Abstract
BACKGROUND/AIM: Consensus on the most informative inflammatory marker for prognosis in biliary tract cancer (BTC) is lacking. The aim of this study was to comprehensively evaluate preoperative inflammatory indices and develop a prognostic nomogram complementary to TNM staging. PATIENTS AND METHODS: A total of 247 patients with resected BTC were retrospectively analyzed. Eight inflammatory indices, including prognostic nutritional index (PNI) and C-reactive protein-to-albumin ratio (CAR), were assessed alongside non-TNM clinicopathological variables. Least absolute shrinkage and selection operator (LASSO) regression identified overall survival-associated variables for multivariable Cox regression and nomogram construction. Model performance was evaluated using Kaplan-Meier analysis, concordance (C-) index, time-dependent area under the curve (tdAUC), decision curve analysis (DCA), and calibration plots, with bootstrap validation. RESULTS: LASSO selected PNI and CAR; CAR remained independently significant. The nomogram incorporated CAR and five clinicopathological factors: body mass index ≥25 kg/m2, carbohydrate antigen 19-9 >37 U/ml, moderate/poor differentiation, perineural invasion, and residual tumor status. Patients were stratified by nomogram score into four risk groups showing distinct survival differences. Notably, 50.6% of TNM Stage I-II were reclassified as higher risk, 16.1% of Stage III-IV as lower risk. The nomogram achieved C-index 0.722 versus 0.659 for TNM (p=0.022), with superior tdAUCs, clinical benefit on DCA, and good calibration. Consistent prognostic performance was observed across BTC subtypes and TNM stages. CONCLUSION: CAR demonstrated superiority over other inflammatory indices in resected BTC. This CAR-based nomogram complements TNM staging, offering enhanced prognostic stratification for patients with heterogeneous outcomes within the same anatomical stage.