1. Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin 300070, P.R. China
2. Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong 250117, P.R. China
3. Department of Radiation Oncology, The Fourth People's Hospital of Jinan, Jinan, Shandong 250031, P.R. China
4. Department of Clinical Medicine, Weifang Medical University, Weifang, Shandong 261053, P.R. China