Diagnostic Accuracy of High-Resolution Multidetector CT Compared to MRI in Local Staging of Rectal Cancer: A Prospective Study

Background: Magnetic resonance imaging (MRI) remains the gold standard for local staging of rectal cancer due to its superior soft-tissue contrast. However, its limited accessibility, high cost, and potential for delay in imaging workflows, particularly in low-resource settings, necessitate the exploration of alternative modalities. Recent advances in multidetector computed tomography (MDCT) allow for high-resolution multiplanar imaging that may be suitable for local rectal staging Purpose: To evaluate the diagnostic accuracy of high-resolution MDCT for local staging of rectal cancer, compared to MRI Methods: This prospective study included 40 patients with biopsy-confirmed rectal carcinoma. All underwent pelvic MRI and contrast-enhanced MDCT with an optimized early venous phase protocol. Imaging findings were compared across T stage, N stage, circumferential resection margin (CRM) involvement, and detection of distant metastases. MRI served as the reference standard. Agreement between modalities was assessed using weighted kappa statistics; diagnostic accuracy parameters were calculated for MDCT Results: MDCT demonstrated excellent concordance with MRI for T3–T4 staging (κ = 0.82), with 100% sensitivity and 95% overall accuracy. CRM assessment showed perfect agreement between modalities (κ = 1.0). For nodal staging, MDCT achieved a kappa value of 0.73, with a sensitivity of 100% and specificity of 77%. Distant metastases were detected in 4 patients (10%) by MDCT but missed on MRI. MDCT over-staged early-stage tumors in several cases Conclusion: High-resolution MDCT, when performed with a standardized protocol, provides excellent diagnostic accuracy for local staging of advanced rectal cancer and offers additional benefit in systemic assessment. It represents a valuable alternative when MRI is unavailable or delayed.