Prognostic significance of HPV and p16 status in patients with oropharyngeal cancer treated on a large international phase III trial

6004 Background: Previous studies have reported that in patients with oropharyngeal cancer (OPC) the presence of human papilloma virus (HPV) is associated with an improved prognosis. We sought to determine the prognostic importance of HPV and p16 in patients with OPC treated with concurrent chemoradiation on a large international phase III trial. Methods: Patients with previously untreated Stage III or IV head and neck squamous cell cancer were randomized to receive definitive radiotherapy concurrently with either cisplatin or cisplatin plus tirapazamine. In this substudy, analyses were restricted to patients with OPC who received > 60 Gy and did not have major radiation deviations predicted to impact on tumor control. HPV 16/18 were detected by in situ hybridization and scored as detected or undetected. p16 was detected by immunohistochemistry. Nuclear and cytoplasmic staining intensity of tumor cells was scored as grade 0–3, with grade 2 and 3 called positive. Log rank and Cox regression used for surviv...