1. Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer/Key Laboratory of Cancer Prevention and Therapy, Tianjin Clinical Research Center for Cancer, Tianjin 300060, P.R. China
2. Department of Pathology, Medical College of Wisconsin Cancer Center, Milwaukee, WI 53226, USA
3. Department of Radiation Oncology, The First Hospital of Jilin University, Changchun, Jilin 130000, P.R. China
4. Department of Radiation Oncology, The People's Hospital of Wuhai Inner Mongolia, Wuhai, Inner Mongolia 016000, P.R. China