1. Department of Otolaryngology and Head and Neck Surgery Leiden University Medical Centre Leiden the Netherlands
2. Department of Head and Neck Surgery the Netherlands Cancer Institute Amsterdam the Netherlands
3. Dalla Lana School of Public Health University of Toronto Toronto Canada
4. Department of Medical Oncology and Hematology Princess Margaret Cancer Centre Toronto Canada
5. Department of Biostatistics University Health Network Toronto Canada
6. Institute of Biostatistics and Registry Research Brandenburg Medical School Theodor Fontane Neuruppin Germany