Integration of Systemic Inflammation Response Index (SIRI) and Clinicopathological Factors Enhances Survival Prediction in Colorectal Cancer: A Retrospective Cohort Study

Background Colorectal cancer (CRC) is a leading cause of cancer-related mortality worldwide. The current TNM staging systems exhibit limited prognostic accuracy because they do not account for host inflammatory responses. This study aimed to develop and validate a novel prognostic nomogram integrating clinicopathological features with systemic inflammatory biomarkers to improve survival prediction in patients with CRC after radical resection. Methods In this retrospective cohort study, clinical data from‌ 324 patients with CRC who underwent surgery between January 2010 and March 2020 were analyzed. Preoperative hematological indices‌ (including NLR, PLR, LMR, FAR, ‌dNLR‌, MCVL, SIRI, SII, PNI, IIC, PINI, HALP) ‌and clinicopathological variables were assessed., Variable selection ‌was conducted‌ using univariate Cox analysis, LASSO regression (Lambda.1se) and multivariate Cox analysis. The final model was constructed ‌ as a nomogram and validated for 1-, 3-, and 5-year overall survival (OS) predictions using ROC analysis, calibration curves, and decision curve analysis (DCA). Results Multivariate analysis identified four independent prognostic factors: N stage (N1: HR = 2.72, 95% CI 1.51–4.89, p < 0.001; N2: HR = 5.26, 95% CI 2.60–10.67, p < 0.001), vascular invasion (HR = 6.02, 95% CI 3.79–9.58, p < 0.001), perineural invasion (HR = 2.02, 95% CI 1.29–3.16, p = 0.002), and SIRI ≥ 2.39 (HR = 2.03, 95% CI 1.33–3.09, p < 0.001). The nomogram demonstrated ‌significantly‌ superior prognostic accuracy compared with conventional ‌TNM staging‌, with excellent calibration in both the training and validation cohorts. DCA confirmed ‌ the significant net clinical benefits of the nomogram‌. Risk stratification revealed ‌significantly divergent‌ survival rates between the high- and low-risk groups (p < 0.001). Conclusions Our inflammatory-clinicopathological nomogram ‌provides superior prognostic accuracy‌ to conventional TNM staging, ‌enabling‌ personalized risk assessment and treatment optimization for patients with CRC. ‌SIRI integration, as a key biomarker, underscores the critical role of systemic inflammation‌.