1. Department of Radiation Oncology, Sun Yat-sen University Cancer Center, Guangzhou, People's Republic of China
2. Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong, People's Republic of China
3. Guangdong Esophageal Cancer Research Institute, Guangzhou, Guangdong, People's Republic of China
4. Department of Statistical Science, School of Mathematics & Computational Science, Sun Yat-Sen University, Guangzhou, People's Republic of China
5. Department of Ophthalmology, University of Melbourne, Melbourne, Victoria, Australia
6. Department of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, Guangdong Province, People's Republic of China