Advanced diffusion-weighted imaging biomarkers for non-invasive assessment of tumor microenvironment in rectal cancer: restricted spectrum imaging

To explore the heterogeneity of the rectal cancer microenvironment (TME) using restricted spectrum imaging (RSI) and investigate its association with tumor stroma and Ki67 as key histopathologic indicators.

In this prospective study, 66 patients with rectal cancer underwent pretreatment MRI with RSI. The optimal model format was determined by Bayesian Information Criterion (BIC). RSI3-derived parameters (RSI₃-C1, RSI₃-C2, RSI₃-C3) and ADC values were measured and correlated with stroma status, Ki67 expression, and clinicopathological features. The diagnostic performance of these quantitative imaging biomarkers was assessed using receiver operating characteristic (ROC) analysis.

The three-compartment RSI model (RSI₃) was optimal for characterizing rectal cancer (△BIC = 0). RSI₃-C1, RSI₃-C2, and RSI₃-C3 showed significant differences between low-stroma and high-stroma groups (P < 0.05). RSI₃-C2 exhibited the highest accuracy in characterizing stroma status (AUC = 0.800, sensitivity = 79.2%, specificity = 71.4%). All RSI₃ parameters and ADC values differed significantly between low-Ki67 and high-Ki67 groups (P < 0.05). RSI₃-C1 demonstrated the highest accuracy in characterizing Ki67 status (AUC = 0.824, sensitivity = 90.0%, specificity = 69.4%). Significant differences were observed in RSI₃-C3 and ADC values for tumor differentiation (P < 0.05). RSI₃-C3 showed the highest accuracy in characterizing differentiation status (AUC = 0.721, sensitivity = 66.7%, specificity = 83.3%).

RSI₃-derived parameters show potential as non-invasive biomarkers for evaluating TME in rectal cancer. This innovative approach may improve decision-making, leading to better patient outcomes in rectal cancer management.