1. Cancer Center, The Second People's Hospital of Neijiang, Neijiang, Sichuan 641000, P.R. China
2. Department of Health Management Center, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, P.R. China
3. Department of Gastrointestinal Surgery, Harbin Medical University Cancer Hospital, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China