1. Division of Gastrointestinal Oncology, Shizuoka Cancer Center , 1007 Shimonagakubo, Nagaizumi-cho, Sunto-gun, Shizuoka, 411-8777 , Japan
2. Department of Radiation Oncology, Showa University School of Medicine , Tokyo , Japan
3. Department of Head and Neck, Esophageal Medical Oncology, National Cancer Center Hospital , Tokyo , Japan