Clinical outcome according to tumor HER2 status and EGFR expression in advanced gastric cancer patients from the EXPAND study.

4021 Background: In the EXPAND study adding cetuximab to first-line capecitabine and cisplatin chemotherapy (CT) failed to improve clinical outcome in patients (pts) with advanced gastric or gastroesophageal junction cancer. This analysis assessed treatment outcome according to tumor HER2 status (a pre-defined subgroup) and EGFR expression in EXPAND study pts. Methods: Tumor HER2 status was determined primarily by immunohistochemistry (IHC), HER2 +ve tumors were IHC 3+ or IHC 2+ and fluorescence in situ hybridization (FISH) +ve. EGFR expression was assessed by IHC. A continuous scoring system (scale of 0–300) was used to determine the level of EGFR expression. Biomarker status was correlated with clinical outcome. Results: In both treatment arms, pts with HER2 +ve tumors (n=144) vs HER2 -ve tumors (n=535) had a longer median overall survival (OS): 13.3 (95% CI 10.9–15.5) vs 9.2 (95% CI 8.1–10.5) months in the CT + cetuximab arm and 14.0 (95% CI 11.3–17.1) vs 9.7 (95% CI 8.6–11.0) months in the CT arm, and...