Japan Clinical Oncology Group Data Center/Operations Office, Multi-institutional Clinical Trial Support Center, National Cancer Center, Tokyo. Department of Medical Oncology and Hematology, Kobe University Hospital, Hyogo nkiyota@med.kobe-u.ac.jp. Department of Head and Neck Medical Oncology, National Cancer Center Hospital East, Chiba. Department of Radiation Oncology, Aichi Cancer Center Hospital, Aichi. Department of Head and Neck Surgery, National Cancer Center Hospital East, Chiba. Department of Radiation Oncology, Juntendo University, Tokyo. Department of Otolaryngology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.