Dynamic factors affecting HPV-attributable fraction for head and neck cancers.

Head and neck squamous cell carcinoma (HNSCC) is attributable to carcinogen and oncogenic virus exposure and rates are driven by the prevalence, intensity, and duration of exposures. Recent dramatic shifts in human behavior have resulted in substantial heterogeneity in HNSCC incidence trends over calendar time. For example, changes in sexual behavior during the 1900s likely increased exposure to oral human papillomavirus (HPV) infection and, consequently, rates of HPV-positive HNSCC. Shifting rate-ratios for HPV-positive versus negative HNSCC determine the HPV attributable fraction (AF), best measured by direct tumor testing for HPV DNA and RNA. Potential high efficacy of HPV vaccines against oral HPV infections will affect future incidence trends, depending on calendar time of introduction, male and female coverage, and herd protection. Accurate estimates of HPV AF for all cancers, including HNSCC, may inform HPV immunization policy and surveillance of effectiveness.