A single-center retrospective study of conversion surgery in stage IV gastric cancer: association with immune checkpoint inhibitor-based chemotherapy.

[BACKGROUND] Stage IV gastric cancer remains challenging to treat despite recent advances in systemic therapy. Among patients with favorable responses to chemotherapy, conversion surgery aiming for R0 resection has shown promise in improving survival. Immune checkpoint inhibitors (ICIs) have become a key component of systemic treatment, but their prognostic impact in the setting of conversion surgery remains unclear.

[METHODS] This retrospective single-center study included 98 patients with gastric cancer who received platinum-based doublet chemotherapy followed by minimally invasive surgery. Patients were stratified into ICI (n = 41) and non-ICI groups (n = 57). Perioperative outcomes, progression-free survival (PFS), and overall survival (OS) were evaluated using Kaplan-Meier analysis and Cox regression models.

[RESULTS] The median operative time was 345 min, and the median blood loss was 5 mL. R0 resection was achieved in 79.6% of cases, and the median hospital stay was 7 days. Clavien-Dindo grade ≥ II complications occurred in 12.2% of patients. ICI-treated patients had significantly longer PFS (hazard ratio [HR], 0.418; P =.0008) and OS (HR, 0.437; P =.024). R0 resection was independently associated with improved PFS (HR, 0.179; P <.0001) and OS (HR, 0.231; P <.0001). Multivariate analysis identified pathological N status, R0 resection, and ICI use as independent predictors of PFS.

[CONCLUSION] Among patients who underwent conversion surgery in this real-world cohort, those treated with ICI-based chemotherapy demonstrated more favorable long-term outcomes than those treated with chemotherapy alone. Although our findings do not demonstrate a causal relationship of ICI therapy on resectability, they suggest that ICI-based chemotherapy may be associated with improved survival in appropriately selected patients with human epidermal growth factor receptor 2-negative stage IV gastric cancer. Prospective studies are warranted to clarify optimal indications and perioperative strategies for integrating ICI-based regimens into conversion treatment.