Radiopathological Correlation in Locally Advanced Rectal Cancer After Neoadjuvant Treatment.

Objectives: Magnetic resonance imaging plays a pivotal role in the management of locally advanced rectal cancer. This study aims to assess the correlation between magnetic resonance tumor regression grade and pathological tumor regression grade following neoadjuvant therapy in patients with locally advanced rectal cancer. Material and Methods: A retrospective analysis was conducted on 97 patients diagnosed with LARC (T3-T4 or any T stage with regional lymph node involvement) who underwent neoadjuvant chemoradiotherapy followed by radical surgery between 2014 and 2020. The correlation between mrTRG and pTRG was evaluated primarily using the weighted Kappa statistic. Additional clinical and imaging data were collected for a comprehensive analysis. Results: The median interval between completion of neoadjuvant therapy and restaging MRI was 40 days, with a median of 69 days from completion of chemoradiotherapy to surgery. The weighted Kappa was 0.27, indicating fair agreement between mrTRG and pTRG. MRI demonstrated a sensitivity of 52.1% and specificity of 81.6% for detecting a good response (pTRG 1-2). For identification of a complete response (pTRG 1), MRI showed a sensitivity of 10% and specificity of 98.7%. Conclusions: The correlation between mrTRG and pTRG shows fair agreement. Although MRI alone may not be sufficient to reliably predict pathological response, its high specificity suggests it can be a useful tool to confirm good and complete responses. Therefore, MRI should be integrated with other diagnostic methods, such as endoscopy and digital rectal examination, especially in organ preservation strategies. Moreover, MRI retains potential as a prognostic factor to guide clinical decision-making in LARC.