MRI-guided risk stratification for neoadjuvant immunotherapy in rectal cancer

BackgroundNeoadjuvant therapy improves local control and tumor downstaging in locally advanced rectal cancer (LARC) and is now the standard of care. However, reliable tools for identifying patients who may show different response patterns to neoadjuvant immunotherapy-containing treatment, particularly MRI-based risk stratification systems, remain limited.Materials and methodsThis retrospective study included 135 patients with locally advanced rectal cancer, who were classified into a neoadjuvant immunotherapy plus chemoradiotherapy group (nICRT, n = 43) and a neoadjuvant chemoradiotherapy group (nCRT, n = 92).

The nICRT group received short-course radiotherapy plus CAPOX and sintilimab, whereas the nCRT group received either short-course radiotherapy plus CAPOX or long-course chemoradiotherapy plus CAPOX. All patients underwent baseline pelvic MRI, including high-resolution T2-weighted, diffusion-weighted, and T1-weighted sequences.

Evaluated variables included mrT stage, mrN stage, mrEMVI status, mrMRF involvement, tumor length, and clinical laboratory indices. Interobserver agreement was assessed using Cohen’s kappa statistics, and factors associated with pathological complete response (pCR) were analyzed using group comparisons and logistic regression analyses.

Fisher’s exact test was used for subgroup comparisons.