The Role of Diagnostic Laparoscopy in Staging and Treatment Planning of Gastric Cancer: A 400-Patient Retrospective Cohort Study

Background: Accurate staging in gastric cancer is essential for optimal treatment planning. Diagnostic laparoscopy (DL) plays a crucial role in detecting occult peritoneal metastases not identified by conventional imaging. This study aimed to evaluate the impact of DL on clinical decision-making and treatment allocation in patients with gastric cancer. Methods: We retrospectively analyzed consecutive patients treated between June 2016 and March 2026 at a tertiary Surgical Oncology Center. All patients underwent diagnostic laparoscopy with peritoneal lavage and biopsies. Patients were stratified according to the Peritoneal Cancer Index (PCI) and directed to appropriate treatment pathways, including CRS + HIPEC, PIPAC combined with systemic chemotherapy, or neoadjuvant chemotherapy followed by surgical re-evaluation. Results: Occult peritoneal metastases were detected in 20% of patients (80/400). Among patients with peritoneal metastasis, 70 patients ultimately underwent CRS + HIPEC and 39 underwent PIPAC-based treatment. Among these 70 patients, 53 patients with PCI < 7 were initially allocated to CRS + HIPEC and an additional 17 patients with newly detected limited peritoneal disease (PCI < 7) underwent CRS + HIPEC following restaging laparoscopy after neoadjuvant chemotherapy, resulting in a total of 70 patients in the CRS + HIPEC group. In the CRS + HIPEC group, the 1-year survival rate was 70% with a morbidity rate of 25.7%. In the PIPAC group, the 1-year survival rate was 50% with a morbidity rate of 25.6%. Among patients receiving neoadjuvant chemotherapy, disease progression was detected in 14% during restaging laparoscopy. Palliative surgery provided effective symptom control in inoperable patients, with a 1-year survival rate of approximately 15%. Conclusions: Diagnostic laparoscopy provides additional staging information and guides treatment allocation in patients with advanced gastric cancer. PCI-based assessment enables individualized selection of CRS + HIPEC, PIPAC, or systemic treatment strategies. However, the present study was not designed to determine whether DL-guided treatment allocation improves survival, and the observed survival outcomes should therefore be interpreted as descriptive real-world outcomes rather than evidence of treatment benefit.