Assessment of HER2 status from an epidemiology study in tumor tissue samples of gastric and gastro-esophageal junction cancer: Spanish results of the HER-EAGLE study.

4089 Background: Overexpression of HER2 is an important biomarker in gastroesophageal junction (GEJ) and gastric cancer (GC) and a predictive factor for trastuzumab (T, Herceptin). The ToGA phase III trial showed the benefit in overall survival of adding trastuzumab to chemotherapy inHER2-positive advanced GEJ/GC patients, following validated scoring criteria by a central laboratory. This study examines the incidence of HER2 positivity (local laboratories) in GEJ/GC according to EMA Herceptin label. Methods: HER-EAGLE was an epidemiological, non–interventional, international study assessing HER2 status by IHC/ISH in tumor samples from any stage GEJ/GC patients. Neutral buffered 10% formalin embedded tissues (surgical excision specimens or minimum 6-8 biopsies) analyzed via validated Ventana and Dako methods and scoring criteria used in ToGA: HER2-positive if IHC 3+ or IHC 2+ (FISH/SISH confirmed; HER2/CEP17 ratio ≥ 2.0); HER2-negative if IHC 0 or IHC 1+. Overall and subgroup estimates calculated with 95%CI. Data from the Spanish cohort are presented. Results: The Spanish cohort of HER-EAGLE included 1,954 participants (63.7% males) from 33 hospitals (Dec2010 to Aug2011), with 469 biopsies (24.0%) and 1,479 excisions (75.7%). Samples were 13.7% GEJ and 86.3% GC, and the adenocarcinomas were 1,137 intestinal (58.2%), 510 diffused (26.1%), 163 mixed (8.3%; Laureen classification), and 144 not available (7.3%). Median time from sampling to HER2 analysis of 5.1 years (range from days to 12 years). Total of 210 cases tested IHC 3+ (10.7%), 215 IHC 2+ (11.0%), 308 IHC 1+ (15.8%), and 1,221 IHC 0 (62.5%). Overall, HER2 positivity (IHC 3+ or IHC2+/ISH+) was 14.1% (95%CI 12.61 – 15.75). HER2 positivity by histological type was higher in intestinal adenocarcinomas (19.5%) compared to diffused (4.5%) or in mixed (9.2%). Conclusions: HER-EAGLE confirmed the feasibility of community based HER2 testing in GC as the first study with a high number of samples analyzed by local laboratories. The incidence of HER2-positivity (EMA label definition) was similar to the ToGA screening population, and it was again higher in adenocarcinomas of intestinal type (19.5%).