[1] Kobe City Med Ctr Gen Hosp, Dept Radiat Oncol, Kobe, Hyogo, Japan
[2] Kyoto Univ, Grad Sch Med, Dept Radiat Oncol & Image Appl Therapy, Kyoto, Japan
[3] Kyoto Univ, Grad Sch Med, Dept Otolaryngol Head & Neck Surg, Kyoto, Japan
[4] Kobe City Med Ctr Gen Hosp, Dept Otolaryngol Head & Neck Surg, Kobe, Hyogo, Japan