The Fraction Of Oropharyngeal Cancer Potentially Preventable By Controlling HPV Infection

LAM E. ²

Background:
Human papillomavirus (HPV) is a recognized cause of oropharyngeal squamous cell carcinoma (OPSCC). Strategy to prevent HPV infection including vaccination might decrease the incidence of OPSCC, but the impact is likely to vary between populations according to the fraction of HPV-associated cases.  This study analyzed this potentially preventable fraction in a southern Chinese (Hong Kong) population.

Methods: 207 patients which constituted 63.5% of all newly diagnosed OPSCC in Hong Kong during a 5-year period from 2005 to 2009, were examined for the presence of HPV DNA, and with E6/7 mRNA test to verify their oncogenic role.

Results: Molecular features of HPV involvement were found in 20.8% (43/207) of OPSCC. All HPV-positive cases were HPV-16, except one (HPV-18). HPV-associated OPSCC were significantly younger than HPV-negative cases (mean age: 59.8 vs 63.9 years, P=0.05). Multivariate analyses showed that HPV-associated OPSCC was more likely to occur in non-smokers (39.5 vs. 15.1%, OR: 2.89, P=0.05), non-drinkers (52.5 vs. 25.6%, OR: 2.72, P=0.04), originate from the palatine tonsils (83.7 vs. 53.7%, OR: 3.88, P=0.01), present with an early primary tumor (T1/2) (79.1 vs. 47.6%, OR: 3.81, P=0.004), and exhibit basaloid differentiation (33.3 vs. 7.3%, OR:19.74, P=0.006). HPV positivity was an independent predictor for better prognosis for both 5-years overall and 5-year disease-specific survivals (63.0% vs 29.7%, HR: 0.33, P<0.001, and 87.8% vs 42.6%, HR: 0.16, P<0.001, respectively).

Conclusion: The estimated age-standardized incidence of OPSCC in Hong Kong during the period 2005-2009 was 0.6/100,000/year, of which 20.8% were attributed to infection with high-risk HPV. The main risk factors for OPSCC in Hong Kong are still smoking and alcohol, whereas HPV attributed to a minor fraction.