Comparative effectiveness of two abbreviated rectal MRI protocols in assessing tumor response to neoadjuvant chemoradiotherapy in patients with rectal cancer

Abstract

The present study aimed to compare the effective‑ ness of two abbreviated magnetic resonance imaging (MRI) protocols in assessing the response to neoadjuvant chemora‑ diotherapy (CRT) in patients with rectal cancer. Data from the examinations of 62 patients with rectal cancer who underwent neoadjuvant CRT and standard contrast‑enhanced rectal MRI were retrospectively evaluated. Standard contrast‑enhanced T2‑weighted imaging (T2‑WI), post‑contrast T1‑weighted imaging (T1‑WI) and diffusion‑weighted imaging (DWI) MRI, as well as two abbreviated protocols derived from these images, namely protocol AB1 (T2‑WI and DWI) and protocol AB2 (post‑contrast fat‑suppressed (FS) T1‑WI and DWI), were assessed.Measurements of lesion length and width, lymph node short‑axis length, tumor staging, circumferential resection margin (CRM), presence of extramural venous invasion (EMVI), luminal mucin accumulation (MAIN), mucinous response, mesorectal fascia (MRF) involvement, and MRI‑based tumor regression grade (mrTRG) were obtained. The reliability and compatibility of the AB1 and AB2 protocols in the evaluation of tumor response were analyzed. The imaging performed according to the AB1 and AB2 protocols revealed significant decreases in lesion length, width and lymph node size after CRT. These proto‑ cols also showed reductions in lymph node positivity, CRM,MRF, EMVI.Furthermore, both protocols were found to be reliable in determining lesion length and width. Additionally, compliance was observed between the protocols in deter‑ mining lymph node size and positivity, CRM involvement, and EMVI after CRT. In conclusion, the use of abbreviated MRI protocols, specifically T2‑WI with DWI sequences or post‑contrast FS T1‑WI with DWI sequences, is effective for evaluating tumor response in patients with rectal cancer following neoadjuvant CRT.The AB protocols examined in this study yielded similar results in terms of lesion length and width, lymph node positivity, CRM involvement, EMVI, MAIN, and MRF involvement.