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Abstract 3423:HER2amplification and microsatellite status distribution in Chinese gastric cancer patients

Background:Amplification and/or overexpression of human epidermal growth factor receptor-2 (HER2, also known as ERBB2) were present in 6.1-23.0% of gastric cancer. In breast cancer, amplification and overexpression of the HER2 are associated with poor prognosis. Meanwhile, MSI-H patients have an improved prognosis in gastric cancer. However, little is known about the association of these two indicators in gastric cancer. Method:260 tumor tissues and matched normal from gastric cancer patients were included in this study to reveal HER2 amplification and microsatellite status distribution of Chinese patients with gastric cancer using deep next generation sequencing (NGS) targeting 450 cancer genes. Microsatellite status (MSS or MSI-H) were evaluated according to NGS algorithms. Result:Male to female ratio was about 2:1 with a mean age of 60 years old. 241 tumors were primary tumors and 19 were metastases. MSI-H was detected in 16 samples (6.2%) and HER2 amplification was detected in 18 samples (6.9%), which were consistent with the previously reported incidences. The proportion of MSI-H in metastatic lesions was higher than that in primary lesions, but the difference was not statistically significant (10.5% vs. 5.8%, P=0.33). The detection of HER2 amplification in metastatic foci and primary tumors had a similar trend as that in MSI-H (15.8% for metastatic foci vs. 6.2% for primary tumors, P=0.13). Interestingly, our study revealed that HER2 amplification was mutually exclusive with MSI-H in both primary and metastatic lesions. MSI-H/HER2amp-, MSS/HER2amp+, and MSS/HER2amp- subgroups accounted for 5.8%, 6.2%, and 88% in primary cancers, while MSI-H/HER2amp-, MSS/HER2amp+ and MSS/HER2amp- subgroups accounted for 10.5%, 15.8% and 73.7% in metastasis, respectively. Conclusion:We analyzed the distribution of HER2 amplifications and microsatellite status in Chinese patients with gastric cancer. The detection rate of HER2 amplifications and MSI-H was consistent with previous reports. Interestingly, our data showed that both HER2 amplifications and MSI-H have higher detection rate in metastases than that in primary lesions, and the two biomarkers were mutual exclusive in our cohort. Citation Format: Jun Guo, Da Jiang, Wei Zhang, Ting Deng, Zhaojian Niu, Wenting Chen, Junping Shi, Shuirong Zhang, Lin Zhang. HER2 amplification and microsatellite status distribution in Chinese gastric cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3423.