1. Department of Otolaryngology, Fukushima Medical University Hospital, Fukushima, Japan
2. Department of Medical Oncology and Hematology, Kobe University Hospital, Kobe, Japan
3. Kobe University Hospital Cancer Center, Kobe, Japan
4. Japan Clinical Oncology Group Data Center/Operations Office, National Cancer Center Hospital, Tokyo, Japan
5. Radiation Oncology, National Cancer Center Hospital East, Kashiwa, Japan
6. Department of Otolaryngology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
7. Asahi University Hospital, Department of Head and Neck Surgery and Otolaryngology, Gifu, Japan
8. Department of Head and Neck Surgery, Aichi Cancer Center, Nagoya, Japan
9. Department of Head and Neck Surgery, Hyogo Cancer Center, Akashi, Japan
10. Department of Head and Neck Surgery, Shikoku Cancer Center, Matsuyama, Japan
11. Division of Head and Neck Surgery, Miyagi Cancer Center, Natori, Japan
12. Division of Clinical Oncology, Shizuoka Cancer Center, Shizuoka, Japan
13. Department of Head and Neck Surgery, National Cancer Center Hospital East, Kashiwa, Japan
14. Department of Head and Neck Medical Oncology, National Cancer Center Hospital East, Kashiwa, Japan