Human papillomavirus (HPV) is a strong risk factor for a subset of head and neck cancers (HNCs), primarily of the oropharynx (OPC). Sexual behaviours have been suggested as determinants of HPV infections in the oral cavity, but the evidence is inconsistent. Our objectives were to estimate the extent to which oral sex behaviour was associated with an increased risk of OPC, and how much of the association was mediated by oral HPV infection.
The Canadian site of the HeNCe Life study, an international hospital-based case-control study, recruited 389 incident HNC cases from four hospitals in the Montreal area. A total of 429 controls from outpatient clinics at the same hospitals as the cases were recruited and frequency-matched by age and gender. Life-course oral sex behaviors (including age at first oral sex and time since first oral sex) was collected by semi-structured interviews using a life-grid technique. Oral rinse and oral brush specimens, collected from both cases and controls, were analyzed for alpha HPV genotypes by PCR protocol. Mediation models using logistic regression were used to estimate the odds ratio (OR) and 95% confidence interval (CI) for the association between life course oral sex behaviors and risk of OPC, adjusting for age, sex, number of educational years, lifetime number of sexual partners, lifetime smoking and alcohol drinking.
A total of 188 OPC cases and 429 controls were included in the analyses. The majority were between 16 and 30 years old the first time having oral sex (63.8% and 55.2% for OPC and controls, respectively). HPV DNA was detected in 63.3% of cases and 14.2% of controls. HPV 16 genotype accounted for 76.5% and 16.4% of HPV positive cases and controls. Age at first oral sex practice was associated with OPC (adjusted OR=2.98; 95%CI 1.37-6.47). When stratified by HPV status, this association decreased (adjusted OR=1.09; 95%CI 0.25-4.71) only in the HPV-positive group. With respect to time since first oral sex, the adjusted ORs were 2.80 (95%CI 1.57-4.97) among all, and 1.04 (95%CI 0.31-3.50) in the HPV-positive group.
Oral sex behaviours were associated with an increased risk of OPC in Canadians, which appears to be mediated by oral HPV infection.