Accuracy of MRI in Predicting Circumferential Resection Margin and Mesorectal Fascia Involvement for Locally Advanced Rectal Cancer Keeping Operative Findings as a Gold Standard

Background: Locally advanced rectal cancer requires precise preoperative staging in order to allow perioperative planning and the best oncological outcomes. MRI has become the norm in the evaluation of circumferential resection margin and involvement of the mesorectal fascia. Thorough analysis of these parameters assists in the decision regarding neoadjuvant therapy and provides an estimate of the risk for local recurrence. Objective: To determine the accuracy of magnetic resonance imaging in determining the circumferential resection margin involvement and mesorectal fascia involvement for patients with locally advanced rectal cancer, while using operative findings as the gold standard. Study Design: Cross-sectional validation study. Duration and Place of Study: The study was conducted from June to November 2024 at the Department of Diagnostic Radiology, Shaikh Zayed Hospital, Lahore. Methodology: A total of 200 patients aged 20–70 years undergoing surgery for rectal carcinoma were enrolled. High-resolution pelvic MRI was performed using a 1.5T scanner, and findings regarding CRM and MRF involvement were recorded. Surgical assessment served as the gold standard. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were calculated. Results: The mean age of patients was 47.23 ± 9.22 years with a mean symptom duration of 6.50 ± 3.08 months. MRI demonstrated a sensitivity of 85.90%, specificity of 90.70%, and diagnostic accuracy of 89.00%. PPV and NPV were 83.60% and 92.10%, respectively. Diagnostic performance was higher in females (96.00% accuracy), younger patients (≤40 years), and those with shorter symptom duration (≤6 months). Conclusion: MRI is a highly accurate and reliable modality for preoperative assessment of CRM and mesorectal fascia involvement in locally advanced rectal cancer.