# Perioperative Nutritional Support: A Review of Current Literature
## 5 Perioperative Nutritional Support in Oncological Pathology
### Gastrointestinal Cancer  
The evidence of perioperative nutritional support in cancer patients has been especially studied in gastrointestinal tumors, and the recommendations of the current guidelines can also be applied to non-oncological gastrointestinal surgery. A total of 65% of patients who undergo surgery for these tumors meet the criteria for malnutrition due to both tumor cachexia and decreased caloric intake [71]. In patients with gastric cancer, several perioperative nutritional parameters have been described as independent prognostic factors [72]. In a study of 800 patients with gastric cancer who underwent gastrectomy and were at high risk of malnutrition, the group with nutritional support for at least 10 days had fewer infections than the group with poor or no support [73]. In addition, early oral nutrition decreases length of hospital stay when compared to its delayed onset, with no increase in complications compared to those receiving parenteral nutrition [74]. Beyond surgical complications, the loss of weight and muscle mass in this period affects the toxicity of adjuvant treatment, which has implications for the continuity of these therapies, disease recurrence and survival [75]. Regarding the use of Oral Nutritional Supplements (ONS) in the perioperative period, their benefit may be diminished by the low compliance in this group of patients after the reduction of the size of their stomach [75]. The use of immunonutrition formulas in patients with gastric cancer who are going to undergo gastrectomy is controversial. Therefore, in 2016, [PERSON] et al. [76] performed a systematic evaluation with 9 randomized clinical trials, concluding that omega-3 (n-3) polyunsaturated fatty acids (PUFA)-rich formulas significantly reduced postoperative infectious complications as well as length of hospital stay and duration of systemic inflammatory response syndrome, especially in malnourished patients. In esophageal tumors, there are also studies showing that weight loss and/or skeletal and muscle mass loss are associated with worse treatment outcomes and increased recurrence at 5 years [77; 78]. On the other hand, artificial nutrition has been associated with fewer post-surgical complications after esophagectomy [79]. As with gastrocnemius, early oral nutrition is recommended, as there are safety data available [80]. Few studies have evaluated the role of eicosapentaenoic acid (EPA)-based immunonutrient formulations in preventing this loss, with discordant results [75]. Another issue under discussion is the role of vitamin D in patients with esophageal cancer undergoing esophagectomy, since two studies have shown that vitamin D supplementation or adequate vitamin D levels may be associated with a reduction in markers of alveolar edema and post-surgical lung injury [81; 82]. In colorectal cancer (CRC), nutritional treatment on the first postoperative day was an independent predictor of survival at 5 years after surgery in the study by [PERSON] et al. [83]. There is also a growing interest in the role of immunonutrition and prebiotics, since alterations in the microbiota have been shown to be a risk factor for this type of tumor [84]. In 2011, a phase III clinical trial demonstrated that preoperative administration of prebiotics promoted recovery of intestinal function and improved both immune system function and nutritional status [85]. In 2018, another study demonstrated that the use of prebiotics improved both pre- and postoperative immunological parameters even if it did not alter the species of bacteria present in the microbiota [86]. In the same year, a meta-analysis evaluating immunonutrition in patients with CRC undergoing surgery was also published [87]. It showed that applying this type of formula via enteral nutrition reduced length of hospital stay and infectious complications, while parenteral nutrition reduced length of hospital stay and improved immunological parameters.