Pretreatment Claudin-18.2 Expression Predicts Poorer Survival Outcomes in Locally Advanced Gastric Cancer Treated...

Background/Objectives: Claudin-18.2 (CLDN18.2) has recently emerged as a therapeutic target in gastric cancer; however, its prognostic relevance in the neoadjuvant setting remains insufficiently defined. We evaluated the clinical significance of CLDN18.2 and fibroblast growth factor receptor 2b (FGFR2b) expression in patients with locally advanced gastric cancer treated with neoadjuvant therapy. Methods: This retrospective single-center study included 64 patients with locally advanced gastric cancer who received neoadjuvant chemotherapy followed by curative surgery. Pretreatment endoscopic biopsy specimens were analyzed using immunohistochemistry to assess CLDN18.2 and FGFR2b expression. Survival outcomes were evaluated using Kaplan-Meier analysis and Cox proportional hazards regression models. Results: CLDN18.2 positivity was detected in 29.7% of patients and was not associated with baseline clinicopathological characteristics or pathological treatment response. However, CLDN18.2-positive tumors demonstrated significantly shorter relapse-free survival (median 19.0 vs. 36.6 months, p = 0.038) and overall survival (median 28.9 vs. 53.4 months, p = 0.005). In multivariable analysis, CLDN18.2 positivity remained an independent predictor of relapse-free survival. FGFR2b positivity was observed in 14.1% of patients and was evaluated descriptively due to limited case numbers. Conclusions: CLDN18.2 expression may represent a clinically relevant prognostic biomarker reflecting aggressive tumor biology in locally advanced gastric cancer treated with neoadjuvant therapy.