Effectiveness of preoperative oral nutritional supplements in colorectal cancer patients undergoing surgery: A systematic review and meta analysis

Summary: Background & aims: Poor nutritional status has been shown to have a detrimental effect on the prognosis of patients undergoing surgery. Oral nutritional supplements (ONS) are commonly used in the preoperative period to improve the nutritional status of patients. However, the impact of ONS on postoperative clinical outcomes remains controversial. This systematic review aims to evaluate the effectiveness of preoperative ONS on clinical outcomes of patients undergoing colorectal cancer surgery. Methods: Nine databases, including English databases (PubMed, Embase, the Cochrane Library, Web of Science, CINAHL) and Chinese databases (China National Knowledge Infrastructure (CNKI), Wanfang Data Knowledge Service Platform, China Science and Technology Journal Database, China Biology Medicine disc), were searched from their establishment to October 2022. The last search was conducted in June 2023, and the language was limited to Chinese and English. The secondary outcomes included wound infection, anastomotic leakage, and length of hospital stay. A meta-analysis was performed using RevMan 5.4 software. Results: Seven randomized controlled trials involving 737 subjects were included, 363 in the treatment group and 374 in the control group. All seven trials involved patients with colorectal cancer. Patients in the intervention group received ONS, while those in the control group received a conventional diet or an isoenergetic and isonitrogenous diet. The fixed effect model showed that the total incidence of postoperative complications in the intervention group was significantly lower than that in the control group [RR=0.83, 95%CI (0.70, 0.98), P=0.03, I2=29%, n=737]. However, there was no statistical significance in reducing wound infection, anastomotic leakage, or urinary tract infection. Conclusion: This study provides evidence that preoperative ONS can reduce the incidence of postoperative complications, but there is still a need for further research to support their routine use as preoperative nutritional support.