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

Abstract

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.

Keywords: Colonic polyps/diagnosis; colonic polyps/pathology; colonic polyps/radiology.