Response to cetuximab by ESCC PDXs directly correlate to EGFR overexpression.

e15078 Background: Esophageal squamous cell carcinoma (ESCC) is a deadly malignance prevalent in parts of China and no target therapy option. Cetuximab, approved for treating subset of metastatic colorectal carcinoma (mCRC) and head and neck squamous cell carcinoma (HNSCC), has yet to be tested on ESCC. Patient derived xenografts (PDXs) are known to mimic original patient diseases, and thus their drug response. Methods: We created a cohort of ESCC PDXs and conducted a preclinical mouse clinical trial (MCT) assessing antitumor activity of cetuximab by randomly enrolling a cohort of 16 ESCC PDXs. We analyzed the drug activity using endpoints of both ORR (objective response rate per traditional TGI, tumor growth inhibition%, and clinical RECIST criteria) and survival per PFS (progression free survival) and OS (overall survival). Finally, we also investigated associated biomarker predictive of response through genomic profiling of these PDXs. Results: 12/16subjects responded to cetuximab with ORR of 75% per 6...