Development of Free DNA Multi-target Methylated PCR for Auxiliary Diagnosis of Gastric Cancer

Inclusion Criteria: 1. At least 18 years of age, no gender limitation; 2. those who can accept gastroscopy or provide pathological examination results of postoperative gastric biopsy 3. Patients newly diagnosed with stage I-IV gastric adenocarcinoma who had not received surgery, radiotherapy, chemotherapy, targeted therapy or other anti-tumor intervention before blood collection; 4. There were precancerous lesions and carcinoma in situ in the pathological examination of gastroscopy or esophageal biopsy, and no abnormalities in other gastric lesions, gastroscopy or other cancers. And no previous history of tumor disease. Exclusion Criteria: 1. Previous digestive system tumors, including gastric cancer, esophageal cancer, colorectal cancer, liver cancer, etc.; 2. have a history of other cancers and have not been clinically cured (clinically cured: no recurrence and metastasis within 5 years after surgery); 3. Systemic inflammatory response syndrome; 4. A history of severe cardiovascular disease (e.g., previous myocardial infarction, coronary artery bypass grafting, or coronary stenting); A history of congestive heart failure; Patients with myocardial infarction within 6 months, uncontrolled severe hypertension, etc.) who were deemed unsuitable for inclusion by the investigator; 5. Those who have received major surgical treatment such as blood transfusion or transplantation within 3 months 6. Participants in other interventional clinical researchers, pregnant or lactating women, or patients with autoimmune diseases, genetic diseases, mental diseases, etc., within 3 months. 7. have participated in an "interventional" clinical trial within the past 30 days and have taken the experimental drug; 8. patients with other diseases deemed unsuitable for inclusion by the investigator;