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