Diagnostic Effectiveness of High-Resolution T2- Weighted Magnetic Resonance Imaging in Restaging Rectal Cancer After Neoadjuvant Chemoradiotherapy

Objective: The staging of rectal cancer after neoadjuvant chemoradiotherapy (nCRT) influences treatment planning. It is critical to have an accurate and practical radiological identification. The technical success of a high- resolution T2-weighted magnetic resonance imaging (hT2W-MRI) sequence in restaging locally progressed rectal cancer treated with nCRT was investigated in this study. Materials and Methods: The study included 19 patients (mean age=56, range=37-76) who had rectal cancer surgery between 2020 and 2022, a rectum MRI, and nCRT. Following surgery, MRI data were compared to relevant histological studies. Results: hT2W-MRI correctly predicted all cancers with pathological stage T3 (100%, 5/5). Three out of four patients (75%) with pathological stages T4a and T4b were correctly predicted by hT2W-MRI. When lymph node positivity was taken into account, the hT2W-MRI prediction rate was 42.1% (8/19). All tumors with a circumferential resection margin (CRM), peritoneal reflection involvement, and extramural venous invasion were appropriately predicted by hT2W-MRI. hT2W-MRI had a good success rate in predicting pathological response (residual tumor) (89.5%, 17/19). Conclusion: Incorporating the hT2W-MRI sequence into routine pelvic MRI examination sequences can be beneficial for detecting residual tumor and staging rectal cancer after nCRT. Keywords: Advanced rectal cancer, circumferential resection margin, extramural venous invasion, magnetic resonance imaging, neoadjuvant chemoradiotherapy