Standardization of HER2 testing: results of an international proficiency-testing ring study

Immunohistochemistry and fluorescence in situ hybridization assessment of HER2 in clinical trials of adjuvant therapy for breast cancer (NCCTG N9831, BCIRG 006, and BCIRG 005)

A comprehensive, blinded, pathology evaluation of HER2 testing in HER2-positive/negative breast cancers was performed among three central laboratories. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) analyses were performed on 389 tumor blocks from three large adjuvant trials: N9831, BCIRG-006, and BCIRG-005. In 123 cases, multiple blocks were examined. HER2 status was defined according to FDA-approved guidelines and was independently re-assessed at each site. Discordant cases were adjudicated at an on-site, face-to-face meeting. Results across three independent pathologists were concordant by IHC in 351/381 (92 %) and FISH in 343/373 (92 %) blocks. Upon adjudication, consensus was reached on 16/30 and 18/30 of discordant IHC and FISH cases, respectively, resulting in overall concordance rates of 96 and 97 %. Among 155 HER2-negative blocks, HER2 status was confirmed in 153 (99 %). In the subset of 102 HER2-positive patients from N9831/BCIRG-006, primary blocks from discordant cases were selected, especially those with discordant test between local and central laboratories. HER2 status was confirmed in 73 (72 %) of these cases. Among 118 and 113 cases with IHC and FISH results and >1 block evaluable, block-to-block variability/heterogeneity in HER2 results was seen in 10 and 5 %, respectively. IHC−/FISH− was confirmed for 57/59 (97 %) primary blocks from N9831 (locally positive, but centrally negative); however, 5/22 (23 %) secondary blocks showed HER2 positivity. Among 53 N9831 patients with HER2-normal disease adjudicated as IHC−/FISH—(although locally positive), there was a non-statistically significant improvement in disease-free survival with concurrent trastuzumab compared to chemotherapy alone (adjusted hazard ratio 0.34; 95 % CI, 0.11–1.05; p = 0.06). There were similar agreements for IHC and FISH among pathologists (92 % each). Agreement was improved at adjudication (96 %). HER2 tumor heterogeneity appears to partially explain discordant results in cases initially tested as positive and subsequently called negative.

Comparison of dual-color dual-hapten brightfield in situ hybridization (DDISH) and fluorescence in situ hybridization in breast cancer HER2 assessment

The most optimal method for assessing HER2 status is still subject to controversy as far as the type of assay used, the optimal method to perform, and the costs of each assay are concerned. The current study was done as a validation study prior to setting up a clinical HER2 testing service using the new commercial dual-color dual-hapten brightfield in situ hybridization (DDISH), but it was felt that our experience may be of interest to other laboratories considering setting up HER2 diagnostic facilities. One hundred and five patients diagnosed with invasive breast cancer were selected. PathVysion FISH and DDISH assays were carried out. Concordance correlation coefficients showed near perfect agreement in average HER2 and centromere-specific signal counts per cell and in HER2/CEN17 ratios between the PathVysion and the DDISH assays, and also the Kappa measure showed near perfect agreement between the two assays (Kappa=0.8712, P<0.0001). Statistical analysis confirmed that the two assays are comparable in terms of detection of HER2 gene amplification and suggests its utilization in routine HER2 diagnostics.

HER2 and ESR1 mRNA expression levels and response to neoadjuvant trastuzumab plus chemotherapy in patients with primary breast cancer

INTRODUCTION

Recent data suggest that benefit from trastuzumab and chemotherapy might be related to expression of HER2 and estrogen receptor (ESR1). Therefore, we investigated HER2 and ESR1 mRNA levels in core biopsies of HER2-positive breast carcinomas from patients treated within the neoadjuvant GeparQuattro trial.

METHODS

HER2 levels were centrally analyzed by immunohistochemistry (IHC), silver in situ hybridization (SISH) and qRT-PCR in 217 pretherapeutic formalin-fixed, paraffin-embedded (FFPE) core biopsies. All tumors had been HER2-positive by local pathology and had been treated with neoadjuvant trastuzumab/ chemotherapy in GeparQuattro.

RESULTS

Only 73% of the tumors (158 of 217) were centrally HER2-positive (cHER2-positive) by IHC/SISH, with cHER2-positive tumors showing a significantly higher pCR rate (46.8% vs. 20.3%, P <0.0005). HER2 status by qRT-PCR showed a concordance of 88.5% with the central IHC/SISH status, with a low pCR rate in those tumors that were HER2-negative by mRNA analysis (21.1% vs. 49.6%, P <0.0005). The level of HER2 mRNA expression was linked to response rate in ESR1-positive tumors, but not in ESR1-negative tumors. HER2 mRNA expression was significantly associated with pCR in the HER2-positive/ESR1-positive tumors (P = 0.004), but not in HER2-positive/ESR1-negative tumors.

CONCLUSIONS

Only patients with cHER2-positive tumors - irrespective of the method used - have an increased pCR rate with trastuzumab plus chemotherapy. In patients with cHER2-negative tumors the pCR rate is comparable to the pCR rate in the non-trastuzumab treated HER-negative population. Response to trastuzumab is correlated to HER2 mRNA levels only in ESR1-positive tumors. This study adds further evidence to the different biology of both subsets within the HER2-positive group.

Quantitative analysis of diagnostic guidelines for HER2-status assessment

Human epidermal growth factor receptor 2 (HER2, alias ERBB2)-targeted therapy in breast and gastric cancers depends on the reliable assessment of HER2 protein expression and (in equivocal cases) the quantitative evaluation of HER2 gene amplification. Typically, HER2 and centromere 17 gene copy numbers are evaluated using in situ hybridization (ISH) to calculate ratios for which cutoff values dividing nonamplified and amplified cases have been proposed. Although several studies have investigated how laboratory procedures affect diagnostics, a rigorous quantitative assessment of the diagnostic guidelines for data analysis is still missing. Here, we analyze the dependence of the diagnosed HER2/chromosome 17 ratios on i) sample size (evaluated cells), ii) gene/chromosome signal distributions, and iii) the approach used for quotient calculation using Monte Carlo simulations. Our data show that the current recommendation may lead to statistical HER2/CHR17 ratio variations of up to 0.94 and may therefore lead to incorrect HER2 status diagnoses, given the ratio threshold of 2.0 defined by the Food and Drug Administration. Moreover, borderline cases may receive different amplification diagnoses, depending on the ratio calculation approach: Brightfield-silver ISH with aggregated signal counts may underestimate the HER2/CHR17 ratio compared with two-color fluorescence ISH. Our results provide a basis for quantitative rationales behind HER2 diagnostic guidelines that call for increased numbers of evaluated cells and emphasize the importance of well-designed data analysis methods in diagnostic pathology, especially for predictive clinical application.

Determining sensitivity and specificity of HER2 testing in breast cancer using a tissue micro-array approach

Introduction

Overexpression of the human epidermal growth factor receptor 2 (HER2) as a result of HER2 gene amplification is associated with a relatively poor prognosis in breast cancer and is predictive of HER2-targeting therapy response. False-positive rates of up to 20% for HER2 testing have been described. HER2-testing laboratories are therefore encouraged to participate in external quality control schemes in order to improve HER2-testing standardization.

Methods

This study investigated the feasibility of retesting large numbers of invasive breast cancers for HER2 status on tissue micro-array (TMA) as part of a quality control scheme. For this assessment different HER2 testing methods were used including HER2 detecting antibodies SP3, 4B5, Herceptest and mono color silver in situ hybridization (SISH) and dual color SISH. Final HER2 status for each tumor on the TMA was compared to the local testing result for the same tumor. Discordances between these two results were investigated further by staining whole tumor sections.

Results

For this study, 1,210 invasive breast carcinomas of patients treated in six hospitals between 2006 and 2008 were evaluated. Results from the three immunohistochemistry (IHC) and two in situ hybridization (ISH) assays performed on the TMAs were compared. The final HER2 status on TMA was determined with SP3, 4B5 and mono color SISH. Concordance between local HER2 test results and TMA retesting was 98.0%. Discordant results between local and TMA retesting were found in 20 tumors (2.0%). False positive HER2 IHC results were identified in 13 (1.3%) tumors; false negative IHC results in seven (0.7%) tumors.

Conclusions

Retesting large volumes of HER2 classified breast carcinomas was found to be feasible and can be reliably performed by staining TMAs with SP3, 4B5 and mono color SISH in combination with full-sized slides for discordant cases. The frequency of false-positive results was lower than previously reported in the literature. This method is now offered to other HER2-testing laboratories.

'Genetic heterogeneity' in HER2/neu testing by fluorescence in situ hybridization: a study of 2,522 cases

Amplification for the ERBB2 oncogene encoding the HER2/neu protein (HER2) is of predictive and prognostic importance in breast carcinoma. Fluorescence in situ hybridization (FISH) is a widely accepted method for determining HER2 amplification status. A HER2-amplified tumor is defined as having a ratio of HER2 signals to chromosome 17 centromeric probe signals (HER2/CEP17 ratio) exceeding 2.2. However, the presence of scattered cells demonstrating HER2 amplification is of unclear significance. A 2009 panel guideline defined a tumor with 'genetic heterogeneity' as having at least 5% but fewer than 50% of (non-clustered) tumor nuclei with a ratio >2.2. The study objective was to examine the statistical distribution of breast tumors tested by FISH for HER2 amplification, after implementation of this 2009 guideline. We identified 2522 consecutive breast carcinoma cases (2009-2011) tested for HER2 amplification. All cases were tested by FISH using a standard clinical protocol, adhering to established guidelines. For each case, data on cell counts were retrieved electronically. Each tumor was compared with a theoretical normal distribution by quantile-quantile analysis. Of 2522 FISH tests for HER2, 1900 (75%) were non-amplified, 394 (16%) were amplified, and 228 (9%) were HER2-equivocal. A total of 666 (26%) had 'genetic heterogeneity.' Among these 'genetically heterogeneous' cases, the ratio was non-amplified in 430 (64.5%), amplified in 24 (4%), and equivocal in 212 (31.5%). The amplified subpopulation in 'genetically heterogeneous' tumors was larger if the overall ratio was close to 2.2. However, the percentage of nuclei >2.2 in a 'genetically heterogeneous' tumor was not informative of the underlying tumor-cell distribution. We conclude that the proportion of HER2-amplified nuclei within a tumor does not contribute information independent of the actual HER2/CEP17 ratio. Reassessment of the definition of 'genetic heterogeneity' in HER2 testing is warranted.

HER2 testing in gastric cancer: a practical approach

Trastuzumab in combination with capecitabine or 5-fluorouracil and cisplatin is approved by the European Medicines Agency for the treatment of patients with human epidermal growth factor receptor 2 (HER2)-positive (immunohistochemistry 3+ or immunohistochemistry 2+/fluorescence in situ hybridization-positive or immunohistochemistry 2+/silver in situ hybridization-positive) metastatic adenocarcinoma of the stomach or gastro-esophageal junction. Approvals are underway in other countries, with recent approvals granted in the United States and Japan. Experience and data from trastuzumab use in breast cancer have highlighted the importance of quality HER2 testing and scoring to ensure accurate identification of patients eligible for treatment. HER2 testing in gastric cancer differs from testing in breast cancer due to inherent differences in tumor biology; gastric cancer more frequently shows HER2 heterogeneity (focal staining) and incomplete membrane staining. Consequently, gastric cancer-specific HER2 testing protocols have been developed and standardized and it is imperative that these recommendations be adhered to. Given the predictive value of HER2 protein levels with response in the trastuzumab for GAstric cancer study (ToGA), immunohistochemistry should be the initial testing methodology and fluorescence in situ hybridization or silver in situ hybridization should be used to retest immunohistochemistry 2+ samples. Wherever possible, bright-field methodologies should be used as these are considered to be superior to fluorescent methodologies at identifying heterogeneous staining. Specific training is required before embarking on HER2 testing in gastric cancer, irrespective of the experience of HER2 testing in breast cancer. This paper provides the most up-to-date practical guidance on HER2 testing and scoring in patients with gastric and gastro-esophageal junction cancer, as agreed by a panel of expert pathologists with extensive experience of HER2 testing particularly reflecting the European Medicines Agency-approved indication. It is anticipated that these recommendations should ensure accurate and consistent HER2 testing, which will allow appropriate selection of patients eligible for treatment with trastuzumab.

Efficacy of primed in situ labelling in determination of HER-2 gene amplification and CEN-17 status in breast cancer tissue

Considerable attention has been given to the accuracy of HER-2 testing and the correlation between the results of different testing methods. This interest reflects the growing importance of HER-2 status in the management of patients with breast cancer. In this study the detection of HER-2 gene and centromere 17 status was evaluated using dual-colour primed in situ labelling (PRINS) in comparison with fluorescence in situ hybridization (FISH). These two methods were evaluated on a series of 27 formalin fixed paraffin embedded breast carcinoma tumours, previously tested for protein overexpression by HercepTest (grouped into Hercep 1+/0, 2+ and 3+). HER-2 gene amplification (ratio ≥ 2.2) by PRINS was found in 3:3, 6:21 and 0:3 in IHC 3+, 2+ and 1+/0 cases, respectively. Comparing FISH and IHC (immunohistochemistry), showed the same results as for PRINS and IHC. Chromosome 17 aneusomy was found in 10 of 21 IHC 2+ cases (47.6%), of which 1 (10%) showed hypodisomy (chromosome 17 copy number per cell ≤ 1.75), 7 (70%) showed low polysomy (chromosome 17 copy number per cell=2.26 - 3.75) and 2 (20%) showed high polysomy (chromosome 17 copy number per cell ≥ 3.76). The overall concordance of detection of HER-2 gene amplification by FISH and PRINS was 100% (27:27). Furthermore, both the level of HER-2 amplification and copy number of CEN17 analysis results correlated well between the two methods. In conclusion, PRINS is a reliable, reproducible technique and in our opinion can be used as an additional test to determine HER-2 status in breast tumours.

Effectiveness of silver-enhanced in situ hybridization for evaluating HER2 gene status in invasive breast carcinoma: a comparative study

BACKGROUND AND AIMS

HER2 gene amplification occurs in breast cancers and has implications for treatment and prognosis. Recently, a new direct evaluation technique, silver enhanced in situ hybridization (SISH) was developed for evaluating HER2 gene status. This study was performed to evaluate the SISH technique for clinical use by comparing it to that of fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC).

METHODS

We studied 543 cases of excised breast specimens diagnosed as invasive ductal carcinoma by IHC, FISH, and SISH using a tissue microarray. IHC, FISH, and SISH results were interpreted according to the American Society of Clinical Oncology/College of American Pathologists guidelines. A total of seven English studies that reported the concordance rates of SISH and BDISH compared to FISH published before July 2011 were retrieved.

RESULTS

The consensus concordance rate between SISH and FISH was 96.69% (kappa value = 0.9175). The pooled sensitivity was 0.94 [95% confidence interval (CI) = 0.91-0.97], and the pooled specificity was 0.98 (95% CI = 0.96-099) in a meta-analysis of the retrieved studies and this study. Area under the receiver operating characteristics curve was 0.9906.

CONCLUSIONS

SISH technique is an effective modality and is comparable with FISH for evaluating HER2 gene amplification in patients with breast carcinoma.

Prognostic value of TOP2A gene amplification and chromosome 17 polysomy in early breast cancer

The aim of this study was to analyze the occurrence of TOP2A gene amplification and chromosome 17 polysomy in patients with early breast cancer and to correlate the status of these alterations with the prognostic significance expressed as patients' clinical features and survival. Such concurrent analyses of TOP2A gene status and chromosome 17 polysomy have not been performed before. Study group included 149 consecutive stage I-III patients administered standard multimodality treatment. TOP2A abnormalities were examined by standard fluorescence in situ hybridization (FISH) and developed by our group quantitative real-time PCR (qPCR). TOP2A amplification and deletion assessed by FISH were found in 23% and 7% of the tumours, respectively, and by qPCR in 31% and 11% of the tumours, respectively. Chromosome 17 polysomy was detected in 40% of the cases. TOP2A amplification (by qPCR) correlated with shorter disease-free survival (p = 0.03) and overall survival (p = 0.047), and the prognostic value of TOP2A was confirmed in the multivariate analysis (HR = 3.22, 95% CI 1.09-9.56, p = 0.03). TOP2A gene amplification, but not chromosome 17 polysomy, carries negative prognostic information in early breast cancer. Given the aforementioned results, qPCR might serve as a prognostic tool in determining the patient's prognosis.

Internal Quality Assurance Program for ERBB2 (HER2) Testing Improves the Selection of Breast Cancer Patients for Treatment with Trastuzumab

International guidelines for ERBB2 (HER2) testing procedures in breast cancer patients highlight the importance of external quality control. In contrast, internal quality assurance programs have been poorly defined, and their clinical significance has not yet been investigated. We developed a quality assurance scheme by performing HER2 FISH on 724 patients randomly selected out of 1996 patients with breast cancer presenting at our institute. We collected samples monthly for tissue microarray analysis and correlated HER2 gene status with IHC scores. The concordance was excellent (κ = 0.92, P < 0.0001). HER2 amplification characterized 25% of score 2+ but also 13% of score 1+, thus expanding the number of patients eligible for trastuzumab. Based on these findings, the FISH test is now recommended at our institution for score 1+ and 2+ patients. Adherence to internal assurance program improves patient selection and may lead to the definition of in-house tailored diagnostic algorithms different from those proposed in international guidelines.

EGFR and KRAS quality assurance schemes in pathology: generating normative data for molecular predictive marker analysis in targeted therapy

INTRODUCTION

The aim of this study was to compare the reproducibility of epidermal growth factor receptor (EGFR) immunohistochemistry (IHC), EGFR gene amplification analysis, and EGFR and KRAS mutation analysis among different laboratories performing routine diagnostic analyses in pathology in The Netherlands, and to generate normative data.

METHODS

In 2008, IHC, in-situ hybridisation (ISH) for EGFR, and mutation analysis for EGFR and KRAS were tested. Tissue microarray sections were distributed for IHC and ISH, and tissue sections and isolated DNA with known mutations were distributed for mutation analysis. In 2009, ISH and mutation analysis were evaluated. False-negative and false-positive results were defined as different from the consensus, and sensitivity and specificity were estimated.

RESULTS

In 2008, eight laboratories participated in the IHC ring study. In only 4/17 cases (23%) a consensus score of ≥75% was reached, indicating that this analysis was not sufficiently reliable to be applied in clinical practice. For EGFR ISH, and EGFR and KRAS mutation analysis, an interpretable result (success rate) was obtained in ≥97% of the cases, with mean sensitivity ≥96% and specificity ≥95%. For small sample proficiency testing, a norm was established defining outlier laboratories with unsatisfactory performance.

CONCLUSIONS

The result of EGFR IHC is not a suitable criterion for reliably selecting patients for anti-EGFR treatment. In contrast, molecular diagnostic methods for EGFR and KRAS mutation detection and EGFR ISH may be reliably performed with high accuracy, allowing treatment decisions for lung cancer.

68Ga-DOTA-affibody molecule for in vivo assessment of HER2/neu expression with PET

PURPOSE

Overexpression of HER2/neu in breast cancer is correlated with a poor prognosis. It may vary between primary tumors and metastatic lesions and change during the treatment. Therefore, there is a need for a new means to assess HER2/neu expression in vivo. In this work, we used (68)Ga-labeled DOTA-Z(HER2:2891)-Affibody to monitor HER2/neu expression in a panel of breast cancer xenografts.

METHODS

DOTA-Z(HER2:2891)-Affibody molecules were labeled with (68)Ga. In vitro binding was characterized by a receptor saturation assay. Biodistribution and PET imaging studies were conducted in athymic nude mice bearing subcutaneous human breast cancer tumors with three different levels of HER2/neu expression. Nonspecific uptake was analyzed using non-HER2-specific Affibody molecules. Signal detected by PET was compared with ex vivo assessment of the tracer uptake and HER2/neu expression.

RESULTS

The (68)Ga-DOTA-Z(HER2:2891)-Affibody probe showed high binding affinity to MDA-MB-361 cells (K (D) = 1.4 ± 0.19 nM). In vivo biodistribution and PET imaging studies demonstrated high radioactivity uptake in HER2/neu-positive tumors. Tracer was eliminated quickly from the blood and normal tissues, resulting in high tumor-to-blood ratios. The highest concentration of radioactivity in normal tissue was seen in the kidneys (227 ± 14%ID/g). High-contrast PET images of HER2/neu-overexpressing tumors were recorded as soon as 1 h after tracer injection. A good correlation was observed between PET imaging, biodistribution estimates of tumor tracer concentration, and the receptor expression.

CONCLUSION

These results suggest that PET imaging using (68)Ga-DOTA-Z(HER2:2891)-Affibody is sensitive enough to detect different levels of HER2/neu expression in vivo.

Molecular assays in breast cancer pathology

Recent advances in understanding the molecular pathology of breast cancer offer significant potential to identify patients who may benefit from adjuvant therapies. To date, few of these advances are utilised in a routine setting. We review molecular assays that are currently in use or are in the advanced stages of development, which may be used as predictive or prognostic biomarkers in breast cancer.The only widely used breast cancer molecular assay is in situ hybridisation (ISH) for human epidermal growth factor receptor 2 (HER2) gene amplification and we highlight key issues with the interpretation of this assay, with particular attention to the difficulties of the equivocal category. New molecular assays such as ISH for the topoisomerase II alpha (TOP2A) gene and for the aberrations in the copy number of the centromeric region of chromosome 17 are readily performed in a standard histopathology laboratory, but to date there are insufficient data to support their routine use. We also review the current data on two commercially available multigene expression assays, Oncotype DX and MammaPrint and discuss their potential use. Overall, while new molecular assays have significant potential to improve patient selection for therapy, well-performed histopathology with reliable interpretation of standard hormone and HER2 assays provides the most important predictive and prognostic information in early breast cancer.

Current technologies for HER2 testing in breast cancer

BACKGROUND

Molecular techniques play an increasingly important role in breast cancer detection and help in the prediction of prognosis and treatment response. HER-2/neu predicts the sensitivity of breast tumors to trastuzumab and lapatinib. Presently there are several ways to assess HER2 status at the protein level (e.g. ELISA), at the RNA level (RT-PCR, microarray) and at the DNA level (fluorescence in situ hybridization, chromogenic in situ hybridization (ISH), silver in situ hybridization or multiplex ligation-dependent probe amplification).

DESIGN

This paper provides an overview of new developments in HER2 testing.

RESULTS

Although these techniques correlate well in comparative studies, discrepancies remain. Each technique has its own (dis)advantages and thus there is no real gold standard. Not surprisingly, there is no consensus at present on which of the protein- or gene-based techniques is superior, on the use of mono- or duo-probe ISH systems, nor on the use of manual or fully-automated staining- and scoring systems.

CONCLUSION

Until large clinical trials clearly point out one strategy as the best predictive one for trastuzumab response, the choice for a testing strategy will probably be based on local preferences which consider both practical and economic issues. Standardization, proper internal and external quality control assessment, laboratory accreditation and automation of tissue processing (autostainers) and interpretation methods (image analysis) will play an increasingly important role in HER2 testing.

Use of standard markers and incorporation of molecular markers into breast cancer therapy: Consensus recommendations from an International Expert Panel

Breast cancer is a heterogeneous disease of different subtypes on the molecular, histopathological, and clinical level. Genomic profiling techniques have led to several prognostic and predictive gene signatures of breast cancer that may further refine outcome prediction, especially in clinically equivocal situations. In particular, the predictive value of today's most important therapeutic targets, ER and HER2, are strongly influenced by the proliferative status of the tumor. Genomic assays are generally performed in a centralized manner, whereas routine pathological evaluation is mostly done on a decentralized basis, making the comparison of these methods difficult. Thus, there remains considerable uncertainty about the use of the new molecular markers in routine clinical decision making and their role in patient selection or stratification for future clinical trials. To address this concern, a group of representatives from breast cancer research groups in the areas of breast pathology, genomic profiling, and clinical trials critically reviewed all available data. Consensus recommendations are made on the practical use of molecular markers in breast cancer management and their incorporation into future clinical trials.

[Update of the GEFPICS' recommendations for HER2 status determination in breast cancers in France]

In Europe, patients who may benefit from an HER2 targeted drug are currently selected by immunohistochemistry (IHC). In situ hybridization (ISH) techniques should be used for complementary assessment of ambiguous 2+ IHC cases and for the calibration of the IHC technique. Eligibility to an HER2 target treatment is defined by an HER2 positive status being IHC test 3+ or 2+ amplified. Reliable detection of HER2 status is essential to the appropriate usage of HER2 targeted drugs because its specificity is limited to tumors overexpressing HER2. It is essential that the IHC evaluation of the HER2 status of a mammary carcinoma is optimized and reliable. This GEFPICS' guidelines look over the different steps of the IHC technique, the controls and, the rules for interpretation. Once acquired, this knowledge must be perpetuated by the observation of rules of good technical practice (internal and external controls, quality assurance programs).

Clinical array-based karyotyping of breast cancer with equivocal HER2 status resolves gene copy number and reveals chromosome 17 complexity

Background

HER2 gene copy status, and concomitant administration of trastuzumab (Herceptin), remains one of the best examples of targeted cancer therapy based on understanding the genomic etiology of disease. However, newly diagnosed breast cancer cases with equivocal HER2 results present a challenge for the oncologist who must make treatment decisions despite the patient's unresolved HER2 status. In some cases both immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are reported as equivocal, whereas in other cases IHC results and FISH are discordant for positive versus negative results. The recent validation of array-based, molecular karyotyping for clinical oncology testing provides an alternative method for determination of HER2 gene copy number status in cases remaining unresolved by traditional methods.

Methods

In the current study, DNA extracted from 20 formalin fixed paraffin embedded (FFPE) tissue samples from newly diagnosed cases of invasive ductal carcinoma referred to our laboratory with unresolved HER2 status, were analyzed using a clinically validated genomic array containing 127 probes covering the HER2 amplicon, the pericentromeric regions, and both chromosome 17 arms.

Results

Array-based comparative genomic hybridization (array CGH) analysis of chromosome 17 resolved HER2 gene status in [20/20] (100%) of cases and revealed additional chromosome 17 copy number changes in [18/20] (90%) of cases. Array CGH analysis also revealed two false positives and one false negative by FISH due to "ratio skewing" caused by chromosomal gains and losses in the centromeric region. All cases with complex rearrangements of chromosome 17 showed genome-wide chromosomal instability.

Conclusions

These results illustrate the analytical power of array-based genomic analysis as a clinical laboratory technique for resolution of HER2 status in breast cancer cases with equivocal results. The frequency of complex chromosome 17 abnormalities in these cases suggests that the two probe FISH interphase analysis is inadequate and results interpreted using the HER2/CEP17 ratio should be reported "with caution" when the presence of centromeric amplification or monosomy is suspected by FISH signal gains or losses. The presence of these pericentromeric copy number changes may result in artificial skewing of the HER2/CEP17 ratio towards false negative or false positive results in breast cancer with chromosome 17 complexity. Full genomic analysis should be considered in all cases with complex chromosome 17 aneusomy as these cases are likely to have genome-wide instability, amplifications, and a poor prognosis.

Antibody validation

Antibodies are among the most frequently used tools in basic science research and in clinical assays, but there are no universally accepted guidelines or standardized methods for determining the validity of these reagents. Furthermore, for commercially available antibodies, it is clear that what is on the label does not necessarily correspond to what is in the tube. To validate an antibody, it must be shown to be specific, selective, and reproducible in the context for which it is to be used. In this review, we highlight the common pitfalls when working with antibodies, common practices for validating antibodies, and levels of commercial antibody validation for seven vendors. Finally, we share our algorithm for antibody validation for immunohistochemistry and quantitative immunofluorescence.

Analytical Validation of a Highly Quantitative, Sensitive, Accurate, and Reproducible Assay (HERmark) for the Measurement of HER2 Total Protein and HER2 Homodimers in FFPE Breast Cancer Tumor Specimens

We report here the results of the analytical validation of assays that measure HER2 total protein (H2T) and HER2 homodimer (H2D) expression in Formalin Fixed Paraffin Embedded (FFPE) breast cancer tumors as well as cell line controls. The assays are based on the VeraTag technology platform and are commercially available through a central CAP-accredited clinical reference laboratory. The accuracy of H2T measurements spans a broad dynamic range (2-3 logs) as evaluated by comparison with cross-validating technologies. The measurement of H2T expression demonstrates a sensitivity that is approximately 7–10 times greater than conventional immunohistochemistry (IHC) (HercepTest). The HERmark assay is a quantitative assay that sensitively and reproducibly measures continuous H2T and H2D protein expression levels and therefore may have the potential to stratify patients more accurately with respect to response to HER2-targeted therapies than current methods which rely on semiquantitative protein measurements (IHC) or on indirect assessments of gene amplification (FISH).

Image analysis as an adjunct to manual HER-2 immunohistochemical review: a diagnostic tool to standardize interpretation

Dobson L, Conway C, Hanley A, Johnson A, Costello S, O’Grady A, Connolly Y, Magee H, O’Shea D, Jeffers M & Kay E (2010) Histopathology57, 27–38 Image analysis as an adjunct to manual HER-2 immunohistochemical review: a diagnostic tool to standardize interpretation

TOPOIIalpha and HER-2/neu overexpression/amplification in Barrett's oesophagus, dysplasia and adenocarcinoma

Rossi E, Villanacci V, Bassotti G, Donato F, Festa A, Cengia G, Grisanti S & Cestari R (2010) Histopathology57, 81–89 TOPOIIα and HER-2/neu overexpression/amplification in Barrett’s oesophagus, dysplasia and adenocarcinoma

Reproducibility of human epidermal growth factor receptor 2 analysis in primary breast cancer: a national survey performed at pathology departments in Sweden

BACKGROUND

HER2 is a treatment predictive factor for the effect of trastuzumab and associated with poor prognosis in breast cancer. The analysis of HER2 must be performed with good quality, with regard to both the immunohistochemical (IHC) and in situ hybridization (ISH) analysis.

MATERIAL AND METHODS

A tissue microarray (TMA) including 11 breast cancer samples was sent twice (once in 2005 and again in 2006) to 24 pathology departments in Sweden. A questionnaire was also sent to the departments in 2006.

RESULTS

With IHC, all departments reported the same results (0/1+ vs. 2+ vs. 3 + ) for three (2005) and six samples (2006). The mean kappa-value increased from 0.67 to 0.77, indicating a good reproducibility at both occasions. With fluorescence-ISH (FISH), the 11 departments using this technique reported the same results (amplified vs. normal) for nine (2005) and ten samples (2006). The mean kappa-value showed very good reproducibility both 2005 and 2006 (0.92 and 0.96, respectively). Based on the answers from the participating departments, the questionnaire revealed that 31% of primary breast cancer diagnosed in 2006 (n = 5 043) were 2 + /3+. FISH analysis of 2+ confirmed 12% of the samples to be amplified. The corresponding figure for 3 + was 90%. In total, 14.3% of the samples were HER2 positive (2+ and amplified, or 3 + ).

DISCUSSION

The results obtained in this study indicate that the reproducibility for HER2 analysis is good (IHC) and very good (FISH) between the pathology departments in Sweden using TMA-based tumor samples. In 2006, 14.3% of invasive breast cancers were HER2 positive.

Epidermal growth factor receptor protein expression and gene amplification in normal, hyperplastic, and cancerous glottic tissue: immunohistochemical and fluorescent in situ hybridization study on tissue microarrays

AIM

To evaluate the importance of epidermal growth factor receptor (EGFR) protein overexpression and gene amplification in carcinogenesis of glottic cancer.

METHOD

In order to evaluate EGFR expression at protein and gene level, immunohistochemical (IHC) analysis and fluorescent in situ hybridization (FISH) were performed on tissue microarrays of laryngeal tissue (145 samples) -- 38 samples of normal mucosa, 46 samples of hyperplastic lesions, and 61 samples of cancerous lesions.

RESULTS

Membranous (mEGFR) and cytoplasmic (cEGFR) EGFR expression was significantly different between the analyzed groups. The differences were most striking in the suprabasal-transforming zone. IHC evaluation showed that high and low mEGFR staining contributed to the differentiation of dysplastic lesions, simple hyperplasia, and cancerous tissue, as well as between different degrees of atypia in hyperplastic lesions (P<0.050). EGFR gene amplification was not found in simple and abnormal hyperplastic lesions, but it was confirmed in 2/21 atypical hyperplasias, indicating that gene amplification can facilitate identification of malignant potential in hyperplastic lesions. In cancerous tissue, EGFR gene amplification was found in 8/50 samples. EGFR gene amplification was found in preinvasive cancer in one patient. In invasive carcinomas, gene amplification was not associated with stage or grade. Carcinomas with gene amplification showed significantly higher cEGFR expression (basal layer P=0.003; suprabasal layer P=0.002).

CONCLUSIONS

This study confirmed an increase in EGFR protein expression and gene amplification with the increase in biological aggressiveness of glottic lesions. A correlation between EGFR gene amplification and protein expression was established. Gene amplification proved to be an early event in glottic carcinogenesis, indicating its importance for glottic cancer prevention, early detection, and protocol selection.

Evaluation of HER2 in breast cancer: reality and expectations

BACKGROUND

The introduction of drugs, whose mechanisms of action are directed against specific molecules involved in cancer initiation and/or progression, has changed the daily workup of breast cancer patients. At present, HER2 expression and/or amplification should be evaluated in every primary invasive breast cancer either at the time of diagnosis or at the time of recurrence, mostly to guide selection of trastuzumab in the adjuvant and/or metastatic setting. The adequate selection of patients is an essential step for indication of anti-HER2 therapy.

OBJECTIVE

This review focuses on the state of the art for HER2 evaluation in breast cancer, as well as expectations regarding future molecular assays based on mechanisms of resistance to HER2-driven therapy.

METHODS

Data were obtained by searching the PubMed database, including the terms 'HER2', 'in situ hybridisation', 'immunohistochemistry', 'trastuzumab', 'breast cancer', 'therapy', 'resistance' and 'tyrosine-kinase inhibitors', with a preference for updated publications.

CONCLUSION

Pathologists have a central role in the selection of patients who will benefit from anti-HER-based therapies, with a responsibility to obtain the most reliable results for immunohistochemistry and in situ hybridisation techniques. Pre-analytical variables, such as type of fixative and time of fixation, are critical to guarantee consistent and quality assays, as well as to facilitate interpretation and decrease interobserver variability. Rigorous quality control and centralisation of techniques/interpretation of results are recommended to guarantee consistent assays.

Concordance of clinical and molecular breast cancer subtyping in the context of preoperative chemotherapy response

ER, PR and HER2 status in breast cancer are important markers for the selection of drug therapy. By immunohistochemistry (IHC), three major breast cancer subtypes can be distinguished: Triple negative (TN(IHC)), HER2+(IHC) and Luminal(IHC) (ER+(IHC)/HER2-(IHC)). By using the intrinsic gene set defined by Hu et al. five molecular subtypes (Basal(mRNA), HER2+(mRNA), Luminal A(mRNA), Luminal B(mRNA) and Normal-like(mRNA)) can be defined. We studied the concordance between analogous subtypes and their prediction of response to neoadjuvant chemotherapy. We classified 195 breast tumors by both IHC and mRNA expression analysis of patients who received neoadjuvant treatment at the Netherlands Cancer institute for Stage II-III breast cancer between 2000 and 2007. The pathological complete remission (pCR) rate was used to assess chemotherapy response. The IHC and molecular subtypes showed high concordance with the exception of the HER2+(IHC) group. 60% of the HER2+(IHC) tumors were not classified as HER2+(mRNA). The HER2+(IHC)/Luminal A or B(mRNA) group had a low response rate to a trastuzumab-chemotherapy combination with a pCR rate of 8%, while the HER2+(mRNA) group had a pCR rate of 54%. The Luminal A(mRNA) and Luminal B(mRNA) groups showed similar degrees of response to chemotherapy. Neither the PR status nor the endocrine responsiveness index subdivided the ER+(IHC) tumors accurately into Luminal A(mRNA) and Luminal B(mRNA) groups. Molecular subtyping suggests the existence of a HER2+(IHC)/Luminal(mRNA) group that responds poorly to trastuzumab-based chemotherapy. For Luminal(IHC) and triple negative(IHC) tumors, further subdivision into molecular subgroups does not offer a clear advantage in treatment selection.

Recent trends of HER-2 testing and trastuzumab therapy for breast cancer

Molecular-targeted therapy using trastuzumab, a humanized monoclonal antibody against human epidermal growth factor receptor type-2 (HER-2), is considered to be effective for metastatic as well as primary breast cancer and has already become a worldwide standard therapy for patients with HER-2 protein over-expression and gene amplification. Pretreatment evaluation of HER-2 status is considered to be essential for selection of patients, and according to the generally used algorithm, cases with an immunohistochemistry (IHC) score of 3+ and positivity upon fluorescence in situ hybridization (FISH) are thought to be eligible for trastuzumab therapy. In order to develop an appropriate domestic HER-2 testing system in Japan, the Trastuzumab Pathology Committee was established in 2000 and has been used as a forum for active discussions of policies related to HER-2 testing. After trastuzumab therapy and HER-2 testing had become widely adopted internationally, new guidelines for HER-2 testing were proposed by the ASCO/CAP group in 2007. Since then, these guidelines have gradually become accepted and used in many large-scale clinical studies of HER-2-targeting agents. On the other hand, new ISH methods have been introduced, such as bright-field HER-2 and chromosome 17 centromere double in situ hybridization (BDISH) and dual color-chromogenic in situ hybridization (dc-CISH). These methods make it possible to examine HER-2 gene amplification using only one paraffin section like the dc-FISH method, and to observe grains on the HER-2 gene and centrosome-17 by conventional microscopy. These approaches are considered to be reliable and equally as effective as the dc-FISH method. Accurate evaluation of HER-2 status is thought to be most important for appropriate selection of breast cancer patients who will obtain genuine benefit from trastuzumab treatment. In order to perform effective evaluation of HER-2 status, it is necessary to establish a reliable HER-2 examination system and to maintain its quality at a high level.

Changes in HER2 expression in breast cancer xenografts after therapy can be quantified using PET and (18)F-labeled affibody molecules

In vivo imaging of human epidermal growth factor receptor type 2 (HER2) expression may allow direct assessment of HER2 status in tumor tissue and provide a means to quantify changes in receptor expression after HER2-targeted therapies. This work describes the in vivo characterization of the HER2-specific N-2-(4-(18)F-fluorobenzamido)ethyl]maleimide ((18)F-FBEM)-Z(HER2:342) Affibody molecule and its application to study the effect of 17 (dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG) on HER2 expression by PET.

METHODS

To assess the correlation of signal observed by PET with receptor expression, we administered the tracer to athymic nude mice bearing subcutaneous human breast cancer xenografts with different levels of HER2 expression. To study the downregulation of HER2, we treated the mice with 4 doses (40 mg/kg) of 17-DMAG, an inhibitor of heat-shock protein 90, known to decrease HER2 expression. The animals were scanned before and after treatment. After the last scan, the mice were euthanized and tumors were frozen for receptor analysis.

RESULTS

The tracer was eliminated quickly from the blood and normal tissues, providing high tumor-to-blood and tumor-to-muscle ratios as early as 20 min after injection. The high-contrast images between normal and tumor tissue were recorded for BT474 and MCF7/clone18 tumors. Low but still detectable uptake was observed for MCF7 tumors, and none for MDA-MB-468. The signal correlated with the receptor expression as assessed by immunohistochemistry, Western blot, and enzyme-linked immunosorbent assay. The levels of HER2 expression estimated by post-treatment PET decreased 71% (P < 4 x 10(-6)) and 33% (P < 0.002), respectively, for mice bearing BT474 and MCF7/clone18 tumors. These changes were confirmed by the biodistribution studies, enzyme-linked immunosorbent assay, and Western blot.

CONCLUSION

Our results suggest that the described (18)F-FBEM-Z(HER2:342) Affibody molecule can be used to assess HER2 expression in vivo by PET and monitor possible changes of receptor expression in response to therapeutic interventions.

Disease-free survival according to degree of HER2 amplification for patients treated with adjuvant chemotherapy with or without 1 year of trastuzumab: the HERA Trial

PURPOSE

To determine whether (1) immunohistochemical (IHC) HER2 status (ie, 2+ or 3+), (2) degree of fluorescence in situ hybridization (FISH) amplification according to (2a) HER2/CEP17 ratio or (2b) HER2 gene copy number, or (3) polysomy significantly influenced clinical outcome for patients with human epidermal growth factor receptor 2 (HER2) -positive breast cancer enrolled in the Herceptin Adjuvant trial of trastuzumab versus no trastuzumab administered after completion of chemotherapy.

PATIENTS AND METHODS

IHC and/or FISH analyses were performed locally and required central confirmation as indicating HER2 positivity for trial entry. FISH data from the central HER2 analysis on patients in the 1-year trastuzumab and no trastuzumab arms were assessed in relation to disease-free survival (DFS) after a median 2 years of follow-up.

RESULTS

Central FISH results were available for 2,071 (61%) of the 3,401 patients randomized to the 2 arms. Among patients with FISH-positive disease, (1) the hazard ratios for trastuzumab versus no trastuzumab were 0.56 (95% CI, 0.32 to 0.99) for locally IHC2+ cases (n = 340) and 0.80 (95% CI, 0.40 to 1.61) for centrally IHC2+ cases (n = 299). There was no significant prognostic relationship between (2a) HER2 FISH ratio, (2b) HER2 copy number, or (3) polysomy and DFS in the control arm or predictive relationship defining differential benefit from trastuzumab.

CONCLUSION

There was no evidence for reduced benefit of trastuzumab in HER2 IHC2+FISH+ cases. The degree of HER2 amplification does not influence prognosis or benefit from adjuvant trastuzumab in patients treated with prior adjuvant chemotherapy.

External quality assurance of HER2 FISH and ISH testing: three years of the UK national external quality assurance scheme

The American Society of Clinical Oncology/College of American Pathologists guidelines highlighted the critical importance of quality assurance in diagnostic testing for HER2. Unstained formalin-fixed, paraffin-embedded human breast carcinoma cell line sections were circulated to scheme participants on 9 occasions. "Reference laboratories" reported results for the HER2/chromosome 17 ratio and HER2 copy number for 3 years for each cell line, including 418 sets of results (1,671 results total). The number of participants was 62 laboratories in the final analysis. The mean and SD of results from reference laboratories demonstrated consistency during the 3-year period. The percentage of laboratories achieving "appropriate" results ranged from 45% to 88%, and the percentage achieving "inappropriate" results ranged from 5% to 29%. No consistent effect of the HER2 in situ hybridization testing method was demonstrated. Participation in external quality assurance schemes is a valuable mechanism for demonstrating and acquiring consistency for HER2 testing by in situ hybridization. Poor performance can be corrected via assistance and advice.

Cross-talk between the ErbB/HER family and the type I insulin-like growth factor receptor signaling pathway in breast cancer

Understanding the molecular mechanisms involved in tumorigenesis and their influence on clinical outcome is providing specific molecular markers for targeted therapy. Activation of tyrosine kinase receptors from the human epidermal growth factor receptor family (EGFR, HER2, HER3, HER4) and the insulin-like growth factor receptor I (IGF-IR) plays a key role in the initiation and progression of breast cancer. HER2 overexpression is a validated therapeutic target, as shown by the clinical efficacy of trastuzumab and lapatinib. However, only 25-30% of patients with HER2-overexpressing tumors respond to single-agent trastuzumab or lapatinib, and resistance develops even in responding patients. Therefore, to optimize therapeutic efficacy, it is urgent to elucidate the complex network of signaling pathways that develop in breast cancer cells. Signaling interactions have been reported between ErbB/HER family members and IGF-IR. As increased IGF-IR signaling has been implicated in trastuzumab resistance, agents targeting HER2, and IGF-IR could be potential therapeutic tools in breast cancers that develop resistance to HER2-directed therapy.

Development of automated brightfield double in situ hybridization (BDISH) application for HER2 gene and chromosome 17 centromere (CEN 17) for breast carcinomas and an assay performance comparison to manual dual color HER2 fluorescence in situ hybridization (FISH)

Background

Human epidermal growth factor receptor 2 (HER2) fluorescence in situ hybridization (FISH) is a quantitative assay for selecting breast cancer patients for trastuzumab therapy. However, current HER2 FISH procedures are labor intensive, manual methods that require skilled technologists and specialized fluorescence microscopy. Furthermore, FISH slides cannot be archived for long term storage and review. Our objective was to develop an automated brightfield double in situ hybridization (BDISH) application for HER2 gene and chromosome 17 centromere (CEN 17) and test the assay performance with dual color HER2 FISH evaluated breast carcinomas.

Methods

The BDISH assay was developed with the nick translated dinitrophenyl (DNP)-labeled HER2 DNA probe and DNP-labeled CEN 17 oligoprobe on the Ventana BenchMark^® XT slide processing system. Detection of HER2 and CEN 17 signals was accomplished with the silver acetate, hydroquinone, and H₂O₂ reaction with horseradish peroxidase (HRP) and the fast red and naphthol phosphate reaction with alkaline phosphatise (AP), respectively. The BDISH specificity was optimized with formalin-fixed, paraffin-embedded xenograft tumors, MCF7 (non-amplified HER2 gene) and BT-474 (amplified HER2 gene). Then, the BDISH performance was evaluated with 94 routinely processed breast cancer tissues. Interpretation of HER2 and CEN 17 BDISH slides was conducted by 4 observers using a conventional brightfield microscope without oil immersion objectives.

Results

Sequential hybridization and signal detection for HER2 and CEN 17 ISH demonstrated both DNA targets in the same cells. HER2 signals were visualized as discrete black metallic silver dots while CEN 17 signals were detected as slightly larger red dots. Our study demonstrated a high consensus concordance between HER2 FISH and BDISH results of clinical breast carcinoma cases based on the historical scoring method (98.9%, Simple Kappa = 0.9736, 95% CI = 0.9222 – 1.0000) and the ASCO/CAP scoring method with the FISH equivocal cases (95.7%, Simple Kappa = 0.8993%, 95% CI = 0.8068 – 0.9919) and without the FISH equivocal cases (100%, Simple Kappa = 1.0000%, 95% CI = 1.0000 – 1.0000).

Conclusion

Automated BDISH applications for HER2 and CEN 17 targets were successfully developed and it might be able to replace manual two-color HER2 FISH methods. The application also has the potential to be used for other gene targets. The use of BDISH technology allows the simultaneous analyses of two DNA targets within the context of tissue morphological observation.

Delineation of HER2 gene status in breast carcinoma by silver in situ hybridization is reproducible among laboratories and pathologists

An automated enzyme metallographic silver in situ hybridization method (SISH) has been reported to successfully determine human epidermal growth factor receptor 2 (HER2) gene amplification. We evaluated the staining and interpretative reproducibility of the HER2 SISH assay at five laboratories and compared SISH results with other in situ hybridization (ISH) methods. The HER2 gene status of 89 breast carcinomas was analyzed in parallel using manual dual-color fluorescence ISH, manual chromogenic ISH, and bright-field automated SISH. A total of 1098 SISH-stained slides were evaluated. For comparison, all specimens were stained by 4B5 immunohistochemistry for HER2 protein expression. Interpretation was performed by pathologists at five different laboratories using the algorithms provided by the manufacturers and the guidelines of American Society of Clinical Oncology/College of American Pathologists. Staining and interpretative reproducibility were measured through the computation of weighted kappa statistics. Following the optimization of SISH staining, 1077/1098 (98%) of slides were evaluable. Excellent reproducibility and efficacy of HER2 SISH staining, and interobserver interpretation (Kw = 0.91), were observed among five sites. For the 89 invasive breast cancer cases, the overall rate of concordance between consensus 4B5 and consensus SISH, fluorescence ISH, and chromogenic ISH was 96.6% (86/89), 97.8% (87/89), and 96.6% (86/89), respectively. Overall concordance between positive and negative SISH and fluorescence ISH results, as well as between individual and consensus positive and negative SISH results, was excellent (P < 0.001).

KRAS mutation testing for predicting response to anti-EGFR therapy for colorectal carcinoma: proposal for an European quality assurance program

Novel therapeutic agents targeting the epidermal growth factor receptor (EGFR) have improved outcomes for patients with colorectal carcinoma. However, these therapies are effective only in a subset of patients. Activating mutations in the KRAS gene are found in 30-40% of colorectal tumors and are associated with poor response to anti-EGFR therapies. Thus, KRAS mutation status can predict which patient may or may not benefit from anti-EGFR therapy. Although many diagnostic tools have been developed for KRAS mutation analysis, validated methods and standardized testing procedures are lacking. This poses a challenge for the optimal use of anti-EGFR therapies in the management of colorectal carcinoma. Here we review the molecular basis of EGFR-targeted therapies and the resistance to treatment conferred by KRAS mutations. We also present guideline recommendations and a proposal for a European quality assurance program to help ensure accuracy and proficiency in KRAS mutation testing across the European Union.

EGFR/HER2 in breast cancer: a biological approach for molecular diagnosis and therapy

Novel cancer therapies have focused on specific molecular markers present in malignant tumors. The rationale of targeted therapy relies on the knowledge of molecular mechanisms involved in carcinogenesis and their influence in clinical outcome allied to a more specific and less toxic treatment. Activation of EGF receptor and HER2 is an important factor for initiation and progression of malignancies, including breast cancer where the status of HER2 is an essential step in the diagnostic workup; EGFR overexpression has been associated to the so-called basal-like breast carcinomas, which opens a new avenue for diagnosis and therapeutic approach in these tumors. This review will focus on mechanisms of HER2 and EGF receptor upregulation, the targeted therapies that are currently in use for these receptors, possible combined therapies, as well as the approach for molecular diagnosis from the pathologist's point of view.

Chromogenic in situ hybridisation for the assessment of HER2 status in breast cancer: an international validation ring study

Introduction

Before any new methodology can be introduced into the routine diagnostic setting it must be technically validated against the established standards. To this end, a ring study involving five international pathology laboratories was initiated to validate chromogenic in situ hybridisation (CISH) against fluorescence in situ hybridisation (FISH) and immunohistochemistry (IHC) as a test for assessing human epidermal growth factor receptor 2 (HER2) status in breast cancer.

Methods

Each laboratory performed CISH, FISH and IHC on its own samples. Unstained sections from each case were also sent to another participating laboratory for blinded retesting by CISH ('outside CISH').

Results

A total of 211 invasive breast carcinoma cases were tested. In 76 cases with high amplification (HER2/CEP17 ratio >4.0) by FISH, 73 cases (96%) scored positive (scores ≥ 6) by 'outside CISH'. For FISH-negative cases (HER2/CEP17 ratio <2.0), 94 of 100 cases (94%) had CISH scores indicating no amplification (score ≤ 5), and only three cases were positive by CISH; in the three remaining cases, no CISH result could be obtained. For cases with low-level amplification using FISH (HER2/CEP17 ratio 2.0–4.0), 20 of 35 had CISH scores indicating gene amplification. Inter-laboratory concordance was also very high: 95% for normal HER2 copy number (1–5 copies); and 92% for cases with HER2 copy numbers ≥ 6. CISH intra-laboratory concordance with IHC was 92% for IHC-negative cases (IHC 0/1+) and 91% for IHC 3+ cases. Among IHC 2+ cases, CISH was 100% concordant with samples showing high amplification by FISH, and 94% concordant with FISH-negative samples.

Conclusion

These results show that CISH inter- and intra-laboratory concordance to FISH and IHC is very high, even in equivocal IHC 2+ cases. Therefore, we conclude that CISH is a methodology that is a viable alternative to FISH in the HER2 testing algorithm.