Prognostic value of p16 expression irrespective of human papillomavirus status in patients with oropharyngeal carcinoma

Objective: In a previous study, we reported the value of p16 expression and alcohol consumption in oropharyngeal carcinoma in Japan.We nowreport the clinical significance of human papillomavirus status and p16 expression in oropharyngeal carcinoma in Japan. Methods: Over a 9-year period, a retrospective case comparison study of the pathology database was conducted at the University of Tokyo to identify tumor samples of oropharyngeal carcinoma. We performed immunohistochemistry for the p16 protein, in situ hybridization for human papillomavirus- deoxyribonucleic acid and polymerase chain reaction for the human papillomavirus-deoxyribonucleic acid oncogene E6 in oropharyngeal carcinoma in Japanese patients. We evaluated the human papillomavirus status in patients with oropharyngeal carcinoma to determine its prevalence and association with prognosis.We defined human papillomavirus(+) and human papillomavirus(-) oropharyngeal carcinoma cohorts as those with and without polymerase chain reaction for the human papillomavirus-deoxyribonucleic acid oncogene E6 or in situ hybridization-human papillomavirus. Results: In oropharyngeal carcinoma, the prevalences of p16(+)human papillomavirus(+), p16(+) human papillomavirus(-), p16(-)human papillomavirus(+) and p16(-)human papillomavirus(-) were 32% (48/150), 7% (10/150), 2% (3/150) and 59% (89/150), respectively. Low tobacco and alcohol consumption, tonsil or base of tongue localization, but not age, were associated with p16(+)human papillomavirus(+). Low alcohol consumption was associated with p16(+)human papillomavirus(-). There was a significant difference in overall survival between p16(+)human papillomavirus(-) and p16(-)human papillomavirus(-) (P = 0.03). In multivariate Cox regression models, p16 was the independent prognostic factor, regardless of human papillomavirus status. Conclusion: p16 expression was a reliable prognostic biomarker regardless of human papillomavirus status.