Effectiveness of High-resolution T2-weighted Mri in Restaging Rectal Cancer After Neoadjuvan Chemoradiotherapy

Abstract

Objective: The technical success of high-resolution T2-weighted magnetic resonance imaging (hT2W-MRI) sequence in restaging locally advanced rectal cancer treated with neoadjuvant chemoradiotherapy (nCRT) was investigated. Materials and methods: Nineteen patients with an age mean 56 ( range of 37-76) who received nCRT for rectal cancer, had MRI for the rectum and underwent surgical operation between 2020-2022 were included in the study. MRI results were compared with relevant histopathological studies after definitive surgery . Results: hT2W-MRI correctly predicted all tumors with pathological stage T3 100% (5/5). hT2W-MRI predicted correctly in 3 of 4 patients with pathological stages T4a and T4b (75%). Considering lymph node positivity, the prediction rate of hT2W-MRI was 42.1%(8/19). hT2A-MRI correctly predicted all tumors with circumferential resection margin (CRM), peritoneal reflection involvement, and extramural venous invasion (EMVI). The success of hT2W-MRI in predicting the pathological response (residual tumor) was high (89.5%, 17/19). Conclusion: Staging of rectal cancer after nCRT is important for treatment planning. Functional assessment with diffusion-weighted MRI and perfusion MRI play a role in predicting tumor aggressiveness, likelihood of response to treatment, and size of tumor remaining after treatment. An accurate and practical radiological identification is important, as the findings on MRI after nCRT are related to the patient's prognosis and survival, and the tumor stage is based on the depth of invasion of the rectal wall and the involvement of adjacent organs. It would be beneficial to include the hT2A-MRI sequence in standard pelvic MRI examination sequences in staging of rectal cancer after nCRT and in demonstrating the presence of residual tumor.