Increasing prevalence of human papillomavirus-positive oropharyngeal cancers among older adults.

BACKGROUND: The incidence of oropharyngeal squamous cell carcinoma (OPSCC) is increasing among older adults. It is unknown whether these trends can be explained by human papillomavirus (HPV) and whether HPV-related tumors remain associated with an improved prognosis among older patients. METHODS: In a retrospective study of OPSCCs diagnosed from 1995 to 2013 at 2 National Comprehensive Cancer Network-designated cancer centers, p16 immunohistochemistry and in situ hybridization (ISH) for HPV-16, high-risk DNA, and/or E6/E7 RNA were performed. The median age at diagnosis was compared by p16 and ISH tumor status. Trends in age were analyzed with nonparametric trends. Survival was analyzed with the Kaplan-Meier method and Cox proportional hazards models. RESULTS: Among 239 patients, 144 (60%) were p16-positive. During 1998-2013, the median age increased among p16-positive patients (P(trend) = .01) but not among p16-negative patients (P(trend) = .71). The median age of p16-positive patients increased from 53 years (interquartile range [IQR] in 1995-2000, 45-65 years) to 58 years (IQR for 2001-2013, 53-64 years). Among patients >/= 65 years old, the proportion of OPSCCs that were p16-positive increased from 41% during 1995-2000 to 75% during 2007-2013 (P(trend) = .04). Among all age groups, including older patients, a p16-positive tumor status conferred improved overall survival in comparison with a p16-negative status. CONCLUSIONS: The median age at diagnosis for HPV-related OPSCC is increasing as the proportion of OPSCCs caused by HPV rises among older adults. The favorable survival conferred by an HPV-positive tumor status persists in older adults. Cancer 2018;124:2993-9. (c) 2018 American Cancer Society.