5529 Background: We previously reported results of a phase 2 study of concurrent cetuximab, a chimeric monoclonal antibody directed against the epidermal growth factor receptor, with cisplatin and RT in previously untreated patients with loco-regionally advanced SCCHN (ASCO 2003 A#1993). Preliminary efficacy data were encouraging, although toxicity was a concern. Subsequent prospective data indicate that cetuximab has significant clinical activity in patients with SCCHN both as a single agent, as well as a potentiator of RT, making the longer-term efficacy data from our prior study of particular interest. Methods: All patients received RT (70 Gy by concomitant boost) with planned concurrent cetuximab (400 mg/m2 IV x1, then 250 mg/m2 weekly during weeks 2–10) and cisplatin (100 mg/m2 IV during weeks 1 and 4). Surgery was reserved for relapsed/persistent disease. Primary endpoint was response rate. Secondary endpoints included toxicity, overall survival, progression-free survival, and quality of life (FACT-...