CD4 and gastric cancer: Perioperative immune indexes of patients with gastric cancer treated with enteral nutrition with ω-3 polyunsaturated fatty acid preparations during surgery (including IgG [WMD = 1.14, P < 0.0001], IgA [WMD = 0.36, P = 0.0008], IgM [WMD = 0.22, P < 0.0001], CD4 [WMD =6.81, P = 0.0001] and CD4/CD8 [WMD = 0.46, P = 0.002]) were superior to conventional EN preparations.