Rectal cancer: CT local staging with histopathologic correlation

Background: Many surgical options, eventually combined with neoadjuvant the rapy, are available for the treatment of rectal cancer. Preoperative stagin g is essential to plan the correct treatment. Our aim was to evaluate the d iagnostic accuracy of computed tomography (CT) in the local staging of rect al cancer. Methods: Between February 1995 and May 2000, 105 patients (65 male, 40 fema le; mean age = 58, range = 36-88 years) after preoperative locoregional CT staging underwent rectal resection for rectal cancer. In all patients, radi ologic T and N staging was verified with pathologic examination of excised specimens. Patients were examined after air insufflation of the ampulla, du ring intravenous contrast injection; analysis of the rectoanal region was p erformed with thin (3-5 mm) contiguous slices. For T staging, Tis-T2, T3, a nd T4 groups were considered. For N staging, two groups of patients were co nsidered: in 52 patients, N+ stage was attributed to all visible lymph node s; in the other 53 patients, only lymph nodes >5 mm were recorded as N+. Results: Pathologic examination showed 61 T1-T2, 40 T3, and four T4 tumors; CT examination correctly identified 50 T1-T2 (81.9%), 33 T3 (82.5%), and t hree T4 (75%) lesions. With regard to N stage, pathologic examination in th e first group (52 patients) showed only 11 cases of lymph node involvement. CT examination detected all 11 true-positive lymph nodes but overestimated 30 false-positive cases. In the second group (53 patients), pathology show ed 26 cases of nodal involvement: CT examination identified 23 true-positiv e, 19 true-negative, eight false-positive, and three false-negative lymph n odes. Conclusion: CT correctly staged 86 (82%) of 105 lesions. Overestimation occ urred in T2 patients (11 of 61, 18%) and underestimation in T3 patients (se ven of 33, 21%), in accordance with other reports dealing with superior acc uracy of endorectal ultrasonography in local staging of early disease. Conv ersely, the criterion we suggest for evaluating metastatic perirectal lymph nodes (diameter > 5 mm) provided 79.2% diagnostic accuracy, 88.5% sensitiv ity, and 86.5% negative predictive value. This can be useful in those patie nts in whom prompt surgery, soon after radiochemotherapy in the case of nod al involvement, may likely be curative. With further improvement with spira l CT in local staging and nodal involvement, a larger number of transanal c urative resections can be predicted.