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.