Malnutrition has a high incidence in malignant tumor patients and is present throughout the course of the disease. 40%~80% of tumor patients have malnutrition, and about 20% of malignant tumor patients die directly from malnutrition, which seriously affects patients’ treatment response, survival time and quality of life. Therefore, nutritional therapy should become the basic treatment for tumor patients. Consequences of malnutrition The effects of malnutrition on tumor patients include three levels: cellular, physiological and psychological. 1. At the cellular level, malnutrition weakens the body’s defense ability against pathogenic microorganisms, increases the risk of infection, delays wound healing, decreases intestinal nutrient absorption, and changes the function of multiple systems and organs such as blood clotting and kidney. 2, On the physiological level, malnutrition leads to the loss of muscles and fats such as whistling muscles and heart muscles, resulting in the atrophy of internal organs. 3. On the psychological level, malnutrition causes weakness, apathy, and fear of food, which in turn prolongs the recovery time of the disease. In short, malnutrition reduces the quality of life of patients, increases medical costs, weakens the therapeutic effect, increases the occurrence of complications, elevates the mortality rate and shortens the survival time. 1. Poor prognosis of patients Whether the weight of tumor patients decreases or not is an important parameter to determine the prognosis. Compared with static body mass index, the dynamic change of body weight is more meaningful. The survival time of patients with weight loss and malnutrition is significantly shorter than that of patients with stable weight and good nutrition. The chemotherapy response rate and physical status score of patients with weight loss and malnutrition are lower than those of patients with stable weight and good nutrition. 2. Low quality of life Malnourished tumor patients often suffer from physical dysfunction, fatigue, pain, nausea, vomiting, difficulty in whistling, loss of appetite and other poor health status leading to reduced social activities, which obviously affect their quality of life. It was found that the quality of life scores of patients with weight loss were significantly lower than those without weight loss. Poor response to treatment Oncology patients with malnutrition often have delayed wound healing, reduced immunity and suppressed T-cell activity, resulting in slower recovery time after surgery. Malnourished patients have lower response to radiotherapy and chemotherapy and more toxic complications. Tumor patients with weight loss have more frequent and severe associated toxic side effects (hand-foot syndrome, mouth sores, etc.) despite receiving smaller doses of initial chemotherapy, and the difference is very significant compared to patients with no weight loss. 4. Increased complications Compared to patients with good nutritional status, malnourished patients have a significantly higher incidence of post-surgical complications such as pulmonary atelectasis, surgical site infection, bacteremia, pulmonary edema, urinary tract infection and sepsis, resulting in longer hospital stays, increased coexisting diseases and a tendency to develop psychiatric disorders. 5. Increased mortality Malnourished tumor patients have higher mortality rate. Patients who are wasted have a poorer prognosis, and wasted tumor patients have more severe dose-related toxicity, along with shorter survival, poor treatment response, reduced quality of life, and decreased physical status. Weight loss was strongly associated with failure-free survival overall survival, and Patients’ weight at the time of initial treatment is an independent prognostic predictor, and patients with tumors that do not continue to lose weight have a longer survival time. 6.Increased medical costs Malnourished tumor patients have longer hospitalization, more frequent hospitalization, higher possibility of re-admission, more visits, and more medical resources, which leads to increased medical costs and increased economic burden for patients, families and the country. Principles of malnutrition treatment Malnutrition is common among malignant tumor patients, therefore, nutritional therapy should become the basic measure and routine means of tumor treatment and be applied to the whole treatment of tumor patients. 1. Countermeasures Tumor itself is the culprit of malnutrition in tumor patients, therefore, effective anti-tumor therapy is the primary measure to treat malnutrition; the nature of tumor is a chronic, low-grade, continuous, irreversible inflammatory response, characterized by metabolic maladaptation as an abnormal metabolic syndrome, inflammatory mediators TNF, IL-6, IL-1 and free radicals play an important role, so the treatment of tumor Therefore, the treatment of malnutrition in tumor patients should be multi-pronged, specifically including: anti-tumor, metabolic regulation, inhibition of inflammation, antioxidant and nutritional support 5 countermeasures. 2. Indications Patients with no malnutrition or no nutritional risk do not need conventional nutritional therapy. Patients with nutritional risk and receiving radiotherapy, chemotherapy and surgery that may aggravate nutritional risk should be given nutritional therapy; patients with severe malnutrition, gastrointestinal dysfunction and side effects caused during antitumor therapy and expected dietary deficiency for more than one week should be given nutritional therapy; patients with nutritional risk without further antitumor therapy need to develop nutritional therapy plan or provide dietary Patients who are at nutritional risk without further antitumor therapy should be given a nutritional treatment plan or diet guidance. Patients with weight loss greater than 20% or oral intake less than 60% who are evaluated by PG-SGA as severely malnourished (score ≥9) or non-terminal are absolute indications for nutritional therapy; patients with weight loss 10%-19%, moderate malnutrition (score 4-8) by PG-SGA and grade 3-4 toxic side effects by radiotherapy are relative indications for nutritional therapy. The relative indications for nutritional therapy. 3.Clinical pathway Nutritional status assessment should be routinely performed after admission of oncology patients to understand the nutritional status of patients. The complete admission diagnosis of a tumor patient should include both tumor diagnosis and nutrition diagnosis. The clinical pathways of nutritional therapy for tumor patients recommended by the Professional Committee of Tumor Nutrition and Supportive Treatment of China Anti-Cancer Association are as follows: Summary Tumor-associated malnutrition is the result of multiple factors, and huge energy consumption and inefficient energy utilization are important causes of malnutrition in tumor patients. The role of inflammatory mediators such as IL-1, IL-6, and TNF is the core pathophysiological mechanism. Malnourished tumor patients have reduced tolerance to radiotherapy, chemotherapy and surgery and reduced sensitivity to respond to antitumor therapy. Malnourished tumor patients have more coexisting diseases and complications, resulting in higher medical costs and shorter survival times. Therefore, nutritional therapy is needed for oncology patients, and nutritional therapy is significant for oncology patients. Nutritional support should be the basic therapeutic measure for tumor patients. A multi-pronged approach is needed to prevent and treat tumor malnutrition, with exact anti-cancer therapy as the prerequisite, standardized nutritional support as the root, reasonable metabolic regulation as the core, effective inflammation inhibition as the key, and moderate oxidative modification as the foundation.