For advanced gastric cancer, surgical resection is the only curable therapeutic strategy. According to minimally invasive approach is adopted in various field of oncologic surgery, laparoscopic gastrectomy with lymph node dissection is becoming a standard not only for early gastric cancer but also for advanced gastric cancer.

The greater omentum is an organ is known to play a role in removing bacteria in the abdominal cavity as a primary defense. Complete resection of the greater omentum has been considered essential to ensure the elimination of micrometastasis during surgery for advanced gastric cancer. However, the oncological effect of total omentectomy is still lack of evidence. Especially in minimal invasive gastrectomy, total omentectomy procedure is known to increases the operating time, increase the risk of bleeding, colonic injury, and postoperative complications such as intra-abdominal abscess, ascites, anastomotic leakage, ileus and wound infections. Therefore, in the case of minimal invasive surgery in early gastric cancer, omentectomy is omitted usually or routinely. Partial omentectomy preserves the omentum more than 3cm away from the gastro-epiploic vessels. Advanced energy devices facilitate partial omentectomy during laparoscopic gastrectomy.

According to the Japanese Gastric Cancer Treatment Guidelines, partial omentectomy (omentum preservation) is feasible for T1 or T2 tumors, and total omentectomy is recommended for clinical T3 or deeper tumors. However, the National Comprehensive Cancer Network(NCCN) guideline suggests total omentectomy and the European Society for Medical Oncology(ESMO) guideline does not mentioned about it.

It is still controversial whether total omentectomy should be performed in advanced gastric cancer. Therefore, we aimed to verify the non-inferiority of partial omentectomy, oncologic safety compared with total omentectomy via multicenter randomized clinical trial.

Inclusion Criteria:

• Histologically proven adenocarcinoma of the stomach
• Age between 20 to 85 years old
• ECOG PS 0-1, ASA class I-III
• Endoscopically Borrmann type I, II, III
• Clinical T3 and T4a tumors with or without regional lymph node metastases (cT3N0M0~T4aN3M0)
• Capable of minimal invasive radical subtotal gastrectomy with R0 resection in preoperative examinations
• Patients who signed an written consent form approved by the Institutional Review Board(IRB) after receiving sufficient explanations of the contents of the clinical trial
• Domestic patients who are able to follow up for 3 years after surgery

Exclusion Criteria:

• Confirmed distant metastasis in preoperative examinations
• Confirmed metastasis in abdominal cavity or distant organs during surgery
• Confirmed no infiltration of the serosa layer or unable to confirm the tumor location during surgery (sT1-2)
• Confirmed invasion of surrounding organs (sT4b)
• History of previous gastrectomy or greater omentum related surgery
• Patients who underwent preoperative treatment (chemotherapy, radiotherapy, or endoscopic submucosal dissection) for recently diagnosed gastric cancer
• Synchronous or metachronous malignancies, which underwent surgery, chemotherapy or radiotherapy within 5 years
• Patients judged to be inappropriate for the study by the physician. (ex. Pregnancy)
• Patients refused to participate after random assignment
• Surgery is not performed until 30 days after consenting to participate
• Patients who has participated in another on-going clinical trial, which is related surgical procedures and survival.