Prevalence of HER2/neu overexpression/amplification in a Hispanic population with gastric adenocarcinoma.

Abstract

25 Background: In Europe, Asia, and North America, studies have identified that approximately 20% of patients with gastric adenocarcinoma exhibit overexpression of HER2/neu. This group of patients has been shown to benefit from combination therapy with the anti-HER2/neu monoclonal antibody trastuzumab. These findings have not been studied in Hispanics who may possess a distinct gastric cancer genotype. The aim of this study is to determine the rate of HER2/neu positivity in a completely Hispanic population with gastric adenocarcinoma and to analyze the clinical factors associated with HER2/neu. Methods: We conducted a retrospective study in three different hospitals in Monterrey, Mexico. The study population consisted of Hispanic patients with gastric adenocarcinoma who have had a gastric resection and for whom there were adequate amounts of tissue available in paraffin blocks. Tissue was tested for HER2/neu using both Immunohistochemistry (IHC) and the fluorescent in situ hybridization (FISH) techniques. Results: From 2000 to 2010, we initially evaluated 27 gastric cancer tumor samples. Sex distribution was 15 males and 12 females with a mean age of 57±15 (SD) years. Anatomic distribution of tumor was 4% in the cardias, 40% in the body and 56% in the antrum. Lauren's histological type distribution was 52% diffuse and 48% intestinal. Fifty-three percent of the tumors were high grade and nodal positivity was present in 69%. Overexpression of Her-2/neu (IHC ++ and +++) was found in five (17.4%) of the samples, being moderate (++) in two (7.4%) and strong (+++) in three (11%) tumor samples. FISH amplification for the HER2/neu gene was found in two (7.4%) tumors and was only seen in samples with a strong (+++) IHC result. There was no association identified between HER2/neu status with age, gender, degree of differentiation, T stage, or nodal status. Conclusions: In a homogeneous Hispanic population, 17.4% of gastric cancer patients were found to overexpress HER2/neu by IHC. FISH did not identify any additional HER2/neu positive tumors. It is important to consider IHC testing for HER2/neu in Hispanic gastric cancer patients as they could benefit from a chemotherapy regimen containing trastuzumab. No significant financial relationships to disclose.