Role of Enteral Immunonutrition in Patients Undergoing Surgery for Gastric Cancer: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Gastric cancer (GC) is one of the most common upper gastrointestinal malignancies. Surgical resection remains the mainstay of curative treatment for GC. Enteral immunonutrition (EIN) has been increasingly used to enhance host immunity and relieve inflammatory response of patients undergoing surgery for GC; however, conclusions across studies still remain unclear. We aimed to evaluate the effects of EIN for such patients. We searched some electronic databases including PubMed, EBSCO-Medline, Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE to identify any latent studies which investigated the effects of EIN compared with standard EN on GC patients who undergoing surgery until the end of December 30, 2014. Relative risk (RR), mean difference (MD), or standard mean difference (SMD) with 95% confidence interval (CI) were calculated and we also assessed heterogeneity by using Cochrane Q and I(2) statistic combined with corresponding P-value. We included 9 eligible studies which included 785 patients eventually. The meta-analysis results shown that EIN increased level of IgA (MD, 0.31; 95% CI, 0.12–0.51), IgG (MD, 1.5; 95% CI, 0.73–2.28), IgM (MD, 0.22; 95% CI, 0.06–0.39), CD4(+) (SMD, 0.81; 95% CI, 0.53–1.09), CD3(+) (SMD, 0.68; 95% CI, 0.21–1.15), CD4(+)/CD8(+) ratio (MD, 0.56; 95% CI, 0.12–1.01), and NK cell (MD, 2.35; 95% CI, 0.66–4.05); decreased IL-6 (MD, −98.22; 95% CI, −156.16 to −40.28) and TNF-α (MD, −118.29; 95% CI, −162.00 to −74.58), but not improve remained outcomes of interest involving postoperative complications, length of hospitalization, serum total protein, and CD8(+). Descriptive analysis suggested that EIN also increased the concentration of IL-2 but not CRP. Impact on lymphocytes remains inconsistent. EIN is effective for enhancing host immunity and relieving the inflammatory response in GC patients undergoing gastrectomy, but clinical outcomes cannot be benefit from it. Heterogeneity caused by different compositions and timing of administration of EIN regimes and not enough sample size and number of eligible studies in most of sensitive analyses with subgroup analysis may impaired the power of our study, and thus some large-scale and well-designed studies are warranted to further establish effects.