Predictive Parameters in Magnetic Resonance Imaging for Tumor Regression after Neoadjuvant Chemoradiotherapy Applied for Rectal Cancer

To date, magnetic resonance imaging (MRI) plays a critical role in the management of rectal cancer. Although neoadjuvant chemoradiotherapy (nCRT) is a gold standard approach in advance to surgical management, it might alter the tissue texture, affecting MRI findings applied for decision-making in a procedural approach.

The current study aimed to assess the predictive parameters in MRI associated with response to nCRT in rectal cancer.

The current cross-sectional study has been conducted on 50 patients with rectal cancer who were candidates for nCRT during 2020- 21. Data including tumor markers and MRI parameters including tumor signal, tumor stage (TMN), lymph node involvement, mesorectal fascia (MRF), extramural venous invation (EMVI), peritoneal reflection invasion and tumor size were gathered at baseline and within 4-6 weeks after nCRT. The predictive factors for response to nCRT were evaluated using tumor regression grade (TRG) and TNM staging.

Tumor size (P<0.001), MRI signal intensity (P=0.038), tumor appearance in diffuse weighted imaging (DWI) (P<0.001), tumor stage (P<0.001), lymph node involvement (P<0.001), MRF (P<0.001), EMVI (P<0.001), and peritoneal reflection invasion (P<0.001) remarkably improved in post-nCRT assessments. Tumor size was associated with 3.75 (95%CI: 1.61-8.72) and 2.64 (95%CI: 1.40-4.97) folds, and lymph node involvement was associated with 77% (95%CI: 0.21-15.02) and 60% (95%CI: 0.21- 11.96) increased probability of response to treatment based on TRG and TNM, respectively.

Based on the findings of this study, nCRT could remarkably improve adenocarcinoma of rectal cancer-related laboratory and imaging parameters; however, tumor size and lymph node involvement were the only predicting factors for response to nCRT.