HER2 Status in Oesophagogastric Junction and Gastric Cancer - the Irish Landscape

ABSTRACT HER2 is overexpressed in ∼ 7-34% of gastroesophageal (GE) adenocarcinomas. The ToGA study, established the benefit of trastuzumab in combination with chemotherapy in HER2(+) metastatic GE tumours. In this study, 22% of patients were HER2(+) {immunohistochemistry (IHC)3+ or fluorescence insitu hybridization (FISH)(+)}. We report a multi-center Irish experience by examining HER2 status by IHC and FISH in GE tumours. Methods Database from three regional cancer centres were examined to identify pts with junctional or gastric adenocarcinoma. HER2 testing was performed on biopsy or resection specimens of patients with early stage and metastatic GE tumors between 2008–2011. We defined HER2 positive as IHC3+ or FISH(+) {HER2:17ch ≥ 2}. In addition, age, gender, histology, stage of disease, were recorded. Clinicopathologic characteristics were extracted and compared with t-test or Fisheru0027s exact as appropriate. Results Between 2008 and 2011, 177 pts were identified. Median age was 68 years (range: 25 – 96), 36% were male. Gastric tumours were identified in 51%, while 53% were metastatic at diagnosis. Median number of metastatic sites was 1 (0 – 4). IHC and FISH were performed on 170 pts (96%) and 131 (74%) of patients. Distribution of IHC score of 0, 1, 2 and 3 were 38%, 32%, 19% and 11%, respectively. With respect to tumour heterogeneity of HER2 amplification, in IHC3 + , 50% were FISH(+), IHC2 + , 21.1% were FISH(+) and IHC1 + , 3.7% were FISH(+). Overall HER2(+) rate for the cohort was 16.4% (n = 29). Comparing patients with HER2(+) and HER2(-)disease, gender (males, 38 vs 38%, p = .84), age(69 vs 68, p = .79) and site distribution gastric, (45 vs 52%, p = .54) were identical .The rate of metastasis at diagnosis were similar, at 54 vs 53%. Presence of metastases in the liver (69 vs 48%, p = .22), peritoneum (38 vs 49%, p = .55), brain (8 vs 3%, p = .44) were comparable in both patient cohorts. Conclusions HER2(+) GE adenocarcinomas in the analyzed cohort displays similar pattern of heterogeneity in IHC staining and FISH positivity but with lower incidence (16.4%) of HER2 amplification than was reported in the ToGA study. Further analysis did not identify differences in clincopathologic characteristics in HER2 + ve patients. Disclosure All authors have declared no conflicts of interest.