1. Department of Otorhinolaryngology/Head and Neck Surgery University of Groningen, University Medical Center Groningen Groningen The Netherlands
2. Department of Pathology and Medical Biology University of Groningen, University Medical Center Groningen Groningen The Netherlands
3. Department of Epidemiology University of Groningen, University Medical Center Groningen Groningen The Netherlands
4. Department of Radiation Oncology University of Groningen, University Medical Center Groningen Groningen The Netherlands