Diagnostic Accuracy of Staging Laparoscopy and Development of a Simple Predictive Score for Peritoneal Disease in Advanced Gastric Cancer

Introduction Staging laparoscopy (SL) enables direct detection of peritoneal disease (PD), including peritoneal dissemination (P1) and positive peritoneal cytology (CY1), which are often undetectable by preoperative imaging in gastric cancer (GC). This study aimed to evaluate the diagnostic accuracy of SL and to develop a simple preoperative scoring system for predicting peritoneal disease. Methods A total of 889 patients with advanced GC who underwent SL were retrospectively reviewed. After excluding 128 post-chemotherapy cases, 761 treatment-naive patients were analyzed. Clinicopathologic variables were compared between PD– and PD+ groups, and predictors of peritoneal disease were identified. A simple predictive score was constructed based on significant independent factors. Results Peritoneal disease was detected at SL in 418 patients (54.9%). Positivity rates by indication were 61.7% for type 4, 51.1% for large type 3 (≥8 cm), 24.2% for bulky or para-aortic lymph node enlargement, and 76.8% for CT-suspected dissemination. The sensitivity, specificity, and accuracy of SL were 94.6%, 100%, and 96.8%, respectively. Multivariate analysis identified four independent predictors of peritoneal disease: CA19-9 >37 U/mL, CA125 >35 U/mL, poorly differentiated or signet-ring cell histology, and pan-regional tumor involvement. A scoring system (range 0–6) based on these variables demonstrated a stepwise increase in peritoneal disease incidence, from 32.4% for score 0 to 100% for score 6. Conclusions SL offers excellent diagnostic performance for peritoneal disease in advanced GC. The proposed four-factor predictive score provides a simple and practical tool for estimating peritoneal disease risk, potentially allowing for more selective and rational use of SL.