Comparison of HER-2 expression in diagnostic biopsies and surgical specimens of gastric and esophageal adenocarcinoma: Influence of neoadjuvant chemotherapy

18 Background: HER-2 is overexpressed in 15 to 20% of gastric and esophageal adenocarcinoma (ADK), and is a target for trastuzumab in metastatic patients (Bang YJ et al, Lancet 2010). The main objective of this study was to compare HER-2 expression between diagnostic biopsies and surgical specimens of gastric ADK, and to determine the influence of non-trastuzumab containing neoadjuvant chemotherapy (NAC) on this expression. Methods: Pathological specimens and biopsies of patients operated on with a curative aim in two French hospitals (Institut Mutualiste Montsouris and Saint-Antoine hospital) between 2004 and 2011 were collected; two cohorts treated or not with a NAC were constituted. Blind HER-2 analyses on biopsies and on surgical specimens were performed using IHC and ISH methods, with two independent pathological readings. HER-2 overexpression was defined by a score 3+ in IHC, or by a score 2+ in IHC with a positive ISH test. Results: Paired samples of 201 patients wereanalyzed. HER-2 overexpression rates were 16.4% on biopsies and 19.4% on surgical specimens. HER-2 positive tumors were mainly cardial or esophageal tumors, with a well-differentiated, intestinal histological type. Surgical specimens seemed to allow better identification of HER-2 positive tumors than diagnostic biopsies for patients that had not received NAC (13.5% of HER-2 positivity on biopsies versus 24.3% on surgical specimens), whereas this trend was reversed for patients with NAC (18.1% of HER-2 positivity on biopsies versus 16.5% on surgical specimens). HER-2 status differed between biopsies and surgical specimens in 10% of patients. Conclusions: The determination of HER-2 status on biopsies provides results that completed those obtained with the analysis of surgical specimens. Analyzed only on surgical specimens, HER-2 status is underestimated in particular after NAC. This study suggests the interest of repeating HER-2 evaluations to optimize the identification of patients that can benefit from trastuzumab treatment.