1. Department of Otolaryngology-Head and Neck Surgery; Hokkaido University Graduate School of Medicine; Sapporo Japan
2. Division of Head and Neck Surgery; National Cancer Center Hospital East; Kashiwa Japan
3. Division of Head and Neck Surgery; Miyagi Cancer Center; Sendai Japan
4. Department of Otolaryngology-Head and Neck Surgery; Tohoku University School of Medicine; Sendai Japan
5. Department of Head and Neck Oncology, Cancer Institute Hospital; Japanese Foundation for Cancer Research; Tokyo Japan
6. Department of Otorhinolaryngology-Head and Neck Surgery; National Shikoku Cancer Center; Matsuyama Japan
7. Department of Head and Neck Surgery; Aichi Cancer Center; Nagoya Japan
8. Department of Head and Neck Surgery; Shizuoka Cancer Center; Shizuoka Japan
9. Department of Otolaryngology; Nagoya University Graduate School of Medicine; Nagoya Japan
10. Department of Head and Neck Surgery; Hyogo Cancer Center; Akashi Japan
11. Department of Otolaryngology; Tokai University; Isehara Japan
12. Department of Otolaryngology; Fukushima Medical University; Fukushima Japan
13. Department of Otolaryngology-Head and Neck Surgery; Osaka Medical Center for Cancer and Cardiovascular Diseases; Osaka Japan
14. Department of Otorhinolaryngology; National Tokyo Medical Center; Tokyo Japan