Study on Predicting Microsatellite Instability in Rectal Cancer Using T2 Mapping Combined with ADC Value

Objective: To investigate the feasibility of T2 mapping combined with apparent diffusion coefficient (ADC) value for preoperatively predicting microsatellite instability (MSI) status in rectal cancer. Methods: This retrospective study included 152 patients with pathologically confirmed rectal cancer (40 MSI, 112 microsatellite stable [MSS]). All patients underwent MRI including T2 mapping and diffusion-weighted imaging (DWI). Tumor T2 and ADC values were measured and compared. A combined prediction model was constructed using multivariate logistic regression with SMOTE oversampling and L2 regularization. Diagnostic performance was evaluated using receiver operating characteristic (ROC) curve analysis, with model stability assessed via 10-fold cross-validation and Bootstrap resampling (1000 times). Results: The MSI group had a significantly lower T2 value (92.18 ± 7.21 ms vs. 99.47 ± 7.85 ms, p<0.001) and a higher ADC value (1.06 ± 0.18 vs. 0.91 ± 0.19 ×10−3 mm2/s, p<0.001) compared to the MSS group. The AUC for predicting MSI status was 0.865 for T2 value and 0.741 for ADC value. The combined model significantly improved the AUC to 0.915 (95% CI: 0.865-0.965), with a sensitivity of 82.5% and specificity of 89.3%. The model demonstrated excellent stability (Bootstrap mean AUC=0.913). Conclusion: T2 mapping combined with ADC value provides a reliable, non-invasive method for preoperatively predicting MSI status in rectal cancer. The diagnostic efficacy of the combined model is superior to either parameter alone, showing high potential for clinical translation to guide precision therapy.