Objectives/Hypothesis: To document the increasing incidence of oropharyngeal (OP) cancer and to provide evidence that this increase is caused by oncogenic human papilloma virus (HPV).
Study Design: Epidemiologic review and retrospective case series analysis.
Methods: We collected data from Colorado and the United States comparing the average annual age-adjusted incidence rates of OP and non-OP head and neck cancer between the periods 1980 to 1990 and 1991 to 2001. We obtained data on 72 patients with OP cancer from a single county in Colorado, from 1980 through 2004. HPV status was determined by DNA-polymerase chain reaction. We assessed disease-specific survival.
Results: The average annual age-adjusted incidence of OP cancer in males in Colorado increased from 2.54 per 100,000 to 3.47 (P < .05) or 36.6%, whereas the U.S. rate increased from 4.34 to 4.81 (P < .05) or 10.8%. The rates in females and the rates of non-OP head and neck cancer decreased. Of the 72 cases, 50 (69%) were positive for HPV subtype 16. The ratio of HPV-positive to HPV-negative cases prior to 1995 was 0.72 (8:11) but was 3.81 (42:11) afterward. Survival was positively affected by HPV status (hazard ratio of 0.15, confidence intervals 0.07–0.36, P < .001). Disease-specific survival was 83% in the HPV-positive patients and 15% in the HPV-negative group.
Conclusions: OP cancer incidence is increasing in Colorado males and to a lesser extent in U.S. males. The HPV-positive OP cancer cases were more frequent in the later years of the study. Disease-specific survival was much better in the HPV-positive patients, confirming that HPV testing defines a unique subset of patients. These findings suggest that HPV oncogenesis accounts for the increase in average annual age-adjusted incidence of OP cancer.