RCT Comparing Reduced-port Robotic and Conventional Laparoscopic Subtotal Gastrectomy

9\. Study Design (Study Groups, Randomization, Blinding, and Study Flow) 9.1 Eligibility Criteria for Participating Surgeons and Standardization and Quality Control of Surgical Procedures Prior to the initiation of this clinical trial, the REPROG-02QC study was conducted to identify and qualify surgeons eligible to participate. Only surgeons approved by the REPROG Committee, based on standardized criteria and assessment of surgical quality, are permitted to participate in this trial. Surgeons' clinical experience and proficiency in surgical techniques are evaluated before being allowed to participate in the randomized controlled trial (RCT). All participating surgeons must apply for participation and obtain approval from their respective Institutional Review Boards (IRBs). They must also fulfill the following requirement: Submission and completion of review for three to four unedited cases of reduced-port robotic gastrectomy, which will be evaluated by the committee for adequacy of lymph node dissection, surgical completeness, and intraoperative performance. In addition, only surgeons affiliated with institutions performing at least 50 gastrectomies per year are eligible to apply for participation in this RCT. The REPROG Committee will review the submitted videos, assign evaluation scores, and determine whether each surgeon is qualified. Only surgeons who are officially qualified through this review process will be permitted to participate in the randomization phase of the RCT. The submitted surgical videos are evaluated by a review committee composed of national and international experts in gastric cancer surgery. The evaluation criteria include adequacy of lymph node dissection, surgical completeness, tissue handling, visualization, and management of intraoperative bleeding. Only those surgeons who meet all the specified surgical evaluation criteria will be permitted to participate in the randomization phase of the trial. Surgeons may be required to undergo re-evaluation or submit additional cases if necessary. This process is designed to ensure quality control of surgical techniques throughout the REPROG study and to secure the internal validity of this multicenter trial. 10.2 Conduct of the Clinical Trial at Participating Institutions and Patient Enrollment The overall coordination and management of this clinical trial will be overseen by the Department of Gastrointestinal Surgery, Severance Hospital, Yonsei University College of Medicine (Coordinating Institution). Surgeons who decide to participate in the trial will receive the necessary documents for IRB submission from the designated study coordinator. Following IRB approval, patient enrollment may begin for those who meet the inclusion criteria. Patient registration and data management will be conducted using a web-based electronic case report form (e-CRF) system provided by Yonsei University Health System. Patient Enrollment Procedure Eligible patients who meet all inclusion criteria and none of the exclusion criteria will be identified. After receiving a detailed explanation of the study, patients will be asked to sign the informed consent form. Subsequently, eligibility will be reconfirmed through a screening checklist on the web-based randomization system provided by Yonsei University. Upon confirmation, patients will be registered and randomized. The point of randomization coincides with the decision to proceed with surgery and the patient's agreement to participate in the clinical study. Enrollment will be competitive among participating institutions. Patients will be withdrawn from the study in the following circumstances: Withdrawal of consent after registration Failure to proceed with surgery within 30 days of registration If more than 30 days have passed, patients must undergo a re-evaluation of eligibility and provide new informed consent to participate in the trial. In the event of erroneous or duplicate registrations identified by individual investigators, the study coordinator must be contacted to correct the records. If identified by the study coordinator, the responsible investigator will be notified to rectify and re-register the patient. (This applies only to subjects in the screening phase before randomization.) The trial will close to enrollment once a total of 538 patients have been randomized and registered. Randomization Method Randomization will be conducted separately for each participating investigator to ensure a 1:1 allocation ratio. A Baseline Number (BN) will be assigned in the order that patients provide informed consent. Eligible patients will then receive a sequential Allocation Number (AN) according to a pre-generated randomization table. Randomized block design will be used, with each investigator considered a stratification factor. Block sizes will not be disclosed to the investigators to preserve the randomness of allocation. Access to the web-based e-CRF will be secured via issued user IDs and passwords for each participating surgeon. Only authorized users with verified login credentials will be permitted to enter data into the system. Study Groups Group A (Conventional Laparoscopy Group): Subtotal gastrectomy with D1+ lymph node dissection performed via the laparoscopic approach. Group B (Reduced-Port Robotic Group): Subtotal gastrectomy with D1+ lymph node dissection performed via the robotic approach using a reduced-port technique (involving three or fewer trocars). DaVicnci SP robotic system will be used as long as the procedure is performed with three or fewer trocars in a reduced-port configuration that meets the study definition of the experimental group.