HER2 status in gastric/gastro-oesophageal junctional cancers: should determination of gene amplification by SISH use HER2 copy number or HER2:CEP17 ratio?

doi:10.1097/PAT.0000000000000075

Pathology

Volume 46, Issue 3, April 2014, Pages 184-187

https://doi.org/10.1097/PAT.0000000000000075 Get rights and content

Summary

The aim of this study was to compare HER2 amplification, as determined by the HER2 copy number (CN) and the HER2/ CEP17 ratio, with protein expression in gastric and gastro-oesophageal junction (G/GOJ) adenocarcinoma. HER2 immunohistochemistry (IHC) and silver in situ hybridisation (SISH) were performed in 185 cases. Modified gastric criteria were used for IHC scoring. HER2 and CEP17 CNs were counted in at least 20 cancer cells and the ratio calculated as per previously defined protocols. These two SISH methods were statistically compared against the different IHC scores. Thirty-four cases showed amplification, by both methods in 29, and either method in five. IHC score was 3+ in 29 cases; 26 showed amplification by both methods, one by ratio only and two were not amplified. IHC score was 2+ in 24 cases; three showed amplification by both methods and two by either. One each of IHC 1+ and 0 showed an increased ratio but not CN. The HER2 CN and ratio for IHC score 3+ compared to scores 2+, 1+ and 0 were significantly different (all p<0.01). The CN for IHC 2+ vs IHC 1+ and IHC 0 was significantly different (both p<0.01) but the ratio was not (p=0.5711 and p=0.2857, respectively). The CN and the ratio for scores 1+ and 0 were not significantly different (p=0.9823 and p=0.9910, respectively). The HER2 CN differentiates between the different IHC scores better than the HER2:CEP17 ratio. Cases that show IHC3+ and high CN may not require calculation of the ratio. Furthermore, consideration should be given to the CN when IHC negative cases appear amplified by the ratio only.

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Citation Excerpt :
True polysomy is believed to be rare in GAC.45 The importance of considering the absolute HER2 gene copy number in the final consideration of HER2 status was emphasized in Australian studies.13,15,46 Consideration should be given to the copy number when IHC-negative or equivocal cases appear amplified by the ratio only.
Human epidermal growth factor receptor 2 (HER2) status determines gastric/gastroesophageal junction (GEJ) adenocarcinomas that benefit from targeted therapy; hence, HER2 testing has become a routine practice. Accurate HER2 testing is fundamental to select eligible patients who will benefit from HER2-targeted treatment. The reported HER2-positive rate in gastric/GEJ cancers ranges from 4.4% to 53.4%, and HER2-positive tumors are considered to have more-aggressive biologic behavior and tumor recurrence. Main modalities of HER2 testing in clinical practice include immunohistochemistry (IHC) for protein expression and in situ hybridization (ISH) for gene amplification. Many technical pitfalls affect the accuracy of HER2 result. Additionally, several issues in HER2 testing are related to the tumor biology, sample selection, interpretation of IHC and ISH results, and confirming HER2 status. Therefore, gastric/GEJ adenocarcinoma-specific HER2 testing protocols have been developed and standardized to minimize the impact of these preanalytical and analytical factors and to enhance reproducibility of HER2 testing results. This review provides up-to-date practical guidance to clinicians on accurate HER2 testing and interpretation of results in gastric/GEJ adenocarcinoma.
HER2 testing in advanced gastric and gastro-oesophageal cancer: analysis of an Australia-wide testing program
2017, Pathology
Citation Excerpt :
There has been no universally accepted definition of HER2 positive status: it has been defined by protein expression with an IHC 3+ result or a HER2:chromosome enumeration probe 17 (CEP17) ratio by ISH of ≥2 alone, or a combination of IHC, HER2:CEP17 ratio and HER2 copy number (CN).6–10 In addition to issues with cut-off, there are limited evidence-based scientific data on practical issues in testing, such as tissue fixation, selection of sample type (endoscopic biopsies, resections, metastatic sites including cytology samples), quantity and quality of tumour tissue samples and impact of heterogeneity on results.9,11–16 Implementation of biomarker protocols including HER2 testing in GOJ cancers is lagging, even in specialist centres.17
This Australian human epidermal growth factor receptor 2 (HER2) testing program aimed to analyse >800 cases tested in a coordinated setting to further evaluate the criteria to establish HER2 status in advanced gastric and gastro-oesophageal junction (GOJ) cancer. Heterogeneity, and minimum number of biopsy fragments for reliable HER2 assessment were also examined in a subset of samples.
Five laboratories tested 891 samples referred to determine HER2 status for potential anti-HER2 treatment. Cancer site, specimen type (endoscopic biopsy/resection/metastases), immunohistochemistry (IHC) score, HER2 gene and CEP17 copy number (CN) and HER2:CEP17 ratios were recorded. Samples were derived from stomach (53.1%), GOJ (28.2%) or metastases (18.5%). IHC for HER2 and dual probe HER2:CEP17 in situ hybridisation (ISH) were performed in parallel. A stringent definition (SD) of HER2 positivity was used (IHC2+/3+ plus CN>6 and ratio>2) and compared with other published criteria.
HER2 positive rate was 13.9% (114/820) by SD, and 12.9–16.0% using other definitions. There was higher concordance between IHC and HER2 CN by ISH than with ratio. The HER2 positive rate was significantly higher in GOJ samples than others (p = 0.03) and in endoscopic biopsies than resections (p = 0.047). In a subset of 98 positive cases, 39 (39.8%) showed heterogeneity, and in 282 endoscopic biopsies positivity rate plateaued at five tumour fragments, suggesting this is the minimum number of biopsies that should be examined.
Concordance of HER2 expression in paired primary and metastatic sites of gastric and gastro-oesophageal junction cancers
2015, Pathology
HER2 is amplified/overexpressed in a subset of gastric and gastro-oesophageal junction cancers. Addition of anti-HER2 therapy has been shown to provide survival benefit in this setting. However, there are limited data assessing the concordance of HER2 status between primary and metastatic sites. A total of 113 samples from 43 paired primary and metastatic tumours were tested for HER2 status, by immunohistochemistry (IHC) for protein expression and silver in situ hybridisation (SISH) for gene amplification. Primary sites tested included endoscopic biopsies (n = 30) and resections (n = 24). Metastatic samples included lymph nodes (n = 29), peritoneal effusions (n = 21) and miscellaneous sites (n = 9). The overall HER2+ rate was 11%. Of 41 (95%; 95% CI 88.5–100%) concordant cases, 38 were HER2– and three were HER2+. There were two (5%) discordant cases, one of which showed heterogeneity of HER2 expression. This series confirms a high concordance rate of 95%, supporting that testing of primary tumours and metastases is equally valid and providing clinical rationale for the addition of anti-HER2 therapy in HER2+ disseminated disease.
Predictive marker: HER2 in esophageal adenocarcinoma
2018, Methods in Molecular Biology
Somatic DNA copy-number alterations detection for esophageal adenocarcinoma using digital polymerase chain reaction
2018, Methods in Molecular Biology

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HER2 status in gastric/gastro-oesophageal junctional cancers: should determination of gene amplification by SISH use HER2 copy number or HER2:CEP17 ratio?

Summary

Mod Pathol

Lancet

Hum Pathol

Ann Oncol

Hum Pathol

Gastric HER2 Testing Study (GaTHER): an evaluation of gastric/gastroesophageal junction cancer testing accuracy in Australia

Am J Surg Pathol