Development and Validation of a Nomogram for Predicting Major Pathological Response Following Neoadjuvant Chemoimmunotherapy in Gastric Cancer

Objective We developed an integrative prognostic nomogram incorporating pretreatment systemic inflammatory response index (SIRI) and lactate dehydrogenase (LDH) levels as biomarkers of immune activity, glycolytic metabolism, and tumor hypoxia to predict treatment response in gastric cancer patients after neoadjuvant chemoimmunotherapy (NACI). Methods A total of 325 patients with gastric cancer who underwent neoadjuvant chemoimmunotherapy and radical resection were retrospectively analyzed. Univariate and multivariate analyses were performed using Logistic regression to screen the independent therapeutic response factors, which were subsequently incorporated into a validated therapeutic response prediction nomogram. Results The major pathological response(MPR) was significantly associated with primary tumor location in the lower stomach ( P =0.008), histological differentiation grade ( P <0.001), SIRI ( P =0.009), microsatellite instability-high (MSI-H) ( P =0.026), monocyte-lymphocyte ratio (MLR) ( P =0.034) and LDH ( P <0.001). Multivariate analysis results showed that primary tumor location in the lower stomach (Odds Ratio (OR)=2.90, 95% Confidence Interval (CI)=1.35-6.22, P =0.006), histological differentiation grade (OR=3.43, 95%CI=1.77-6.63, P <0.001), SIRI (OR=2.02, 95%CI=1.02-3.97, P =0.043), and LDH (OR=1.02, 95%CI=1.01-1.03, P <0.001) were independent prognostic indicators of MPR. The multivariable logistic regression model of these four variables was incorporated into a nomogram with robust MPR predictive accuracy. The model exhibits robust predictive performance with an area under curve of 0.807 in the training set and 0.799 in the testing set, indicating consistent generalizability and clinical utility for real-world implementation. Furthermore, Decision curve analysis (DCA) for the probability of MPR demonstrates the significant clinical utility in predicting MPR outcomes. Conclusion Histological differentiation grade, primary tumor location, SIRI and LDH, are significant in identifying therapeutic response for gastric cancer patients after NACI. The derived nomogram provides clinically actionable predictions to guide therapeutic decisions.