Safety and Efficacy Evaluation of Single-Port Versus Multi-Port Robotic-Assisted Radical Distal Gastrectomy for Gastric Cancer

Inclusion Criteria:

* Age 18-85 years, irrespective of sex.
* Histologically confirmed primary gastric adenocarcinoma based on endoscopic biopsy.
* The primary tumor is located in the middle or distal third of the stomach, or at another site considered amenable to radical distal gastrectomy. Preoperative evaluation indicates that robot-assisted radical distal gastrectomy is technically feasible and that an R0 resection is anticipated. Patients who have received standard neoadjuvant therapy may also be eligible if reassessment confirms fulfillment of the above surgical criteria.
* Clinical stage cT1-3N0-1M0 according to the 8th edition of the AJCC TNM staging system for gastric cancer, as assessed by gastroscopy and contrast-enhanced computed tomography of the chest, abdomen, and pelvis, with endoscopic ultrasonography, abdominal magnetic resonance imaging, or diagnostic laparoscopy performed when clinically indicated. Preoperative assessment should indicate that R0 resection can be achieved by distal gastrectomy, with no evidence of adjacent organ invasion or distant metastasis.
* No history of other malignancies within the preceding 5 years, except for adequately treated basal cell carcinoma of the skin, squamous cell carcinoma of the skin, cervical carcinoma in situ, or other malignancies with a similarly negligible risk of recurrence.
* American Society of Anesthesiologists (ASA) physical status class I-III.
* Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-1.
* Adequate major organ function, with preoperative assessment confirming fitness for general anesthesia and robot-assisted radical distal gastrectomy.
* Subjects voluntarily participate in the study, fully understand the trial protocol and provide written informed consent.

Exclusion Criteria:

* Body mass index (BMI) \>35 kg/m².
* Previous gastrectomy, or a history of major upper abdominal surgery considered likely to substantially compromise the feasibility or safety of robot-assisted distal gastrectomy, such as complex hepatobiliary-pancreatic surgery or surgery involving the esophagogastric junction. Previous uncomplicated laparoscopic cholecystectomy, appendectomy, or similar procedures are not, in principle, considered exclusionary.
* Tumor-related acute obstruction, active major hemorrhage, or perforation requiring emergency surgery.
* Preoperative confirmation of synchronous multiple gastric cancers or remnant gastric cancer, or the presence or history within the preceding 5 years of another active malignancy that may interfere with study treatment or assessment of study endpoints.
* Preoperative assessment indicating that radical distal gastrectomy is oncologically or technically inappropriate, including anticipated requirement for total gastrectomy, proximal gastrectomy, combined esophagectomy, or any other procedure other than distal gastrectomy.
* Preoperative evaluation or diagnostic laparoscopy demonstrating definite invasion of adjacent organs requiring en bloc multivisceral resection; distant metastasis, including peritoneal, hepatic, pulmonary, osseous, or distant lymph-node metastasis; or positive peritoneal lavage cytology.
* Standard preoperative evaluation indicating that the patient is not currently an appropriate candidate for upfront radical distal gastrectomy and requires initiation or continuation of neoadjuvant therapy or other antineoplastic treatment.
* Concomitant disease requiring an additional surgical procedure at the time of radical gastrectomy that may substantially affect operative duration, perioperative safety, postoperative recovery, or assessment of the primary endpoint.
* Pregnancy or lactation, or planned pregnancy during the study period.
* Severe cardiac, pulmonary, hepatic, or renal dysfunction; severe coagulation abnormalities; uncontrolled infection; or any other medical condition considered to preclude safe administration of general anesthesia or surgical treatment.
* Inability to provide valid informed consent because of cognitive impairment, psychiatric or mental status abnormalities, or other reasons, or inability to comply with protocol-specified treatment and follow-up procedures.
* Any other condition that, in the investigator's judgment, renders the patient unsuitable for participation in the study.