Interobserver Agreement and Radiological-Pathological Concordance of CT Staging in Localized Colon Cancer.

BACKGROUND: Accurate preoperative staging is essential for risk stratification and treatment planning in localized colon cancer (lCC), particularly in the context of emerging neoadjuvant strategies. However, the reproducibility of CT-based classification and its concordance with pathology remain incompletely defined. PATIENTS AND METHODS: We analyzed 175 patients with lCC who underwent baseline contrast-enhanced CT followed by curative-intent surgery. Two independent radiologists assessed clinical tumor (cT) and nodal (cN) stages, with discrepancies resolved by consensus. Interobserver agreement was evaluated using Cohen's kappa. Radiological-pathological (R-P) concordance was assessed for T, N, and overall stage. Multivariable logistic regression analyses were performed to identify predictors of concordance. RESULTS: Interobserver agreement was good for cT classification (κ = 0.77) and excellent for cN classification (κ = 0.94), with overall concordance of 82.9%. R-P concordance was achieved in 78.3% for T staging and 73.7% for N staging, while overall concordance was 57.1%. Most discrepancies reflected adjacent misclassification (29.3%), whereas gross errors were rare (2.3%). CT showed moderate diagnostic performance for T stage (sensitivity 75.7%, specificity 81.6%) and lower sensitivity for nodal involvement (sensitivity 52.3%, specificity 87.3%). Performance varied by tumor location, with higher accuracy in left-sided tumors. Lymphovascular invasion was associated with lower interobserver agreement (odds ratios [OR] 0.34; P = .014), while advanced cT stage predicted reduced R-P concordance for T staging (OR 0.04; P = .004). CONCLUSION: CT classification demonstrates high interobserver reproducibility but only moderate concordance with pathology in lCC. Misclassification may impact clinical decision-making, underscoring the need for improved staging strategies and multidisciplinary integration.