P-0065 Determination of the HER2 Expression in Chilean Patients with Gastric Cancer

Abstract

IntroductionGastric Cancer is a common disease in Chile, with one of the highest mortality rates related to this diagnosis in the world, 20 per 100,000 people). Some years ago groups studied the expression of HER2, for prognostic and therapeutic implications. A recently published ToGa study demonstrated the benefits in the overall survival in patients with overexpression of the mentioned receptor treated with trastuzumab combined and chemotherapy, overexpression presented in 20% of the studied population. In Chile, the frequency of this expression is unknown. The objective of this study is determine the frequency of the HER2 overexpression in gastric cancer patients diagnosed at the Hospital of the University of Chile in the different stages of diagnosis. MethodsDescriptive, retrospective study, in which the clinical history and tumor samples from patients with gastric cancer diagnosed between 2008 and 2010 was collected prior informed consent. There were 73 samples analyzed, obtained from tissue blocks in paraffin. Cuts of 4 microns thick were performed and placed on slides impregnated in xylene. For the immunohistochemical study it was used the commercial kit HercepTest® (DAKO). ResultsWe studied 73 patients studied, 50 men (68%) and 23 women (32%). They corresponded to stage I 8,2%, stage II 12,3%, stage III 34,2% and stage IV 45,8% (AJCC Cancer Staging Manual, 6° edition 2002). All of them were adenocarcinoma. Regarding the HER2 status, six cases (8%) had full staining of the high intensity membrane (score 3+), 3 cases had full staining but with low to moderate intensity (score 2+) and 2 cases presented a focal and incomplete pattern of the membrane (score 1+). Among the cases with scores 3+, 2 had an homogeneous staining pattern in the sample, while the rest was with an heterogeneous pattern. From the 6 positive cases, two were mildly differentiated and the rest poorly differentiated. Three of the six samples corresponded to the intestinal type, whereas was diffuse. Likewise, among the positive cases, 4 were stage IV, one in stage III and one in stage II. The 3 cases with HercepTest 2+ were studied with FISH, one resulted positive and the other two samples were unsatisfactory. Finally, the positivity for HER 2 in this study was of 7 cases (6 IHQ 3+ and one case 2+ FISH positive) corresponding to 10%, a lower figure than the reported by other studies. ConclusionThe frequency of the HER 2 overexpression in Chile is lower than the series published in other countries, but similar to the Latin-American series.