HER2 Expression in Gastric Adenocarcinoma-a Study in a Tertiary Care Centre in South India

According to the literature available, HER2(human epidermal growth factor 2)status in gastric carcinoma has been studied worldwide, however there is a paucity of published data from India. Hence, this study was taken up to evaluate HER2 overexpression in gastric adenocarcinoma patients and to assess the relationship between its expression and clinicopathological tumor parameters. Prospective study was conducted in a teaching hospital over a period of 27 months. Total or subtotal gastrectomy resection specimens and small biopsies were included in the study. Immunohistochemistry (IHC) was carried out on all the cases to evaluate the expression of HER2 in formalin-fixed paraffin-embedded tissue samples. Fluorescence Insitu Hybridization (FISH) was done for equivocal cases on IHC. The data was analyzed using Chi square test / Fisher's Exact Test. Odds ratio was computed between HER2 and other pathologic variables. HER2 overexpression was confirmed in 16 (27.6 %) cases of which 15 (93.8 %) cases were of intestinal type whereas only 1 (6.2 %) case of diffuse type adenocarcinoma. Hence, HER2 positivity was significantly more common in the intestinal type of gastric cancer compared to the diffuse type (p = 0.045). Positivity of HER2 was more in small biopsies as compared to the resection specimens in this study but the p value was not significant. There was no difference in HER2 overexpression in relation to the age, gender, tumor site, tumor differentiation and stage. HER2 overexpression is more prevalent in the intestinal subtype. The relatively high percentage of HER2 positive tumors may provide a useful target for immunotherapy of these cancers.