Human papillomavirus is more common in base of tongue than in mobile tongue cancer and is a favorable prognostic factor in base of tongue cancer patients

The frequency of human papilloma virus (HPV) and its influence on clinical outcome was analyzed retrospectively in pre-treatment paraffin embedded biopsies from 110 patients with tongue cancer. The presence of HPV DNA was examined in 85 mobile tongue tumors and 25 base of tongue tumors by a polymerase chain reaction (PCR) with 2 general primer pairs, GP5+/6+ and CPI/IIG. When HPV-DNA was found, HPV-type specific primers and direct sequencing were used for HPV sub-type verification. Twelve of 110 (10.9%) samples were HPV-positive; 9 for HPV-16, 1 for HPV-33, 1 for HPV-35 and 1 could not be analyzed because of shortage of DNA. HPV was significantly more common in base of tongue tumors (10/25, 40.0%) compared to tumors of the mobile tongue (2/85, 2.3%). The influence of HPV on clinical outcome in mobile tongue cancer could not be studied, due to that HPV was present in too few cases. Of the 19 patients with base of tongue cancer that were included in the survival analysis, however, 7 patients with HPV-positive base of tongue cancer had a significantly favorable 5-year survival rate compared to the 12 HPV-negative patients. In conclusion, HPV is significantly more common in base of tongue cancer than in mobile tongue cancer, and has a positive impact on disease-specific survival in patients with base of tongue cancer.