Validity of Magnetic Resonance Imaging in Pre-Operative Assessment of Rectal Cancer

Background: Accurate pre-operative staging of rectal cancer is pivotal for neoadjuvant selection and surgical planning.Aims: They were to evaluate the diagnostic performance of pelvic MRI (including DWI/ADC) for T/N staging and circumferential resection margin (CRM) and to explore ADC as a biomarker of aggressiveness.Methods: Prospective study of 65 biopsy-proven rectal adenocarcinoma patients. Females were 61.5% (mean age was 47.2±14.4 years). The patients undergone 1.5-T MRI with high-resolution T2, DWI (b=0/500/1000 s/mm²), and contrast enhancement. Two blinded readers recorded T stage, N stage, CRM status, and mean tumor ADC (three ROIs). Histopathology was the reference.Results (interpreted): Mean ADC was 0.752±0.119×10⁻³ mm²/s (0.5–1.0). MRI called CRM positive in 36.9% versus 24.6% pathologically (κ=0.432, p=0.010), yielding sensitivity 75.0%, specificity 75.5%, accuracy 75.4%, NPV 90.2%, PPV 50.0%—supporting MRI as a strong rule-out test for involved CRM. For T staging, agreement was modest (κ=0.382, p=0.036) with sensitivity 68.4%, specificity 72.5%, accuracy 70.2%; MRI tended to upstage T2 as T3. N staging showed weak, non-significant agreement (κ=0.200, p=0.116) with sensitivity 62.8%, specificity 67.2%, accuracy 68.4%. Lower ADC values were significantly associated with sphincteric invasion, extramural invasion, mesorectal fat stranding, mesorectal fascia invasion, peritoneal involvement, pelvic sidewall affection, and extra-mesorectal adenopathy (all p<0.05).Conclusion: Pre-operative MRI offers excellent NPV for CRM and moderate accuracy for T staging, while N staging remains challenging. Quantitative ADC correlates with multiple invasive features and may refine risk stratification within multidisciplinary care.