Designed as a single arm multi-center prospective phase II trial, which evaluates the number of dissected lymph nodes in the N2-area as a surrogate parameter for adequate D2 lymphadenectomy in robotic distal gastrectomy (RDG) for clinical stage II or III gastric cancer.

The number of retrieved LNs in the N2 area after RDG is going to be calculated according to the pathology reports and comparative analysis to a historic group undergone open surgery for clinical stage II or III gastric cancer at the NCC Korea last year.

METHODS AGAINST BIAS Minimizing selection bias: After initiation of the study, all patients will be screened consecutively and all eligible patients will be asked to enrol in the trial. The trial is designed as a prospective multi-center phase II trial. Patients are going to be allocated to RAG after giving signed consent after sufficient consideration time.

Minimizing performance bias: The study is planned as a prospective single arm multi-center trial, as the retrospective data suggest that there is no disadvantage in lymph node retrieval after RAG compared to LAG. Surgery is going to be performed according to the guidelines of the Japanese Research Society for the Study of Gastric Cancer (3rd edition). Japanese randomized controlled trials have proven effectiveness of adequate D2 lymphadenectomy in several randomized controlled trials. As number of dissected lymph nodes is a surrogate marker for adequate lymph node dissection, only patients with at least 25 lymph nodes removed (as obtained from pathology report) will be definitively included in the data assessment. Further lymph node stations No. #7, #8a, #9, #11p, #12a for subtotal gastrectomy according to the Japanese Guideline have to be dissected out of the surgical specimen and analyzed separately in the pathologic workup. All patients in the trial are going to be analyzed, as success rate of LN dissection in the N2-area is the primary endpoint. Surgery in the trial must be performed by a board certified surgeon who has taken part in a trial specific training course. Potential learning curve artefacts are negligible because the RAG is going to be performed by surgeons who are highly trained and experienced in robotic gastrectomy.

Participating surgeons should have experience as an operator of over 50 cases of open gastrectomy, over 50 laparoscopic gastrectomy, and over 15 cases of robotic gastrectomy. Furthermore, surgical quality will have to be enforced by intraoperative video documentation. Also, pictures of nodal dissection area after resection should be submitted to have a quality assurance.

Minimizing detection bias: Patients are going to regularly undergo standardized follow-up visits at 6, 12, 18, 24, 30, 36, 48, 60 months to be evaluated disease status with abdominopelvic CT. EGD will be done on 3, 12, 24, 36, 48 and 60 months.

Inclusion Criteria:

• Histologically proven adenocarcinoma of the stomach in patients that have not received any previous treatment for their cancer
• Tumours should be stage II or III according to the UICC 7th edition with no sign of distant metastasis and deemed resectable (R0) by the operating surgeon on preoperative staging by EGD, and CT of abdomen and pelvis
• Location of the tumor at the pylorus, antrum, angle, lower body and midbody to allow subtotal gastrectomy
• Age ≥ 19 years
• Written informed consent

Exclusion Criteria:

• Performance status ≥3

• Patients not eligible for surgery (ASA >=4)

• History of another primary cancer, except curatively treated in situ cervical cancer, curatively resected non-melanoma skin cancer. The inclusion of patients with other types of cancer that were successfully treated and did not recur within the last 5 years prior to study enrolment have to be discussed with the principal investigator.

• Evidence of distant metastasis on clinical staging

• Primary tumour deemed unresectable by operating surgeon

• Inadequate organ function as below

  • Bone marrow function defined as: (ANC ≤1.0x109/l, WBC (total) ≤ 2.5x109/l, Platelet Count ≤ 70x109/l, Haemoglobin ≤ 8 g/dl (can be post-transfusion)

    • Renal function with serum Creatinine ≥1.5 mg/dL) ③ Liver function defined as (Total Bilirubin≥ 2.0x (ULN), ALT/AST ≥2.5x ULN) ④ Coagulation profile: with PT (INR) ≥1.5, aPTT(sec) ≥1.5xULN

• Women of childbearing potential should have a negative pregnancy test within 7 days prior to commencing treatment, and must take adequate contraceptive precautions

• Simultaneous participation in another clinical trial.