1. Division of Head and Neck; Cancer Institute Hospital; Tokyo Japan
2. Department of Head and Neck Surgery; Aichi Cancer Center; Aichi Japan
3. Department of Head and Neck Oncology; Saitama Medical University International Medical Center; Saitama Japan
4. Department of Surgery; Osaka Police Hospital; Osaka Japan
5. Department of Surgery; Kuma Hospital; Hyogo Japan
6. Head and Neck Surgery Division; National Cancer Center Hospital East; Chiba Japan
7. Department of Otorhinolaryngology-Head and Neck Surgery; Nara Medical University; Nara Japan
8. Department of Otolaryngology; Okayama Saiseikai General Hospital; Okayama Japan
9. Division of Otolaryngology; Head and Neck Surgery; Tottori University; Tottori Japan