Epidemiology Division;
Hebei Cancer Institute;
Shijiazhuang 050011;
China;
Department of Endoscopy;
Hebei Tumor Hospital;
Shijiazhuang 050011;
China;
Department of Pathology;
Hebei Tumor Hospital;
Shijiazhuang 050011;
China;
Shexian Cancer Institute;
Shexian 056400;
China;