Background: The main treatment methods for early gastric cancer (EGC) include endoscopic submucosal dissection (ESD) and radical gastrectomy. However, appropriate treatment for patients who exceed the absolute indications for ESD remains unestablished. In China, evidence-based medicine for the expanding indications of ESD and accurate diagnostic staging for EGC patients are lacking. Thus, clinical studies involving Chinese patients with EGC are necessary to select appropriate treatment options and promote China's expanded indications for ESD and diagnostic staging scheme.

Methods: This is a multicenter, ambispective, observational, open-cohort study that is expected to enroll 554 patients with EGC. The study was launched in May 2018 and is scheduled to end in March 2022. All enrolled patients should meet the inclusion criteria. Case report forms and electronic data capture systems are used to obtain clinical data, which includes demographic information, results of perioperative blood- and auxiliary examinations, surgical information, results of postoperative pathology, and the outcomes of postoperative recovery and follow-up. Patients are followed up every 6 months after surgery for a minimum of 5 years. The primary endpoint is the rate of lymph node metastasis (LNM), whereas the secondary endpoints include the following: consistency, sensitivity, and specificity of the results of preoperative examinations and postoperative pathology cut off values for LNM; logistic regression model of expanded indications for ESD; and incidence of postoperative complications within the 30-day and 5-year relapse-free survival rates.

This study will explore and evaluate expanded indications for ESD that match the characteristics of the Chinese population in patients with EGC and will introduce a related staging procedure and examination scheme that is appropriate for China. Ethical approval was obtained from all participating centers. The findings are expected to be disseminated through publications or presentations and will facilitate clinical decision-making in EGC.

Inclusion Criteria:

Patients aged 18-75 years (regardless of sex). Patients with tumor diameter > 30 mm, ulceration (UL)(+), and differentiated mucosal carcinoma (T1a).

Patients with tumor diameter > 30 mm and differentiated, submucosal invasion depth < 500 μm (T1b SM1).

Patients with tumor diameter ≤ 30 mm and differentiated submucosal carcinoma (T1b).

Patients with tumor diameter ≤ 20 mm, UL(-), and undifferentiated (T1a). Patients with tumor diameter > 20 mm, UL(-), and undifferentiated (T1a). Patients with tumor diameter ≤ 30 mm, UL(+), and undifferentiated (T1a). Patients with tumor diameter > 30 mm, UL(+), and undifferentiated (T1a).

Exclusion Criteria:

Patients with gastric stump cancer. Patients with recurrent gastric cancer. Patients with multiple primary malignant tumors.

This study aims to explore and evaluate expanded indications for ESD that match the characteristics of the Chinese population in patients with EGC, and to introduce a staging procedure and examination scheme for EGC that is appropriate for China.