# Perioperative Nutritional Support: A Review of Current Literature
## 5 Perioperative Nutritional Support in Oncological Pathology  
One of the pathologies in which the role of perioperative nutritional support has been most studied is cancer. Due to the increased catabolism that occurs in this group of diseases, cancer patients have a high prevalence of malnutrition, which has been shown to have a great impact on their survival [43]. This is especially relevant when facing the different treatments they must undergo, including surgery [44]. Severe malnutrition is an independent risk factor for increased postoperative morbidity and mortality as well as longer length of hospital stay and higher cost in cancer patients [45]. Finally, it should be noted that the perioperative period has been shown to be critical in determining the risk of post-surgery metastasis, although there are no studies to date that evaluate the role of nutritional support in this regard [46]. When evaluating perioperative support in cancer patients, we must first consider which patients can benefit from it. In this regard, there are studies that support nutritional support only in patients with moderate or severe malnutrition or those at risk of not receiving adequate oral nutrition for at least 7-14 days after surgery [47]. This is because studies of malnourished patients have shown that nutritional support leads to a reduction in surgical complications, including infections [48; 49; 50]; whereas in studies in which all cancer patients were treated regardless of nutritional status and risk, well-nourished patients treated with parenteral nutrition had an increased risk of infections while malnourished patients had an overall benefit [51]. Studies comparing patients with and without perioperative nutritional support including all cancer patients also showed no benefit [52]. To elucidate who should be treated, it is important for hospitals to include nutritional screening in cancer patients who are going to undergo surgery. In this regard, studies have shown that there is a high percentage of surgeons who believe that there are data to support the optimization of preoperative nutritional status to reduce complications. However, in the US, only 1 in 5 hospitals perform nutritional screening of patients undergoing oncologic/gastrointestinal surgery and only 20% of these patients receive some type of nutritional supplementation in the pre- or postoperative period [36]. Similar results were obtained in 2021 in a UK study of anesthesiologists: although 91.7% of respondents agreed that perioperative nutrition improved quality of life after surgery, 49.6% acknowledged that they did not feel prepared to identify and manage patients in need of it [53]. Regarding the type of nutritional support to be used, the ESPEN recommends that oncology patients should also follow the ERAS guidelines [54], prioritizing the enteral nutrition. Enteral nutrition has been associated with improvements in nitrogen balance and weight gain in cancer patients [55]. Although parenteral nutrition (PN) has also demonstrated these benefits, weight gain with this type of support is due to an increase in fat [56]. On the other hand, there are studies in which PN has been associated with a higher incidence of infections and surgical complications and increased cost in oncology patients [57; 58; 59; 60]. However, although no benefit has been demonstrated over general nutrition, there are studies that show a benefit over the use of perioperative fluid therapy in patients in whom the enteral route is not available [57; 61]. On the other hand, there is controversy about the role of PN in increasing tumor proliferation, demonstrated in murine models [62], but with discordant results and with little clinical relevance in humans [63; 64]. The role of immunonutrition in surgical oncology patients is also relevant. In 2009, the ASPEN guideline for nutritional support during anti-cancer treatments in adults [51] recommended the use of immunonutrients (specifically formulas with omega-3 acids, arginine and RNA) in cancer patients undergoing surgical treatment.