Conventional CT for the prediction of an involved circumferential resection margin in primary rectal cancer

To determine the accuracy of conventional computed tomography (CT) scan in the preoperative prediction of an involved circumferential resection margin (CRM) in primary rectal cancer.

125 patients with biopsy-proven adenocarcinoma of the rectum underwent CT of the abdomen before undergoing total mesorectal excision. Scans were scored by three observers, differing in experience. The main outcome was yes/no involvement of the CRM. Histology was taken as reference standard.

For the most experienced observer, observer A, sensitivity was 46.7% and specificity 92.6%. For observer B, sensitivity was 46.7% and specificity 89.5%. For the least experienced observer C, sensitivity was 43.3% and specificity 92.6%. Inter-observer variability was good between observers A and B (kappa 0.648), B and C (kappa 0.648), and intermediate between A and C (kappa 0.542). Discrepancies occurred in a total of 34 patients; 25 had a CT scan of low technical quality, 10 an anteriorly located distal tumor.

Conventional CT scan lacks sensitivity for a clinical use in the preoperative assessment of an involved CRM in primary rectal cancer. Modern multislice spiral CT will probably resolve some of the problems of conventional CT; however, further research is needed to establish its role.