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

Abstract

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 survival analyses. p values were 2-sided . Results: 384 out of 861 patients had OPC and met the eligibility criteria. Slides were available for HPV assay in 195 and for p16 in 186, and for both in 173. 54/195 (28%) were HPV positive, 107/186 (58%) were p16 positive. HPV pos tumors were associated with better 2-year overall survival (OS) (94 v 77%, p = 0.007) and better failure-free survival (FFS) (86 v 75%, p = 0.035) compared to HPV neg tumors. Similarly p16 pos tumors were associated with better 2-year OS (92 v 75%, p = 0.004) and FFS (87 v 72%, p = 0.003) compared to p16 neg . After adjustment for stage, Hb and ECOG PS, HPV pos had better OS than HPV neg (HR 0.29, p = 0.018), and p16 pos had better OS than p16 neg (HR 0.39, p = 0.013). When the HPV and p16 results were combined the relative HRs for OS were: HPVpos/p16pos 0.35 (45 patients, 26% of cases), HPVpos/p16neg 0 (3pts, 2%), HPVneg/p16pos 0.73 (58pts, 33%), HPVneg/p16neg 1.79 (67 pts, 39%). Conclusions: Our results confirm the prognostic significance of tumor HPV status in oropharyngeal cancer treated with chemoradiation, but also show that p16 identifies a larger group with an improved prognosis. The HPV neg/p16 pos population has a better prognosis compared to patients with HPV neg/p16 neg tumors. No significant financial relationships to disclose.