1. Department of Radiation Oncology, National Cancer Center/Cancer Hospital; Chinese Academy of Medical Sciences and Peking Union Medical College; Beijing 100021 P. R. China
2. Department of Thoracic Surgery, National Cancer Center/Cancer Hospital; Chinese Academy of Medical Sciences and Peking Union Medical College; Beijing 100021 P. R. China
3. Department of Medical Records, National Cancer Center/Cancer Hospital; Chinese Academy of Medical Sciences and Peking Union Medical College; Beijing 100021 P. R. China