1. Department of Otorhinolaryngology-Head and Neck Surgery, Turku University Hospital and University of Turku, Turku, Finland;
2. Department of Pathology, University of Turku and Turku University Hospital, Turku, Finland;
3. Department of Biostatistics, Turku University Hospital and University of Turku, Turku, Finland;
4. Department of Otorhinolaryngology-Head and Neck Surgery, Helsinki University Hospital and University of Helsinki, Helsinki, Finland;
5. Department of Oncology, Helsinki University Hospital and University of Helsinki, Helsinki, Finland;
6. Department of Oncology, Tampere University Hospital and University of Tampere, Tampere, Finland;
7. Department of Oncology, Oulu University Hospital and University of Oulu, Oulu, Finland;
8. Department of Oncology, Kuopio University Hospital and University of Kuopio, Kuopio, Finland;
9. Department of Otorhinolaryngology-Head and Neck Surgery, Oulu University Hospital and University of Oulu, Oulu, Finland;
10. Department of Oncology, Turku University Hospital and University of Turku, Turku, Finland