Gastric cancer is one of the most common malignancies, the morbidity and mortality of which are among the highest. In cancer patients, the incidence of cachexia is very high, and even 80% of patients will eventually develop into cachexia. However, once gastric cancer patients develop cachexia, patients are unlikely to obtain clinically significant benefits from conventional treatment. Therefore, it is important to find biomarkers for early detection of cachexia. The investigators carried out a plasma-derived exosomal microRNA(miRNA) study for early diagnosis of cachexia in gastric cancer, and the development of early diagnosis kits for gastric cancer cachexia.