[1] Goethe Univ Frankfurt, Dept Radiat Oncol, Frankfurt, Germany
[2] Goethe Univ Frankfurt, Dr Senckenberg Inst Pathol, Frankfurt, Germany
[3] Goethe Univ Frankfurt, Dept Dermatol, Frankfurt, Germany
[4] Univ Cologne, Natl Reference Ctr Papilloma & Polyomaviruses, Inst Virol, Cologne, Germany
[5] Univ Hosp Zurich, Dept Radiat Oncol, Zurich, Switzerland