Patients with locally advanced gastric adenocarcinoma (CT2-4a N-/+ M0) were selected as study subjects to investigate the safety, efficacy, and feasibility of ICG near-infrared imaging tracing in 3D plus ultra high resolution laparoscopic gastrectomy with lymph node dissection for gastric cancer.

1. Research purpose: Patients with locally advanced gastric adenocarcinoma (CT2-4a N-/+ M0) were selected as study subjects to investigate the safety, efficacy, and feasibility of ICG near-infrared imaging tracing in 3D plus ultra high resolution laparoscopic gastrectomy with lymph node dissection for gastric cancer.
2. Research design: Prospective, single-center, randomized controlled, open-control, parallel assignment, superiority test.

2.1 Case group Group A (Study Group 1, 234 cases): ICG near-infrared imaging tracing in 3D plus ultra high resolution laparoscopic gastrectomy with lymph node dissection; Group B (Study Group 2, 234 cases): ICG near-infrared imaging tracing in ultra high resolution laparoscopic gastrectomy with lymph node dissection; Group C (Control Group 2, 234 cases) 3D laparoscopic gastrectomy with lymph node dissection

2.2 Estimate Sample Size The three-year disease-free survival (DFS) was the main effectiveness evaluation index in this study. The study implemented a superiority test (unilateral), assuming that both the study group's three-year DFS would be better than that of control group, according to previous research results of laparoscopic surgery for locally advanced GC in which the three-year DFS was 65.2%; therefore, the 3-year DFS of the control group would be 65.2%, assuming that the 3-year DFS of the experimental group could be increased by 12% to 77.2%. With an inspection level 0.0125 (unilateral) and an inspection efficiency of 0.8 and using PASS 11 log-rank tests (Lakatos) [Proportion surviving] the calculated sample size was N=211; namely, each group needed 211 people, considering cases of possible exclusion and loss to follow-up (10% drop out rate). The final sample size for each group was 234 cases, for a total of 702 cases.

2.3 randomization After laparoscopic exploration and confirmation that the cases complied with the standards, they were included in the randomized groups in this study. SAS 9.2 was used to produce a serial number ranging from 0001 - 702 corresponding to the treatment allocation, which was reserved in the data center and research center.

2.4 Blinding Method: This research adopts an open design.

2.5 Research cycle: Estimated enrollment cycle: complete enrollment within 2 years. Follow-up period: the enrollment of the first case was the starting point for follow-up. And the enrollment of last case to the postoperative pathology report (generally 2 weeks after surgery) was the endpoint of follow-up for secondary outcomes. Three years after the last case was enrolled was the follow-up endpoint for the main outcomes.

Estimated time: 2023.12-2025.12 (complete enrollment) to 2028.12 (complete follow-up)

Study Objects All patients who meet the inclusion criteria and do not conform to the exclusion criteria are qualified for this study.

Inclusion Criteria:

1. Age from 18 to 75 years
2. Primary gastric adenocarcinoma (papillary, tubular, mucinous, signet ring cell, or poorly differentiated) confirmed pathologically by endoscopic biopsy
3. cT2-4a, N-/+, M0 at preoperative evaluation according to the AJCC Cancer Staging Manual, 8th Edition
4. No distant metastasis, no direct invasion of pancreas, spleen or other adjacent organs in the preoperative examinations
5. Performance status of 0 or 1 on the ECOG (Eastern Cooperative Oncology Group) scale
6. ASA (American Society of Anesthesiology) class I to III
7. Written informed consent

Exclusion Criteria:

1. Women during pregnancy or breast-feeding
2. Severe mental disorder
3. History of previous upper abdominal surgery (except for laparoscopic cholecystectomy)
4. History of previous gastric surgery (including ESD/EMR for gastric cancer)
5. Enlarged or bulky regional lymph node (diameter over 3cm) supported by preoperative imaging
6. Other malignant disease within the past 5 years
7. History of previous neoadjuvant chemotherapy or radiotherapy
8. History of unstable angina or myocardial infarction within past six months
9. History of cerebrovascular accident within past six months
10. History of continuous systematic administration of corticosteroids within one month
11. Requirement for simultaneous surgery for other disease
12. Emergency surgery due to complication (bleeding, obstruction or perforation) caused by gastric cancer
13. FEV1 (forced expiratory volume in one second)<50% of predicted values
14. Diffuse invasive gastric cancer
15. History of an iodine allergy
16. Patients who declined laparoscopic surgery