Endoscopic Cryoablation Combined With PD-1 in Advanced Gastric Cancer

Inclusion Criteria: 1. Patients diagnosed with advanced gastric cancer (stage IV in AJCC 8th edition staging, including locally progressive gastric cancer with unresectable factors (IVa) and gastric cancer with distant metastases (IVb); Bowman's staging type I, II, and III), who are unable to be surgically resected or do not tolerate surgical resection, and who have undergone progression after 1-2 lines of conventional chemotherapy; 2. Age greater than 18 years and less than 80 years; 3. WHO pathology type: adenocarcinoma, neuroendocrine tumor; 4. Expected survival greater than 3 months and controllable distant metastases as judged by the physician; 5. Important organ functions must be met: ① Liver function: ALT and AST ≤ 2.5 times the positive range, total bilirubin ≤ 2.0mg/dL; ② Renal function: creatinine clearance ≥ 40mL/min calculated using the EPI formula; 6. Blood routine: Hgb≥70g/L,ANC≥1.5×109/L,PLT≥80×109/L; 7. Coagulation function: PT and APPT \<2 times the normal value; 8. Pregnancy test must be negative in women of childbearing age; 9. ECOG score ≤2; 10. Signed informed consent. Exclusion Criteria: 1. Pregnant or breastfeeding women, or women with pregnancy plans within six months; 2. Infectious diseases (e.g. AIDS, syphilis, active tuberculosis); 3. Patients with active hepatitis B or C infection; 4. Combination of other primary malignant tumors; 5. Patients who have participated in a clinical trial within one month; 6. Patients taking antiplatelet or anticoagulant drugs within the last week; 7. Patients with gastric cancer combined with active bleeding; 8. Large amount of ascites (ascites ≥3000ml); 9. Cardia obstruction or pyloric obstruction; 10. patients with combined active infection or autoimmune disease; 11. Those who the doctor thinks there are other reasons not to be included in the treatment.