Cancer cachexia is a syndrome involving multiple organ systems throughout the body that commonly exists in patients with malignant tumors, which affects the implementation of treatment plans, reduces the sensitivity of chemotherapy, increases the difficulty of treatment and the occurrence of related treatment complications, seriously affects the quality of life of cancer patients, shortens the survival period, and is the main cause of death of cancer patients. To date, despite the progressive understanding of the mechanisms of carcinomatous cachexia, clinical treatments for carcinomatous cachexia are still very limited. The definition of diagnostic and staging criteria for cancerous cachexia will help standardize the diagnosis of cachexia, improve the understanding of the degree of cachexia in different stages of malignant tumors, and better guide clinical treatment. The rational treatment of malignant disease will further improve the quality of life of tumor patients and prolong their survival time. Diagnosis The understanding of cachexia has gradually increased in the past decade, but there is still a lack of accurate definition and diagnostic and grading criteria for it in both clinical trials and clinical practice. Cancer cachexia is a multifactorial syndrome rather than a simple weight loss. Clarifying the diagnostic and staging criteria of carcinomatous cachexia will facilitate the early treatment of carcinomatous cachexia and thus improve the prognosis of patients with malignancy and cachexia. An international consensus on the criteria for diagnosis and staging of cancer cachexia was recently published in Lancet Oncol, which was jointly presented by experts from eight countries. Cancer cachexia is defined as a multifactorial syndrome characterized by clinical features that are not completely reversible by conventional nutritional support therapy, partial or no sensitivity to nutritional support, with progressive development of reduced skeletal muscle mass (with or without reduced fat mass) and consequent functional impairment, and a pathophysiology characterized by negative nitrogen balance and negative energy balance due to reduced food intake and abnormal hypermetabolism The pathophysiology is characterized by negative nitrogen balance and negative energy balance due to reduced food intake and abnormally high metabolism. The Congress proposed that a 5% weight loss or a body mass index (BMI) < 20 kg/m2 or a 2% weight loss in those who have already experienced a reduction in skeletal muscle mass should be defined as the diagnostic criteria for cancerous cachexia. It also proposed that the classification criteria and clinical treatment of cancerous cachexia should include anorexia or reduced food intake, enhanced catabolism, reduced muscle mass leading to functional impairment and psychosocial impairment. This time, experts from 8 countries jointly launched an international consensus, which divided cachexia into 3 stages: pre-cachexia, cachexia and refractory cachexia. The specific staging criteria are as follows: weight loss <5%, accompanied by anorexia and metabolic changes is to enter the pre-malignant stage; weight loss >5% or BMI <20 kg/m2 within 6 months, weight loss >2%, or limb skeletal muscle index and oligomyositis consistent with (male <7. 26 kg/m2, female <5.45 kg/m2), weight loss >2%, is to begin to enter the Advanced cancer patients with active catabolism, unresponsive to anticancer therapy, low WHO physical status score (3 or 4) and survival of less than 3 months are considered to have entered the refractory cachexia stage. Referring to this international consensus, the development of experimental research and clinical diagnosis and treatment of cachexia due to cancer will be advanced. The definition of cancer cachexia introduced this time takes weight loss as its prominent clinical feature, about half of cancer patients have different degrees of weight loss, and about 86% of cancer patients have weight loss in the last 2 weeks of life. Weight loss >2.75% per month has been used as an important indicator to judge the prognosis of cancer patients, and it is proposed that weight loss in the hormonal state is completely different from that caused by chronic starvation and common anorexia. Cachexia can occur in cancer, AIDS, surgery, severe trauma, malnutrition and sepsis. Cancer cachexia is different from the weight loss of starvation. The brain and red blood cells are depleted of liver glycogen and muscle glycogen at the early stage of starvation, accelerating sugar isogenesis and quickly turning to the use of fat, and free fatty acids are transformed into ketone bodies to be used by peripheral tissues and even for brain tissues, so that muscle is preserved. In anorexia nervosa, 3/4 of the weight loss is due to fat loss and only a small percentage is due to muscle loss. However, weight loss in carcinomatous cachexia is dominated by a loss of skeletal muscle mass with or without a loss of fat mass. Therefore, when weight loss is the same, cancerous cachexia loses more muscle than anorexia nervosa. Although cancerous cachexia is often associated with loss of appetite (15%-40%), it is not the main cause of cancerous cachexia. The degree of reduced intake in malnourished cancer patients does not correspond to the degree of malnutrition, even if muscle and fat loss occurs before the decline in eating. Additional caloric provision does not reverse the changes in body composition of cancerous cachexia, nor does it reverse the onset of cancerous cachexia. Parenteral nutrition can temporarily maintain fat reserves, but it cannot maintain fat-free body weight and prolong the average survival time and long-term survival time of cancerous cachexia. Therefore, the mechanism of cancerous cachexia is more complicated than starvation alone.