1. Department of Oncology, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
2. Department of Internal Medicine, The First Hospital, Tsinghua University, Beijing 100016, China
3. Department of Health Statistics, School of Public Health, Shanxi Medical University, Taiyuan 030001, China
4. Beijing Key Laboratory for Precancerous Lesion of Digestive Diseases, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
5. Beijing Digestive Diseases Center, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China