25,27 Materials and methods…”