1. Department of Epidemiology and Health Statistics, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University , Fuzhou, Fujian, P. R. China
2. College of Integrated Chinese and Western Medicine, Fujian University of Traditional Chinese Medicine , Fuzhou, Fujian, P. R. China
3. Key Laboratory of Gastrointestinal Cancer, Ministry of Education, Fujian Medical University , Fuzhou, Fujian, P. R. China