1 Division of Head and Neck Surgery, Saitama Cancer Center Hospital, Saitama, Japan Division of Head and Neck Surgery, National Cancer Center Hospital East, Chiba, Japan wataoka@cancer-c.pref.saitama.jp.
2 Division of Head and Neck Surgery, National Cancer Center Hospital East, Chiba, Japan.
3 Department of Otolaryngology, Fukushima Medical University, Fukushima, Japan.