1. Department of Head and Neck Medical Oncology, National Cancer Center Hospital East, Kashiwa, Chiba 277-8577, Japan
2. Advanced Clinical Research of Cancer, Juntendo University Graduate School of Medicine, Bunkyo-Ku, Tokyo 113-8421, Japan
3. Division of Pathology, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, Kashiwa, Chiba 277-8577, Japan
4. Department of Digestive Endoscopy, National Cancer Center Hospital East, Kashiwa, Chiba 277-8577, Japan
5. Biostatistics Division, Center for Research Administration and Support, National Cancer Center, Kashiwa, Chiba 277-8577, Japan
6. Head and Neck Surgery Division, National Cancer Center Hospital East, Kashiwa, Chiba 277-8577, Japan
7. National Cancer Center Hospital East, Kashiwa, Chiba 277-8577, Japan