Objectives/hypothesis: To examine demographic, histologic, and survival trends of oral cavity and oropharyngeal (OC/OP) squamous cell carcinoma (SCCA) patients over the past 3 decades. To test the hypothesis that decreased histologic differentiation and increased disease-specific survival is related to a decline in smoking rates and an increased percentage of human papillomavirus (HPV)-related tumors.
Study design: Retrospective cohort analysis was done using the Surveillance, Epidemiology, and End-Results (SEER) database of the national cancer institute.
Methods: SEER data were used to design seven cohorts: 1975-1979, 1980-1984, 1985-1989, 1990-1994, 1995-1999, 2000-2004, and 2005-2006. Incidence rates, histologic tumor grade. and 5-year survival rates were analyzed over time. Further subgroup analysis was performed according to subsite, age, gender, and stage.
Results: In both OC and OP, well-differentiated (grade I) tumors decreased significantly over time, from 33% to 16% between 1975 and 2006 (P < .001). In contrast, poorly differentiated tumors (grade III) significantly increased from 23% to 34% (P < .001). Over time, 5-year survival rates of less differentiated tumors improved 57%, whereas survival of well-differentiated tumors improved only 15.5%. Tonsil, posterior oropharynx and tongue subsites showed the greatest improvement in survival over time.
Conclusions: Comprehensive population-based analysis of oral cavity and oropharyngeal carcinoma from 1975 to 2006 demonstrated significant trends toward decreased tumor differentiation and increased survival over time. These findings support the influence of HPV in OC/OP carcinoma and may have implications for treatment, prognosis, and possibly prevention.