Clinical impact of gastrectomy in surgically proven stage IV gastric cancers: retrospective analysis from Korean multicenter dataset (PASS-META).

Background: Palliative resection for metastatic gastric cancer is not recommended in current practice guidelines; however, it is frequently performed based on clinical considerations. Prospective trials face challenges, necessitating large-scale retrospective analyses to provide clinical evidence.

Methods: The PASS-META study group established a cohort of 983 patients with gastric cancer with surgically confirmed metastatic lesions treated at five major Korean institutions from 2014 to 2021, collecting 126 variables from preoperative, operative, and postoperative data through hospital records. The correlation between gastrectomy and survival outcomes was investigated using inverse probability of treatment weighting (IPTW) and standardization to estimate counterfactual outcomes.

Results: Machine learning-based imputation and statistical causal survival analysis revealed that gastrectomy was found to significantly improve survival in patients with limited peritoneal metastasis (P1 or P2; RR: 0.90, 95% CI 0.85-0.94), as well as in those with distant lymph node metastasis (dLN1; RR: 0.92, 95% CI 0.91-0.94) and hepatic metastasis (H1; RR: 0.92, 95% CI 0.82-1.00), suggesting a potential survival advantage across these subgroups. No survival benefit was observed in patients with severe peritoneal metastasis (P3). Among patients with P1-P2 metastasis, extensive lymph node dissection improved the 5-year survival rates compared with limited dissection, whereas minimally invasive surgery did not affect the survival outcome. Although gastrectomy increased the postoperative hospital stay and delayed the initiation of the first postoperative chemotherapy compared to patients without gastrectomy, it did not affect the total number of chemotherapy cycles.

Conclusion: This study suggests that gastrectomy offers a significant survival benefit to patients with surgically proven stage IV gastric cancer and limited peritoneal metastasis (P1/P2), distant lymph node (dLN1), or hepatic metastases (H1). Furthermore, specific surgical procedures such as extended lymph node dissection or minimally invasive surgery may be considered for patients undergoing gastrectomy.