Computed tomography has low sensitivity for the diagnosis of early colon cancer

Aim The accuracy of computed tomography (CT) in detecting local invasion (T status) and nodal metastasis (N status) of colon cancer was determined. Method Data on the preoperative CT scan of 153 lesions from 152 patients with colon cancer were reviewed retrospectively. Evaluation included the T stage and N stage of the TNM system. The results were compared with those obtained by histopathological examination of the resected tumour. Results Of the 153 tumours, 117 (76.5%) were correctly classified as Stage T1 and T2 (33 tumours) and Stage T3 and T4 (84 tumours) by CT. The sensitivity and specificity were 70.2% and 79.2%, respectively, and the positive and negative predictive values were 85.7% and 60.0%. When analysed according to the individual T stage (Tx/Tis, T1, 2, 3, 4) and N stage (N0, 1, 2), the kappa coefficient with linear weighting was 0.208 (fair agreement) for T stage and 0.154 (slight agreement) for N stage. The estimation of tumour size showed good agreement with histopathology (Spearman correlation coefficient 0.865). Conclusion CT scanning of colonic cancer showed 75% accuracy in identifying T1 and T2 cancers combined, but gave poor agreement between CT and histopathology for individual T stages.