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Background: Trastuzumab plus chemotherapy is the treatment of choice for locally advanced or metastatic gastric cancer patients. Pathological assessment of gastric cancer specimens hoever still remains difficult albeit it is a crucial prerequisite for optimal treatment. Methods: This registry as designed as a prospective, observational, multi-center research initiative comparing HER2 test results obtained from the local pathology department and to reevaluate HER2 testing in a central pathology laboratory. HER2 testing as performed by means of immunohistochemistry IHC and in equivocal cases Score 2+ in addition by in-situ hybridization ISH .In the central laboratory HER2 IHC as carried out using the HER-2neu 4B5 Rabbit Monoclonal Primary Antibody. In the local pathologies up to four different kits ere used.The rate of HER2 positive locally advanced or metastatic gastric or GEJ cancer is the primary study objective. Comparison of HER2 results from local and central labs, safety, PFS, OS and type of chemoimmunotherapy in HER2 positive patients are additional objectives. Results: Up to no samples of 127 patients have been tested in local and central pathology respectively. Median age as 68 years, median eight 68 kg. 59 patients already had at least one prior treatment for metastatic disease. 20 out of 127 tested samples 15.7 percent shoed discordance beteen central and local testing ith 6127 4.7 percent false negative results and 14127 11.0 percent false positive results. 37 patients 29.0 percent tested HER2 positive in local pathology. 30 of hich ere treated ith trastuzumab in combination ith different chemotherapy backbones 53.3 percent first line . Median PFS as 6.5 months, overall survival as 12.0 months. PFS and OS ere shorter in patients ith false positive results 5.7 and 7.6 months, respectively . Conclusions: This ongoing registry points to the fact that HER2 testing in gastric cancer is difficult, and highlights the necessity for quality insurance to optimize individual treatment options. Although different chemotherapy backbones are used PFS is similar to published data.,J Clin Oncol 34, 2016 suppl; abstr e15501 ,Publication Only Gastrointestinal Noncolorectal Cancer