The Role of MRI in the Preoperative Staging of Rectal Cancer: Ten-year Experience from a Single Tertiary Center

Accurate preoperative staging of rectal cancer (CRC) guides treatment decisions, particularly regarding neoadjuvant chemoradiotherapy. Although magnetic resonance imaging (MRI) is recommended for local staging, questions persist regarding whether T stage or circumferential resection margin (CRM) involvement is the stronger predictor of treatment necessity. This study evaluated ten years of institutional experience to determine whether MRI-based CRM assessment provides superior prognostic guidance compared to tumor-node-metastasis (TNM) staging alone.

Between March 2014 and July 2023, 659 patients underwent surgery for histologically confirmed rectal adenocarcinoma; 258 received preoperative MRI and computed tomography (CT) imaging. After applying exclusion criteria (neoadjuvant therapy prior to surgery, transanal endoscopic procedures, patient refusal, contraindications), 114 patients undergoing primary surgical resection comprised the study cohort. MRI- and CT-derived T and N stages and CRM involvement were compared with definitive histopathological findings using chi-squared, Fisher's exact, independent t-tests, Mann-Whitney U-tests, and diagnostic accuracy calculations.

MRI correctly predicted pathological T (pT) stage in 47.4% of cases versus CT in 48.2% (p=0.895), indicating no significant difference. CT more frequently underestimated T stage (33.3%), whereas MRI more often overestimated (36.8%, p<0.001). MRI demonstrated higher sensitivity for nodal metastasis (74% vs. 62%), although specificity was lower (39.1% vs. 54.7%). Critically, MRI correctly identified all seven patients with pathological circumferential resection margin (pCRM) ≤1 mm (6.14% of cohort), achieving 100% concordance. Local recurrence occurred in nine patients (7.9%) during follow-up; all received primary surgery based on negative mesorectal fascia (MRF) status on MRI.

MRI reliably predicts CRM involvement and MRF status, serving as a key determinant for neoadjuvant chemoradiotherapy decisions. In patients with T3 tumors and negative MRF status on MRI, primary resection remains oncologically safe, avoiding unnecessary chemoradiotherapy-related morbidity while maintaining acceptable recurrence rates comparable to literature data.