1Department of Radiation Oncology, Hanyang University Hospital, Seoul, Korea
2Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea
3Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea
4Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
5Department of Radiation Oncology, Asan Medical Center, Seoul, Korea
6Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
7Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Korea
8Department of Radiation Oncology, Proton Therapy Center, National Cancer Center, Goyang, Korea
9Department of Radiation Oncology, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, Korea
10Department of Radiation Oncology, Ewha Womans University School of Medicine, Seoul, Korea
11Department of Radiation Oncology, Ewha Womans University Mokdong Hospital, Seoul, Korea
12Department of Radiation Oncology, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Korea
13Department of Radiation Oncology, Gyeongsang National University Hospital, Gyeongsang National University School of Medicine, Jinju, Korea
14Department of Radiation Oncology, Chonbuk National University Hospital, Jeonju, Korea
15Department of Radiation Oncology, Seoul Metropolitan Government–Seoul National University Boramae Medical Center, Seoul, Korea