The aim of this study is to verify the safety and efficacy of single or reduced ports laparoscopic gastrectomy for advanced gastric cancer.

Since two cases of single-incision laparoscopic gastrectomy in early gastric cancer were reported in 2011, the safety and efficacy of single-incision laparoscopic gastrectomy in early gastric cancer have been reported several times.

Recently, the feasibility of laparoscopic single-incision gastrectomy in some advanced gastric cancer has already been reported.

The total number of retrieved lymph nodes during gastric cancer surgery is one of the most important indicators for securing oncological safety and predicting the therapeutic effect in gastric cancer surgery.

Therefore, in order to prospectively evaluate the efficacy of single-incision or reduced-port laparoscopic gastrectomy for advanced gastric cancer as an oncological operation, the purpose of this study is to evaluate the number of resected lymph nodes after D2 lymph node dissection in single-incision or reduced-port laparoscopic gastrectomy for advanced gastric cancer.

All surgeries are performed as single-incision laparoscopic surgery using a 3-4 cm umbilical incision, and D2 lymph node dissection is performed according to the Japanese gastric cancer treatment guidelines 2018 by the Japanese Gastric Cancer Association.

When an additional trocar is required, it is classified as reduced port laparoscopy when one additional trocar is added.

For surgical assistance, including effective visual field development during surgery, a self intra-corporeal retractor (FJ clip®, or Internal organ retractor®) or an additional trocar (up to 1 trocar) could be used.

An articulating laparoscopic surgical instrument (Artisential ®) can be used for safe access to difficult areas of the D2 lymph node dissection, such as the superior border of the pancreas.

Before the end of the surgery, the surgeon evaluates the completeness of D2 lymph node dissection and radical resection of the primary tumor(R0 resection). If insufficient, the operation is converted to multi-port laparoscopic surgery or open surgery, and additional D2 lymph node dissection and tumor resection are performed, and those cases are recorded separately in the registry as multiport/open conversion.

Inclusion Criteria:

• Patients who have confirmed that participants have advanced gastric cancer at clinical stage T2 or higher and who can undergo distal gastrectomy for primary gastric cancer who have consented to single-port and reduced-port laparoscopic gastric cancer surgery
• Patients diagnosed with locally advanced gastric cancer in which no enlarged lymph nodes were observed in the preoperative examination, or lymph node metastases confined to the left gastric artery or perigastric area were suspected.
• Those who have not been treated for systemic inflammatory disease before surgery

Exclusion Criteria:

• Those who have previously had gastrectomy.
• Those who have a laparotomy except for appendectomy, cholecystectomy or cesarean section.
• Patients with clinical (preoperative or intraoperative) stage T4b accompanied by infiltration of surrounding organs
• Those with bulky lymph nodes (single nodules over 3 cm or multiple nodules over 1.5 cm)
• Patients with confirmed distant metastasis (M1)
• Severe liver cirrhosis
• Patients who is judged by the investigator to be inappropriate for this study
• Patients who are taking antithrombotic drugs, including antiplatelet drugs and anticoagulants, and cannot safely stop before surgery