[1] Natl Canc Ctr Hosp East, Dept Head & Neck Med Oncol, 6-5-1 Kashiwanoha, Kashiwa, Chiba 2778577, Japan
[2] Hokkaido Univ, Fac Med, Dept Otolaryngol Head & Neck Surg, Sapporo, Hokkaido, Japan
[3] Hokkaido Univ, Grad Sch Med, Sapporo, Hokkaido, Japan
[4] Kobe Univ Hosp, Canc Ctr, Dept Med Oncol & Hematol, Kobe, Hyogo, Japan
[5] Aichi Canc Ctr Hosp, Dept Head & Neck Surg, Nagoya, Aichi, Japan
[6] Tokyo Med & Dent Univ, Dept Head & Neck Surg, Bunkyo Ku, Tokyo, Japan
[7] Natl Canc Ctr Hosp East, Dept Head & Neck Surg, Kashiwa, Chiba, Japan
[8] Gifu Univ Hosp, Dept Otorhinolaryngol Head & Neck Surg, Gifu, Gifu, Japan
[9] Univ Tokyo, Dept Otolaryngol & Head & Neck Surg, Bunkyo Ku, Tokyo, Japan
[10] Yokohama City Univ, Sch Med, Dept Otorhinolaryngol Head & Neck Surg, Yokohama, Kanagawa, Japan
[11] Aichi Canc Ctr Hosp, Dept Radiat Oncol, Nagoya, Aichi, Japan
[12] Natl Canc Ctr Hosp East, Dept Radiat Oncol, Kashiwa, Chiba, Japan
[13] Hokkaido Univ, Fac Med, Dept Radiat Oncol, Sapporo, Hokkaido, Japan
[14] Canc Inst Hosp, Dept Med Oncol, Tokyo, Japan
[15] Kindai Univ, Dept Med Oncol, Fac Med, Sayama, Osaka, Japan
[16] Hyogo Canc Ctr, Dept Med Oncol, Akashi, Hyogo, Japan
[17] Shizuoka Canc Ctr, Div Gastrointestinal Oncol, Shizuoka, Japan