4029 Background: Cetuximab is an IgG1, chimerized, monoclonal antibody that binds specifically to the epidermal growth factor receptor. Cetuximab improves survival when combined with radiation for patients with locally advanced head and neck cancer. We evaluated the safety and efficacy of the addition of cetuximab to concurrent chemoradiation for patients with esophageal and gastric cancer. METHODS Patients with adenocarcinoma or squamous cell cancer of the esophagus or stomach without distant organ metastases were eligible. Patients with locally advanced disease from mediastinal, celiac, portal and gastric lymphadenopathy were eligible. Surgical resection was not required. Clinical complete response was defined as no tumor on postreatment endoscopic biopsy. Patients received cetuximab, 400mg/m2 week #1 then 250 mg/m2/week for 5 weeks, paclitaxel, 50 mg/m2/week, and carboplatin, AUC =2 weekly for 6 weeks, with concurrent 50.4 Gy radiation. RESULTS Thirty-seven patients have been entered. The median age was 61 (range of 30-87). Thirty-four have esophageal cancer and 3 have gastric cancer. Of the patients with esophageal cancer, twenty-five have adenocarcinoma and nine have squamous cell cancer. Thus far, 30 patients have completed treatment and are evaluable for toxicity. There have been no grade 4 non-hematologic toxicities and 1 pt had grade 4 neutropenia (3%). Six patients (20%) had grade 3 esophagitis. Other grade 3 toxicities included dehydration (n=5), rash (n=9), and paclitaxel/cetuximab hypersensitivity reactions (n=2). Eighteen of 27 patients (67%) have had clinical complete response. Seven pts out of 16 (43%) who have gone to surgery have had a pathologic CR. CONCLUSIONS Cetuximab can be safely administered with chemoradiation for patients with esophageal cancer. Consistent with the data in head and neck cancer, cetuximab increases cutaneous toxicity but does not increase mucositis/esophagitis when combined with chemoradiation. Further evaluation is ongoing. [Table: see text].