Radiological Markers in Locally Advanced Rectal Cancer

This study investigates the prognostic role of diffusion-weighted MRI (DWI), using the Likert Score and other radiological markers, in patients with locally advanced rectal cancer (LARC) undergoing total neoadjuvant therapy (TNT) followed by radical surgery. The study cohort consists of 179 patients who received TNT between 2009 and 2022 at our institution. Inclusion criteria required patients to have biopsy-confirmed stage II-III LARC, available MRI at both staging and restaging time points, and completion of the TNT protocol.

The TNT regimen included up to three cycles of modified XELOX chemotherapy (oxaliplatin and capecitabine), with the first cycle administered as induction chemotherapy and the remaining two cycles administered concurrently with radiotherapy (total dose: 46.2 Gy in 18 fractions). Surgical resection was performed at a median of 11 weeks post-radiotherapy, with adjuvant chemotherapy administered based on histopathology findings.

MRI acquisition was standardized using a 1.5-T scanner, with DWI sequences applied to assess key prognostic markers, including extramural venous invasion (EMVI), tumor deposits (TDs), and mesorectal fascia invasion (MFI). The Likert Score, a five-point grading system based on DWI findings, was applied to restaging MRI to stratify treatment response, with scores of 0-2 indicating a favorable response and 3-4 indicating a poor response.

The study's primary objective is to evaluate the impact of the Likert Score on overall survival (OS) and time to progression (TTP). Secondary objectives include assessing the prognostic significance of EMVI, TDs, and MFI in predicting OS and TTP. The statistical analysis will include Kaplan-Meier survival curves to estimate OS and TTP, stratified according to the presence/score of radiological markers, Cox proportional hazards regression to assess the impact of prognostic factors on survival outcomes, Fisher's exact test to evaluate associations between categorical variables, and Cohen's Kappa to measure interobserver agreement in MRI assessments..

This study aims to refine MRI-based prognostic assessment tools to enhance personalized treatment strategies for rectal cancer. Findings from this research may support the integration of DWI-based Likert Score evaluation into clinical practice to improve risk stratification and treatment decision-making in patients with LARC undergoing TNT. The follow-up period extends until July 31, 2024, ensuring a comprehensive analysis of long-term outcomes.