OP195: HPV epidemic also in previously low prevalence regions: Data on tonsillar and base-of-tongue carcinomas from the northern Netherlands.

Purpose: HPV-associated cancer in the head-neck region has been reported at high frequencies in certain countries and is considered a separate entity. Since the prevalence of HPV positivity in oropharyngeal squamous cell carcinomas is currently not known in the Northern part of the Netherlands, the aim was to analyze HPV prevalence in oropharyngeal tumours treated at our centre. Material and methods: Based on the Dutch cancer registration, we collected clinical, pathological, and follow-up data and formalin-fixed paraffin embedded samples of a complete cohort of 125 tonsillar and base-of-tongue oropharyngeal tumours treated in our centre from 1997 to 2009. HPV testing was performed using an established algorithm of p16 immunohistochemistry, followed by HPV-PCR of the positive cases. HPV-BRISH was performed as extra control of p16 negative cases. Results: p16 staining could be assessed on 109 cases. 32/109 (29%) were p16+ of these 32 cases 21/32 (66%) were HPV-GP+, 16 cases were found HPV16+ and one HPV18+, three were HPV33+ and one HPV35+. HPV-BRISH showed 83/102 (81%) negativity and 19/102 (19%) positivity. BRISH had a sensitivity of 85% and a specificity of 98%, as only two p16- cases were positive for BRISH. HPV prevalence increased from 11% between 1997 and 2002, to 27% between 2003 and 2009. Conclusions: In the period 1997–2009, 19% of the tonsillar and base-of-tongue tumours in the Northern Netherlands was HPV+. This prevalence is lower than in other regions in the Netherlands (33%) and in Europe (40%). Remarkably, a large increase in prevalence was observed in the more recent years. The relative low incidence in our region might be due to the relative high percentage of smokers, associated with non-HPV related oropharyngeal tumours. Currently HPV testing of a series of 200 oral squamous cell carcinomas from our centre is in progress. [Copyright &y& Elsevier]