C-reactive Protein-to-Albumin Ratio as a Superior Inflammatory Marker in Resected Biliary Tract Cancer: Development...

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.

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.

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.

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.