Determination of the Accuracy of Computed Tomography in Staging Primary Rectal Carcinoma and Lymph Node Spread Post Chemoradiation Therapy.

OBJECTIVE

This study aims to evaluate the diagnostic accuracy of multidetector computed tomography (MDCT) in post-chemoradiation restaging of rectal carcinoma. The primary endpoints were T (tumor) and N (nodal) staging accuracy using surgical histopathology as the reference standard. Diagnostic accuracy was defined in terms of sensitivity, specificity, positive predictive value, negative predictive value, and overall concordance. A secondary objective was to assess the role of MDCT in detecting distant metastasis in correlation with intraoperative and available clinical findings.

METHODOLOGY: A prospective analytical observational study was conducted in the Department of Radiodiagnosis at M. S. Ramaiah Hospitals, Bengaluru, from November 2018 to June 2020. Twenty-seven patients with biopsy-proven rectal carcinoma underwent CT imaging of the abdomen and pelvis following chemoradiation and before surgical resection. MDCT-based T (tumor), N (nodal), and M (metastasis) staging were compared with intraoperative assessments and histopathological results. Diagnostic performance was evaluated by calculating sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy.

RESULTS

A total of 27 patients were analyzed, including 16 (59.3%) females and 11 (40.7%) males, with most aged 51-70 years. Bleeding per rectum was the most common symptom in 26 (96.3%) patients, followed by blood in stools in 24 (88.9%) and anemia in 21 (77.8%). Tumors were primarily located in the rectum among 21 (77.8%) patients, and were predominantly adenocarcinomas in 21 (77.8%) patients. Perirectal fat involvement was observed in 18 (66.7%) patients, and regional lymph node invasion in eight (29.6%).

CONCLUSION

MDCT is a reliable modality for staging rectal cancer, particularly for advanced stages (T3-T4), demonstrating high accuracy in assessing tumor extent, nodal involvement, and distant metastases. Its sensitivity for early-stage lesions remains lower than that of MRI, highlighting the complementary role of multimodal imaging in preoperative evaluation.