Assessment and prognostic impact of a new classification using HER2 and HER3 status in resected gastric cancer in a european cohort.

65Background: HER2 status is a predictive biomarker to response to trastuzumab in metastatic gastric adenocarcinomas. However, relatively little is known about the role of HER2 and HER3 in the non-metastatic disease in European population. Methods: Immunohistochemical expression of HER2 was analyzed using DAKO-HercepTest™ and gene amplification using DAKO-DuoCISH kit; both was scored according to published reports. HER3 expression was analyzed using HER3 clon DAK-H3-ICHER3 and scored as follows: 0 = no staining, 1+ = light staining, 2+ = moderate staining, and 3+ = strong staining. Slides with score 0 or 1+ were classified as low expression or negative and slides with score 2-3+, as high expression or positive. According HER2 and HER3 status patients were classified into six subtypes: HER2-HER3 negative, HER2 equivocal expression HER3 negative, HER2 positive – HER3 negative, HER2 negative – HER3 positive, HER2 equivocal expression – HER3 positive and HER2-HER3 positive. The relationship between this class...