[1] Velindre Canc Ctr, Dept Clin Oncol, Cardiff, S Glam, Wales
[2] Cardiff Univ, HPV Res Grp, Sch Med, Cardiff CF10 3AX, S Glam, Wales
[3] Newcastle Univ, Dept Otolaryngol Head & Neck Surg, Newcastle Upon Tyne Hosp NHS Trust, Northern Inst Canc Res, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[4] Univ Wales Hosp, Dept Otolaryngol Head & Neck Surg, Cardiff CF4 4XW, S Glam, Wales
[5] Guys & St Thomas NHS Fdn Trust, London, England
[6] Univ Coll London Hosp, Dept Histopathol, London, England
[7] Newcastle Univ, Ctr Oral Hlth Res, Sch Dent Sci, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[8] Kings Coll London Dent Inst, London, England