Contrast-enhanced MRI improves diagnostic accuracy in stage Tis-T1 rectal cancer: a head-to-head comparison with endorectal ultrasound.

Abstract

To investigate whether the addition of contrast-enhanced sequences improves the diagnostic value of MRI in Tis-T1 rectal cancer and to compare its diagnostic performance with that of endorectal ultrasound (ERUS). Patients with pathologically confirmed Tis-T2 rectal cancer who underwent curative resection between January 2020 and December 2023 were enrolled. All patients underwent preoperative MRI (including contrast-enhanced sequencing) and ERUS. Tumor shape and the status of muscularis propria (SMP) were evaluated on T2-weighted images by a radiologist, whereas submucosal enhancing stripe (SES) was assessed on contrast-enhanced MRI. An MRI-based combined model was constructed by integrating tumor shape, SMP, and SES features. ERUS-based tumor staging was performed by an endoscopist. The diagnostic performance of SMP, SES, the combined model, and ERUS in identifying stage Tis-T1 lesions was evaluated. The area under the receiver operating characteristic curves (AUCs) was calculated, and statistical differences were assessed using the DeLong method. In total, 136 patients (mean age: 60 ± 10 years; 78 men) with 138 lesions (82 Tis-T1 and 56 T2 lesions) were enrolled. The AUC values for SMP, SES, the combined model, and ERUS were 0.762 (95% confidence interval [CI]: 0.682-0.830), 0.861 (95% CI: 0.792-0.914), 0.915 (95% CI: 0.856-0.956), and 0.806 (95% CI: 0.730-0.868), respectively. Adding contrast-enhanced MRI feature significantly improved the diagnostic performance over the common approach (combined model vs SMP: AUC difference = 0.154; p < 0.001), and the combined model was also better than ERUS (AUC difference = 0.109; p = 0.003). Incorporating contrast-enhanced MRI improves stage Tis-T1 rectal cancer diagnostic accuracy and outperforms ERUS. Question Can adding contrast-enhanced MRI feature improve the diagnostic performance of MRI in identifying stage Tis-T1 rectal cancer compared to ERUS? Findings The MRI-based combined model incorporating contrast-enhanced and T2WI features achieved the best diagnostic performance (AUC value: 0.915), significantly superior to that of ERUS (p = 0.003). Clinical relevance Incorporating contrast-enhanced MRI offers a more reliable basis for personalized organ-sparing treatment planning and provides a foundation for future clinical practice guidelines.