HER2 testing in gastric and gastroesophageal junction adenocarcinomas

Abstract HER2 evaluation has become standard practice in metastatic gastric and gastroesophageal junction (GEJ) adenocarcinomas. In 2010, the international ToGA (Trastuzumab for Gastric Cancer) trial demonstrated improved survival in patients with HER2 overexpressing gastric and GEJ adenocarcinomas who were treated with trastuzumab (Herceptin ® ) in combination with standard chemotherapy. The evaluation of HER2 in gastric and GEJ adenocarcinomas has several key differences compared to the HER2 evaluation that has been traditionally performed for breast carcinomas. In addition to differences in immunohistochemistry scoring, there are also differences in judging adequacy of biopsy specimens. Furthermore, the routine evaluation of HER2 expression in gastric and GEJ adenocarcinomas is still relatively new and widespread programs for quality assessment have not been well established. This review examines the critical issues to consider in the implementation of HER2 evaluation for gastric and GEJ adenocarcinomas.