Anti-EGFR treatment for EGFR-amplified gastroesophageal adenocarcinoma.

60Background: Gastroesophageal cancer (GEC) is a global health problem. Multiple phase III anti-EGFR trials of unselected metastatic GEC patients (pts) were negative, yet subset analyses suggested potential benefit in pts with EGFR amplification (amp). We sought to quantify the incidence of EGFR amp in metastatic/recurrent GEC pts compared to the locally advanced TCGA rate, treat them with EGFR antagonists, quantify response/duration, and assess for mechanisms of action and resistance (MOA, MOR). Methods: 106 stage IV GEC pts in any therapy (tx) line (L) were prospectively screened for EGFR amp between 9/1/14-8/31/16 at a single site using tumor next generation sequencing (NGS). EGFR amp samples were then assessed by FISH, immunohistochemistry (IHC) and mass spectroscopy (MS) to confirm. Pts received 1L ABT-806 (1/4) or 2L+ cetux (3/4) monoclonal anti-EGFR antibodies, in combination with chemotherapy if 1L or 2L (2/4), or as monotherapy for 3L+ (2/4). Pts were followed for response (ORR) and disease contr...