1. Research Department, PLA Rocket Force Characteristic Medical Center, Beijing 100088, P.R. China
2. Department of Oncology, PLA Rocket Force Characteristic Medical Center, Beijing 100088, P.R. China
3. Health Management Division, PLA Rocket Force Characteristic Medical Center, Beijing 100088, P.R. China
4. Department of Endoscopy, PLA Rocket Force Characteristic Medical Center, Beijing 100088, P.R. China