Inclusion Criteria
1. Patients aged 18-80 years, regardless of gender;
2. Siewert III of the esophagogastric junction adenocarcinoma: Stage Ⅰ(cT1-2N0M0) or adenocarcinoma of the upper part of the stomach： Stage Ⅰ(cT1-2N0M0), Stage II( cT1-2N1-3M0 / cT3-4N0M0), Stage III(cT3-4aN1-3M0); patients who are suitable for surgery according to the 8th AJCC clinical staging of gastric cancer;
3. Primary lesion diagnosed by preoperative endoscopic end pathology: tumor diameter \<4 cm and located in the upper part of the stomach (including the esophagogastric junction), histologically confirmed adenocarcinoma;
4. Preoperative ASA score: I, II, or III;
5. Preoperative Karnofsky physical status score: ≥ 70%; or preoperative ECOG physical status score: ≤ 2;
6. No distant metastases (confirmed by preoperative chest X-ray, abdominal ultrasound, and upper abdominal CT); no peritoneal implant metastases (confirmed by laparoscopic exploration surgery);
7. R0 surgical outcome is expected to be obtained with radical gastrectomy of D2 proximal gastric cancer;
8. Patients and their families voluntarily participate in this study and sign the informed consent form after understanding the study content.
Exclusion Criteria
1. Patients received any preoperative treatment, such as chemotherapy, radiotherapy, targeted therapy or immunotherapy; preoperative neoadjuvant chemotherapy recipients;
2. Patients with clinical stage exceeding Siewert III of the esophagogastric junction adenocarcinoma: Stage Ⅰ(cT1-2N0M0) or more than adenocarcinoma of the upper part of the stomach: Stage Ⅰ(cT1-2N0M0), Stage II(cT1-2N1-3M0/cT3-4N0M0), Stage III(cT3-4aN1-3M0);
3. Patients with acute infections, especially biliary tract infections;
4. Patients with complications of gastric cancer (bleeding, perforation, obstruction) requiring emergency surgery;
5. Patients with uncorrectable coagulation dysfunction;
6. Patients with vital organ failure, such as heart, lung, liver, brain, kidney, etc.
7. Severe central nervous system disease, mental disorders, or impaired consciousness;
8. Pregnant or lactating women;
9. Patients with distant metastases;
10. Patients with a primary tumor at another site diagnosed within the past 5 years;
11. Preoperative ASA score: ≥ IV;
12. Preoperative ECOG physical status score: ≥ 2;
13. History of continuous systemic corticosteroid therapy within the past 1 month;
14. History of unstable angina, myocardial infarction, cerebral infarction, or cerebral hemorrhage within the past 6 months;
15. Patients with concurrent surgical treatment of other diseases;
16. Patients with immunodeficiency, immunosuppression, or autoimmune diseases (organ transplant requiring immunosuppressive therapy within the past 5 years, allogeneic bone marrow transplant patients, taking immunosuppressive drugs, etc.);
17. Patients with concurrent participation in other clinical studies;
18. Patients refusing to sign an informed consent form to participate in this study;
19. Preoperative imaging: regional fusion of enlarged lymph nodes (maximal diameter \> 3 cm).
