Iier2 Status In Gastroesophageal Cancer: An Irish Multicenter Experience

28 Background: Gastroesophageal cancer is a major cause of cancer-related mortality. The ToGA study, established the benefit of trastuzumab in combination with chemotherapy in HER2 positive metastatic gastroesophageal tumors. We report a multi-centre Irish experience of examining HER2 status by IHC and FISH amongst gastroesophageal adenocarcinomas. Methods: HER2 testing was performed on biopsy or resection specimens of patients with early stage and metastatic gastroesophageal tumors between 2010 and 2012. We defined HER2 positive(+) as IHC3+ or FISH(+) {HER2:17ch ≥2}. All specimens which were IHC2+ or IHC3+, where treatment with trastuzumab was under consideration, went on to have FISH testing. Results: Between 2010 and 2012 HER2 status was established in all patients presenting with biopsy proven gastroesophageal cancers, this amounted to 88 patients (53 gastric, 35 esophageal). Within the population examined 64% of patients had metastatic disease. The majority (51%) had intestinal type adenocarcinomas, the remainder having diffuse type (16%), mixed type (3%) or undetermined (18%). Nineteen patients (21%) were defined as being HER2+ (14 male, 5 female). Four were FISH (+) IHC3+, five were FISH (+) IHC2+ and in ten patients HER2 status was defined by IHC3+ alone as FISH testing was indeterminate (1 patient) or not tested (9 patients). In the subset of HER2+ patients (19 patients), the majority had gastric cancer (63%). Intestinal type adenocarcinoma occurred in 12 patients (63%), the remainder being diffuse type (2 patients), mixed (1 patient) or undetermined (4 patients). Seven patients (36%) had localized disease. In the metastatic cases the distribution of metastases was as follows: 9(47%) liver, 3(15%) lung, 3(15%) peritoneal, 1(5%) adrenal, 1(5%) brain and 1(5%) ovarian. Five patients are receiving trastuzumab for HER2+ disease in combination with cisplatin and fluorouracil based chemotherapy. Conclusions: In a cohort of Irish patients we found similar levels of HER2+ gastroesophageal cancers (21%) as that demonstrated in the ToGA trial (22%). Clinicopathologic characteristics were broadly similar also. Outcome of our experience with HER2 directed therapy will be reported.