1. Department of Radiation Oncology; Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in Southern China, Collaborative Innovation Center for Cancer Medicine; 651 Dong Feng Road East Guangzhou 510060 Guangdong P. R. China
2. Department of Oncology; Shunde Hospital of Southern Medical University; Foshan 528399 Guangdong P. R. China
3. Department of Radiation Oncology; Hainan General Hospital; Haikou 570100 Hainan P. R. China
4. Department of Radiation Oncology, National Cancer Center/Cancer Hospital & Shenzhen Hospital; Chinese Academy of Medical Sciences and Peking Union Medical College; Shenzhen 518116 Guangdong P. R. China