Gastric cancer is a common malignant tumour worldwide, and in China, the incidence and mortality rates of gastric cancer remain high. Standardised surgical treatment is effective, but the normal structure of the stomach undergoes irreversible changes, leading to a series of adverse reactions. At the same time, some early-stage gastric cancer patients cannot have the lesions completely removed endoscopically, and conventional surgery can affect postoperative normal life. Therefore, laparoscopic and endoscopic cooperative surgery has become a focus for precise stomach-preserving surgery. Participants meeting the surgical criteria are selected, and after discussing the treatment plan with their families and signing informed consent forms, relevant examinations are completed. During surgery, lesions are explored together using laparoscopy and endoscopy, then a fluorescent tracer is injected around the lesion and the lesion boundary is marked. Fifteen minutes after injecting the fluorescent tracer, the illuminated perigastric lymph nodes are the sentinel lymph node region (SLNB), and all fluorescent lymph nodes (sentinel lymph nodes) are removed and sent for intraoperative frozen pathology. If the SLNB is negative: a dual-endoscope combined local gastric resection (endoscope combined with laparoscopic local gastric resection or a modified procedure) is performed to completely remove the lesion, ensuring a negative margin. If the SLNB is positive: immediate conversion to laparoscopic-assisted radical gastrectomy (D2 lymph node dissection) is carried out. For SLNB-negative cases, the dual-endoscope combined local gastric resection specimen is placed in a retrieval bag for full removal and examination, with the stomach wall incision then closed by suturing or using a stapler. Postoperative follow-up includes monitoring tumour outcomes and quality of life.

Stomach cancer is one of the common malignant tumours worldwide, and in China, the incidence and mortality rates of stomach cancer remain high, posing a major public health burden. With the widespread implementation of stomach cancer screening in China, the detection rate of early-stage stomach cancer has significantly increased, now accounting for 19.5% of all stomach cancer cases. Early-stage stomach cancer (T1 stage) has a much better prognosis than advanced-stage cancer, with a 5-year survival rate exceeding 90% after standard treatment. Endoscopic submucosal dissection (ESD), due to its minimally invasive nature and ability to preserve stomach function, has become the standard treatment for certain cT1a-stage stomach cancers. However, for early-stage stomach cancer patients with a higher risk of lymph node metastasis, the lymph node metastasis rate can be close to 20%. In this context, if these patients only undergo endoscopic removal, they may face a higher risk of tumour residue. The traditional standard treatment is radical gastrectomy, usually combined with regional lymph node dissection (D1 or D2). Although this surgery is effective for cancer control, it can cause significant trauma, leading to irreversible changes to the patient's post-operative physiology and function, as well as long-term complications such as malnutrition, reflux oesophagitis and reduced quality of life, which have become key issues affecting the recovery of early-stage stomach cancer patients.

With the development of endoscopic technology (gastroscopy) and laparoscopic minimally invasive surgery, the concept of "function-preserving" surgery for early gastric cancer has been gaining increasing attention. This concept aims to minimise surgical trauma and preserve the anatomical structure and physiological function of the stomach while ensuring oncological safety. Achieving this goal relies heavily on the development and integration of two key techniques. First is Laparoscopic Sentinel Node Navigation Surgery (LSNNS). Sentinel lymph nodes are the first or group of lymph nodes along the primary tumour's lymphatic drainage pathway, and their pathological state is considered to highly predict metastasis in all lymph nodes in that region. In gastric cancer surgery, by injecting tracers (such as the fluorescent dye indocyanine green) under the mucosa around the tumour, and using the magnified view and fluorescence imaging system of laparoscopy, these sentinel lymph nodes can be located and removed in real time for intraoperative rapid pathological examination. The National Cancer Center in South Korea conducted a multicentre phase III randomised controlled clinical trial (SENORITA) on laparoscopic sentinel node navigation surgery for function-preserving surgery in early gastric cancer. In the LSNNS group, 210 patients (81%) underwent stomach-preserving surgery, and the results showed no significant difference in postoperative complication rates, 5-year local recurrence, disease-free survival (DFS), and overall survival (OS) compared to conventional laparoscopic radical gastrectomy. However, the LSNNS group had significantly better postoperative quality of life. These study results suggest that due to the complexity of gastric cancer lymphatic drainage and the skip and uncertain nature of metastasis, detecting the sentinel lymphatic basin (SLB) can provide a more comprehensive understanding of sentinel nodes, offering precise guidance for individualised lymph node dissection and avoiding unnecessary extended lymph node removal, reducing surgical trauma and related complications without compromising oncological outcomes.

Laparoscopic and endoscopic cooperative surgery (LECS) combines the advantages of laparoscopic internal view and operation with the precise localisation and removal capabilities of endoscopy. It's become a hot research topic in stomach-function-preserving surgery in recent years. Endoscopy provides a high-definition view of the mucosal surface from inside the cavity, allowing precise marking of tumour boundaries and submucosal dissection, while laparoscopy offers an external view of the serosal surface, enabling reliable full-thickness gastric wall resection, accurate suturing and regional lymph node inspection and management. Main LECS procedures include laparoscopic-assisted endoscopic full-thickness resection (LAEFR), endoscope-assisted wedge resection (EAWR), classic LECS and modified LECS. Several studies both domestic and international have shown LECS has advantages in treating various gastrointestinal tumours, but standardised procedures for early gastric cancer are not yet established, and current data is largely from retrospective studies, lacking high-quality prospective evidence.

Inclusion Criteria:

1. Age 18-80, any gender;
2. Gastric adenocarcinoma confirmed by gastroscopic biopsy, with a single lesion;
3. Clinical staging cT1N0M0 based on enhanced CT, endoscopic ultrasound and other imaging evaluations (tumour limited to the mucosa or submucosa with no evidence of lymph node or distant metastasis);
4. Absolute indications for endoscopic submucosal dissection (ESD), with lesions no larger than 5cm, or cases where endoscopic removal is difficult. Absolute indications for ESD (differentiated carcinoma, mucosal T1a stage, without ulcer ≤2 cm or with ulcer ≤3 cm; undifferentiated carcinoma without ulcer ≤2 cm. Difficult cases for endoscopic removal: negative "lifting sign", laterally spreading tumours and scar ulcers etc.);
5. Meets eCURA score criteria for non-curative ESD requiring additional surgery;
6. ECOG performance status 0-1;
7. Patient fully informed and consents, signing the consent form. Note: For inclusion, meeting either criterion ④ or ⑤ is sufficient.

Exclusion Criteria:

1. Pregnant or breastfeeding women;
2. Those with a history of major upper abdominal surgery where severe abdominal adhesions are expected;
3. Patients with recurrent gastric cancer, multiple primary tumours, or those who have undergone preoperative chemoradiotherapy;
4. Those meeting ESD indications and having completed curative endoscopic resection according to eCURA standards [12,13];
5. Patients with other unresectable malignant tumours;
6. Those with severe heart, lung, liver, or kidney dysfunction who cannot tolerate general anaesthesia and surgery;
7. Those allergic to indocyanine green (ICG) or nano carbon tracers;
8. Those with mental illness who cannot cooperate with the study and follow-up.