The incidence of oropharyngeal squamous cell carcinoma (OPSCC) is increasing among elderly adults in the United States [1]. The purpose of this study was to examine whether this recent rise in OPSCC among older age cohorts is due to increasing prevalence of human papillomavirus (HPV)-positive tumor status among elderly adults with OPSCC, and to determine whether HPV-positive tumor status continues to confer improved survival among older age cohorts.
This was a retrospective, multi-institutional study of OPSCCs diagnosed from 1995-2013. HPV tumor status was determined using immunohistochemistry for p16 overexpression and in-situ hybridization for HPV16 DNA and high-risk E6/E7 mRNA. Patient age at diagnosis, HPV tumor status, and calendar periods were compared. Survival was analyzed using Kaplan-Meier method and Cox Proportional Hazards models.
There were 240 patients with OPSCC included in this analysis, of which 124 (52%) were HPV-positive. Between 1995-2013, median age increased among HPV-positive OPSCCs (ptrend=0.05), but not among HPV-negative OPSCCs (1995-2013 ptrend=0.86). The median age of HPV-positive OPSCC patients increased from 43.5 years (interquartile range [IQR] 52-60.5) in 1995-2000 to 52 years (IQR 56-53) in 2007-2013. Among patients ≥65 years old, the proportion of OPSCCs that were HPV-positive increased from 29% (5/17) in 1995-2000 to 52% (11/21) in 2001-2006, then 60% (12/20) in 2007-2013 (ptrend=0.07). This was similar to the increase noted among patients 55-64 years old (24% [5/12] in 1995-2000 to 58% [18/31] 2007-2013, ptrend=0.03). Among older age cohorts, HPV-positive tumor status was associated with significantly improved overall survival compared with HPV-negative tumor status (>65 year old: HR=0.56, 95% CI=0.29-1.10; >60 year old HR=0.37 95%CI=0.20-0.67). The association of HPV tumor status with improved overall survival after OPSCC diagnosis was not significantly attenuated with increasing patient age (p=0.56 for interaction of age and HPV status).
The median age at diagnosis of HPV-OPSCC is increasing as the proportion of OPSCCs caused by HPV rises among older age cohorts. The favorable survival conferred by HPV-positive tumor status is not modified by age.
[1] Zumsteg Z S, Cook-Wiens G, Yoshida E, Shiao S L, Lee N Y, Mita A, Jeon C, Goodman M T and Ho A S. “Incidence of Oropharyngeal Cancer Among Elderly Patients in the United States.” JAMA Oncol. 2016;2(12):1617-1623.