1. Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, Guangdong, People's Republic of China
2. Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan, USA
3. Department of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, Guangdong, People's Republic of China
4. Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
5. Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China