Concordance of HER2 and its related molecules between primary and paired liver metastatic sites in gastric cancer.

Abstract

4108 Background: Trastuzumab is the 1st molecular targeting drug in HER2-positive advanced gastric cancer that has been shown to confer overall survival benefit adding to chemotherapy. In breast cancer it has been already used long time, it is known that there are the discordance of its target; HER2 between primary and metastatic site. Although molecular targeting drugs as Trastuzumab are expected to control the metastatic disease, molecular status is usually evaluated in the primary site because metastatic sites are difficult to biopsy. In this study we attempted to compare HER2 and its related molecular status, which have interaction each together, between primary and paired liver metastatic sites in gastric cancer. Methods: Total 58 consecutive cases with gastric cancer who underwent surgical resection of primary site and synchronous or metachronous liver metastasis were examined. HER2, EGFR, c-MET and IGF-1R status were evaluated by immunohistochemistry(IHC) in primary and paired liver metastasis. HER2 expression by IHC using HercepTest (DAKO) were assessed according to Gastric Cancer Scoring System. On the other molecular expression by IHC, positive expression was defined as 25% or more staining with intensity 2 or 3+. We analyzed the concordance of their expression in both sites. Results: The patient cohort consists predominantly of male (78%), with Lauren’s diffuse (37%) and intestinal tumors (62%). Fifty three percent of cases were synchronous liver metastasis. The positive rate of primary and paired liver metastatic sites were 10.3%, 8.6% in HER2, 1.7%, 5.1% in EGFR, 44.8%, 31.0% in c-MET and 31.0%, 29.3% in IGF-1R. The concordance between primary and paired liver metastatic sites were 91.3%, 93.1%, 75.8%, and 70.6%, respectively. Conclusions: Our data suggested that in HER2 and EGFR the concordance between primary and metastatic site were high, other hands the concordance of c-MET and IGF-1R were relatively low. It might be necessary to rebiopsy to estimate the expression of c-MET and IGF-1R in gastric cancer.