4534 Background: Cetuximab has demonstrated high efficacy in combination with irinotecan-based therapies in metastatic colorectal cancer and irinotecan/folinic acid/5-FU (IF) may be an effective alternative to cisplatin-based regimens in advanced gastric cancer. We therefore conducted a phase II AIO study to evaluate the tolerability and efficacy of cetuximab combined with IF as first-line treatment in patients with advanced gastric cancer. Methods: Patients (pts) were eligible with untreated adenocarcinoma of the stomach or oesophagogastric junction, with ECOG performance status (PS) < 2, measurable lesions and adequate organ functions. Pts received weekly cetuximab (first dose 400 mg/m2, subsequent doses 250 mg/m2) combined with chemotherapy consisting of irinotecan (80 mg/m2) plus 24 hours continuous infusion of sodium folinic acid (Na-FA: 200 mg/m2) and 5-FU (1500 mg/m2) on days 1, 8, 15, 22, 29 and 36 of a 50-day cycle. Treatment was continued until tumor progression and tumor assessments were performed every 2nd cycle. Results: Between Aug 2006 and Sep 2007, 49 pts were enrolled: 71% were males, median age was 63 years (range 33–77), median PS was 0 (65% pts), and 69% of pts and 31% of pts had gastric and oesophagogastric junction carcinomas, respectively. The median treatment time was 15.2 weeks (range 1.1–69.1). Grade 3/4 toxicities were diarrhoea (17% pts), skin reactions (13% pts), anorexia (9% pts), anaemia and fatigue (7%pts), allergic reactions, leucopoenia and neutropenia (4% pts each). Among 48 response-evaluable pts, the overall response rate (CR + PR) was 42% (CR 4%/PR 38%) and the tumour control rate was 73%. Median progression-free and overall survival times were 8.5 months (36.6 weeks; 95% CI 30.1; 48.1) and 16.6 months (71.1 weeks; 95% CI 50; 93.4), respectively. Conclusions: Cetuximab plus IF was well tolerated and encouraging survival data were observed. Cetuximab combined with chemotherapy in advanced or metastatic gastric cancer is under further investigation in an ongoing phase III trial. No significant financial relationships to disclose.