Association between prior smoking and the time between HPV16-E6 seroconversion and development of oropharyngeal squamous cell carcinoma

Background and aims: Human papillomavirus (HPV) type 16 E6 oncoprotein antibodies in peripheral blood are a strong marker of oropharyngeal squamous cell carcinoma (OPSCC). In a previous study, HPV16-E6 seroconversion was observed from 6 to 28 years before cancer diagnosis. In the present study, the serology measurements were complemented with DNA and RNA genotyping of HPV from cancer tissue from the same OPSCC patients. We aimed to refine estimates of timing of and age at HPV16-E6 seroconversion before HPV-driven OPSCC and to investigate their dependence on notable covariates such as tobacco use. Patients and methods: 307 OPSCC cases were identified from the prospective Janus Serum Bank Cohort in Norway enrolled from 1972 to 2004. Pre-diagnostic samples were analyzed for antibodies against proteins of HPV16 and other oncogenic HPV types by multiplex serology. Diagnostic formalin-fixed paraffin-embedded tumor blocks were obtained from different hospitals and HPV DNA and RNA genotyped by Multiplex Papillomavirus Genotyping and HPV type-specific E6*I RNA assays. Cancers positive for DNA and RNA of the same HPV type were regarded as HPV-driven . Information about smoking status was available from questionnaires. For every HPV16-driven cancer, an age and time interval for HPV16-E6 seroconversion was inferred and the Turnbull estimator for interval-censored data was applied. Results: Out of 242 OPSCC cases with a retrieved and successfully sectioned tumor block, 221 (83.7%) had a valid HPV DNA/RNA cancer tissue test. The proportion of OPSCC driven by HPV increased rapidly from 1990 (0%) to 2010 (over 60%). The majority of the HPV-driven OPSCC cases were caused by HPV16 (55.2% of all OPSCC cases), followed by HPV33 (5.4%). All patients developing HPV16-driven cancer within 10 years from blood draw were HPV16-E6 seropositive at blood draw. The estimated median age of HPV16-E6 seroconversion for HPV16 driven cancers was 43 years with an interquartile range (IQR) of 41-46, and the median time from seroconversion to HPV16-driven cancer was 16 years (IQR: 12-22). Current smokers had a much shorter time from seroconversion to cancer than former and never smokers (median of 14 vs 18 and 21 years). Conclusions: The high sensitivity and specificity of HPV16-E6 seropositivity makes it a promising early biomarker for HPV-driven OPSCC. HPV16-E6 seropositive individuals that were smokers at the time of blood draw developed HPV16-driven OPSCC 8 years earlier than seropositive individuals that never smoked, suggesting intensified follow-up of HPV16-E6 seropositive smokers. The age at HPV16-E6 seroconversion indicates that many cancer-causing HPV infections are acquired after mid-20s, with the implication that young adults would benefit from HPV vaccination for prevention against oropharyngeal cancer.