The Epidemic of Human Papillomavirus and Oropharyngeal Cancer in a Canadian Population

Background: Sexually transmitted infection with the human papillomavirus (HPV) is responsible for a significant burden of human cancers involving the cervix, anogenital tract, and oropharynx. Studies in the United States and Europe have demonstrated an alarming increase in the frequency of HPV-positive oropharyngeal cancer, but the same direct evidence does not exist in Canada. Methods: Using the London Health Sciences Centre pathology database, we identified tonsillar cancers diagnosed between 1993 and 2011. Real-time polymerase chain reaction was then used on pre-treatment primary-site biopsy samples to test for DNA from the high-risk HPV types 16 and 18. The study cohort was divided into three time periods: 1993–1999, 2000–2005, and 2006–2011. Results: Of 160 tumour samples identified, 91 (57%) were positive for HPV 16. The total number of tonsillar cancers significantly increased from 1993–1999 to 2006–2011 (32 vs. 68), and the proportion of cases that were HPV-positive substantially increased (25% vs. 62%, p < 0.002). Those changes were associated with a marked improvement in 5-year overall survival (39% in 1993–1999 vs. 84% in 2006–2011, p < 0.001). When all factors were included in a multivariable model, only HPV status predicted treatment outcome. Interpretation: The present study is the first to provide direct evidence that HPV-related oropharyngeal cancer is increasing in incidence in a Canadian population. Given the long lag time between HPV infection and clinically apparent malignancy, oropharyngeal cancer will be a significant clinical problem for the foreseeable future despite vaccination efforts.