Update on HER2 Testing for Breast and Upper Gastrointestinal Tract Cancers

Abstract

With the regulatory approvals in Europe and the USA of trastuzumab-based anti-HER2 targeted therapy for upper gastrointestinal cancers in 2010, HER2 testing has now become universal for newly diagnosed cases of both breast cancer and adenocarcinomas of esophagus, stomach and gastroesophageal origin. In the 12 years or more since the approval of trastuzumab for breast cancer, general refinements in approaches to HER2 testing, including a greater understanding of the implications of preanalytic factors impacting the test results and the application of standardization of reporting of HER2 test results, have taken place. There has also been continuing development in breast cancer with the introduction of new HER2 tests, including non-FISH tests, dimerization assays, phosphorylated HER2 receptor tests, mRNA-based tests, HER2 gene sequencing tests and the application of HER2 testing to circulating tumor cells. Most recently, the introduction of HER2 testing for upper gastrointentinal malignancies has emphasized the need for performing and interpreting slide-based assays in a manner unique to these specimens and not to apply the breast cancer testing protocols to esophageal and gastric adenocarcinomas.

KEYWORDS::

• breast cancer
• chromogenic in situ hybridization
• concordance
• esophageal cancer
• FISH
• HER2
• immunohistochemistry
• stomach cancer
• testing

Financial & competing interests disclosure

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.