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Clinicopathological Factors in Relation to HER2 Status in Metastatic Gastric Cancer: A Retrospective Observational Study

ABS TRACT Objective: Data available on the rate of human epidermal growth factor receptor 2 (HER2) positivity and clinicopathological parameters related to it are heterogeneous. Hence, it is pertinent to investigate these parameters in different populations. This study aims to determine the frequency of HER2 positivity and clinicopathological factors associated with it in metastatic gastric cancer patients in a Turk- ish population. Material and Methods: This study included 552 patients with metastatic gastric cancer from 5 oncology centers. HER2 status, age, gender, smoking and alcohol history, body mass index, basal carcino embryonic antigen (CEA) level, basal cancer antigen 19-9 (CA 19-9) level, tumor localization, de-novo metastatic cancer, Lauren classification, signet-ring cell component, venous and neural invasion, and histological grade data were collected retrospectively. HER2 positivity was defined as an immunohistochemistry (IHC) score of 3+ or an IHC score of 2+ and in situ hybridization positive. Univariable and multivariable logistic regression analyses were used to detect clinicopathological factors associated with HER2 status. Results: A total of 100 patients (18.1%) were HER2-positive. Alcohol consumption, basal CEA level, basal CA 19-9 level, and signet-ring cell component were found to be statistically significant in univariable analysis. Alcohol use, basal CEA level, and having signet-ring cell component were statistically significant in the multivariable analysis. Odds ratios of alcohol use, high basal CEA and having signet-ring component were 2.35 (95% confidence interval (CI): 1.27-4.36, p=0.006), 1.99 (95% CI: 1.19-3.36, p=0.009), and 0.39 (95% CI: 0.22-0.71, p=0.002) respectively. Conclusion: HER2 positivity was detected in 18.1% of metastatic gastric cancer patients in the Turkish population. Alcohol use and basal CEA level were positively, and the signet-ring cell component was negatively correlated with HER2 positivity.