HPV prevalence in the different subsites of the oropharynx.

Abstract

6037 Background: Oropharyngeal cancer patients are often reported as one group in articles and studies regardless that within the subsites of the oropharynx, there are differences regarding clinical features, treatment and HPV prevalence. To investigate these differences, we wanted to further analyze HPV prevalence in the different subsites of the oropharynx. Methods: We identified all patients diagnosed with oropharyngeal cancer in Stockholm County, Sweden, between 2000 and 2007, using the Swedish Cancer Registry, a registry unique in its reliability. Using the ICD 10 codes C01.9 (base of tongue cancer), C09.0-C09.9 (tonsillar cancer) and C10.0-C10.9 (oropharyngeal cancer) and C50.1-C50.8 (cancer of the soft palate). The two last subsites were grouped together into the group Other Oropharyngeal Cancer (OOC). We retrieved pre-treatment biopsies and tested for HPV-DNA using PCR, both with general primers and HPV16 specific primers. Results: We identified 474 patients diagnosed with oropharyngeal cancer in Stockholm County, Sweden between 2000 and 2007; 290 diagnosed with tonsillar cancer, 109 diagnosed with base of tongue cancer and 75 diagnosed with other oropharyngeal cancer. Of these 474 patients, pre-treatment biopsies for HPV-testing were available for 400 patients (236, 95 and 69, respectively). In the tonsillar cancer group, 185 biopsies were HPV-DNA-positive (79%), in the base of tongue cancer group 71 (75%) and in the other oropharyngeal cancer group 17 were positive (25%) Conclusions: Tonsillar and base of tongue cancer share some similarities and HPV prevalence is similarly high in both groups. Other oropharyngeal cancer (OOC) does not share the high HPV-prevalence and it would then be preferred that the sub-sites of the oropharynx are reported separately.