Predictive value of rectal MRI variables for pathological complete response in locally advanced rectal cancer following neoadjuvant chemoradiotherapy.

Abstract

Purpose: To evaluate the predictive value of MRI-determined variables for pathological complete response (pCR) in locally advanced rectal cancer (LARC) patients following neoadjuvant chemoradiotherapy (NCRT).

Methods: Clinical data were collected from patients who received NCRT between January 2019 and 2022. Patients with rectal adenocarcinoma, cT3-4N0, or TanyN1-2 were included. pCR was defined pT0N0. Patients were divided into pCR and non-pCR group. Logistic regression analysis was performed to identify factors associated with pCR. A nomogram model was constructed to validate its predictive ability and accuracy.

Results: A total of 585 patients were identified, with 144 (24.6%) in the pCR group and 441 (75.4%) in the non-pCR group. Patients with mrT2-3 (OR 6.41, P < 0.001), mrN0 (OR 2.17, P < 0.001), circumferential occupation range < 1/2 cycles (OR 2.11, P < 0.001), tumor vertical diameter < 36 mm (OR 2.10, P < 0.001), negative mesorectal fascia (OR 3.21, P < 0.001), and extramural vascular invasion (OR 5.68, P < 0.001) were more likely to achieve higher pCR rates. Logistic regression analysis revealed that mrT2-3 (OR 3.50, P < 0.001), tumor vertical diameter < 36 mm (OR 2.57, P < 0.001), and negative extramural vascular invasion (OR 4.03, P < 0.001) were independent protective factors for pCR. A nomogram was developed to predict pCR, achieving a C-index of 0.778.

Conclusion: Patients with mrT2-3, tumor vertical diameter < 36 mm, and negative extramural vascular invasion are more likely to achieve pCR after NCRT.