Trastuzumab plus chemotherapy based on the accurate HER2-positivity testing for patients with advanced gastric cancer.

e15075 Background: Accurate HER2 testing in patients with gastric cancer is difficult due to HER2 heterogeneity and incomplete membrane staining in gastric cancer. Our previous study showed that the frequency of the HER2-positivity for 198 gastric cancer samples was identified in 5.1-6.1% (10-12/198) under several IHC conditions, less than the 28.1% observed in the Japanese subgroup analyses of the ToGA study. The aim of the present study was to investigate therapeutic responses based on the results from the HER2-positivity testing in patients with advanced gastric cancer (AGC). Methods: From September 2011 to September 2013, HER2-positivity was evaluated for 32 patients with nonresectable AGC. Objective responses and survival data were evaluated in these patients with AGC who were treated with chemotherapy plus trastuzumab or chemotherapy alone based on the HER2-positivity testing. Results: Of all patients with AGC, eleven patients with HER2-positive tumors were treated with capecitabine or S-1 / cisplat...