Abstract 4071
Background
Test for the human epidermal growth factor receptor 2 (HER2) expression is an essential step to select gastric cancer patients for HER2 molecular targeted therapy. Peritoneal carcinomatosis with ascites is the most common manifestation of gastric cancer metastases, prevalence upto 40% in previous reports. The aim of this study is to compare the HER2 expression status in primary gastric adenocarcinoma and paired cell block of malignant ascites.
Methods
Forty-five patients with evaluable tissue samples of both primary gastric lesion and ascites cell block were enrolled. HER2 expression status was evaluated by immunohistochemistry (IHC) in primary tumor and in paired cell blocks of ascites which was confirmed by the qualified pathologist.
Results
HER2 expression was detected in 16 patients (35.6%) from primary gastric adenocarcinoma tissue and in 10 (22.2%) from ascites cell block. HER2 overexpression defined by IHC 3+ was observed in 2 (4.4%) and 3(6.7%) of primary lesion and ascites samples, respectively. However the HER2 status of primary tumor and ascites cell block showed discordance in all of those patients with HER2 overexpression. Patients with HER2 overexpression in primary gastric tissue showed HER2 negativity in ascites cell block, and vise versa. Of the 14 patients whom with two or more serial ascites samples, the HER2 IHC score differences between the samples were observed in five patients (35.7%).
Conclusions
Incidence of HER2 overexpression was slightly lower than previous reports in primary gastric tumor and metastatic ascites samples in this study. Discordances of HER2 expression status between the primary gastric adenocarcinoma and ascites cell block or between serially sampled ascites were observed in a significant proportion of the patients (20%). HER2 testing from both primary tumor and ascites cell block and from serial ascites sample could increase the sensitivity of HER2 overexpression detection, and assist to select adequate patients for HER2 molecular targeted therapy.
Clinical trial identification
Legal entity responsible for the study
Chungbuk National University Hospital.
Funding
Chungbuk National University Hospital.
Editorial Acknowledgement
Disclosure
All authors have declared no conflicts of interest.