Short-term evaluation of immune levels and nutritional values of EN versus PN in gastric cancer: a systematic review and a meta-analysis

Background: Postsurgical patients' oral feeding begins with clear fluids 1-3days after surgery. This might not be sufficiently nutritious to boost the host immune system and provide sufficient energy in gastric neoplastic patients to achieve the goal of enhanced recovery after surgery (ERAS). Our objective was to analyze the significance of early postoperative feeding tubes in boosting patients' immunity and decreasing incidence of overall complications and hospital stay in gastric cancer patients' post-gastrectomy. Methods: From January 2005 to May 24, 2019, PubMed and Cochrane databases were searched for studies involving enteral nutrition (EN) feeding tubes in comparison to parenteral nutrition (PN) in gastric cancer patients undergoing gastrectomy for gastric malignancies. Relative risk (RR), mean difference (MD), or standard mean difference (SMD) with 95% confidence interval (CI) were used to estimate the effect sizes, and heterogeneity was assessed by using Q and chi(2) statistic with their corresponding P values. All the analyses were performed with Review Manager 5.3 and SPSS version 22. Results: Nine randomized trials (n = 1437) and 5 retrospective studies (n = 421) comparing EN feeding tubes and PN were deemed eligible for the pooled analyses, with a categorized time frame of PODs >= 7 and PODs <7. Ratio of CD4+/CD8+ in EN feeding tubes was the only outcome of PODs <7, which showed significance (MD 0.22, 95% CI 0.18-0.25, P < 0.00001). Regarding other immune indicators, significant outcomes in favor of EN feeding tubes were measured on POD >= 7: CD3+ (SMD 1.71; 95% CI 0.70, 2.72; P = 0.0009), CD4+ (MD 5.84; 95% CI 4.19, 7.50; P < 0.00001), CD4+/CD8+ (MD 0.28; 95% CI 0.20; 0.36, P < 0.00001), NK cells (SMD 0.94; 95% CI 0.54, 1.30; P<0.00001), nutrition values, albumin (SMD 0.63; 95% CI 0.34, 0.91; P < 0.001), prealbumin (SMD 1.00; 95% CI 0.52, 1.48; P < 0.00001), and overall complications (risk ratio 0.73M-H; fixed; 95% CI 0.58, 0.92; P = 0.006). Conclusion: EN feeding tube support is an essential intervention to elevate patients' immunity, depress levels of inflammation, and reduce the risk of complications after gastrectomy for gastric cancer. Enteral nutrition improves the innate immune system and nutrition levels but has no marked significance on certain clinical outcomes. Also, EN reduces the duration of hospital stay and cost, significantly.