1. Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea.
2. Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
3. Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Korea.
4. Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.
5. Department of Otolaryngology, Seoul National University College of Medicine, Seoul, Korea.
6. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.