1. Department of Radiation Oncology, Osaka University Graduate School of Medicine, Osaka, Japan
2. Department of Radiation Oncology, Osaka General Medical Center, Osaka, Japan
3. Department of Radiation Oncology, Saito Yukoukai Hospital, Osaka, Japan
4. Department of Otorhinolaryngology-Head and Neck surgery, Osaka General Medical Center, Osaka, Japan
5. Department of Otorhinolaryngology-Head and Neck surgery, Osaka University Graduate School of Medicine, Osaka, Japan