Effects of enteral nutrition and intestinal flora regulators on immune checkpoints in patients with digestive system tumors

Interventions: experimental group 1:Ruineng enteral nutritional emulsion;experimental group 2:Dongzeli probiotic powder;experimental group 3:Ruineng enteral nutritional emulsion and Dongzeli probiotic powder;blank control group:Nil Primary outcome(s): intestinal flora;Immune checkpoints;Evaluation of immune function Study Design: Non randomized control