Multiparametric MRI with pea pod sign and muscularis propria striped enhancement improves T2 vs T3a-b rectal cancer staging accuracy.

Abstract

To evaluate the diagnostic value of a multi-parametric MRI model integrating functional (DWI/DCE) and morphological (T2WI) biomarkers for differentiating T2-stage from T3a-b-stage rectal lesions. 532 rectal cancer patients (T2-stage, n = 319; T3a-b-stage, n = 213) were enrolled in this study. Two radiologists independently evaluated tumor characteristics (status of muscularis propria (SMP), pea pod sign (PPS), depression sign (DS), muscularis propria striped enhancement (MPSE), statue of mesorectal signal (SMS), lymph node involvement, tumor location, and size) at MRI. The associations of clinical and imaging characteristics with stage T2 or T3a-b tumors were assessed, b values were calculated, and predictive models were built for distinguishing T2-stage from T3a-b-stage lesions. Data from 532 patients (mean age, 63 years ± 11 [standard deviation]; 343 men) were evaluated. PPS (b = 4.04; 95% CI: 2.49, 6.54), DS (b = 5.02; 95% CI: 1.91, 13.16), MPSE (b = 8.99; 95% CI: 5.46, 14.79), and distance from the tumor to the anal verge (DTA) (b = 0.99; 95% CI: 0.98, 1.00) were independent factors differentiating T2-stage tumors from T3a-b lesions. The area under the curve (AUC) was 0.85 (95% CI: 0.81-0.88). The nomogram achieved a bootstrapped concordance index of 0.84 and demonstrated good calibration. The multi-parametric MRI model integrating functional (DWI/DCE) and morphological (T2WI) biomarkers showed potential clinical utility in distinguishing T2-stage from T3a-b-stage rectal lesions. Moreover, PPS and MPSE are more accurate features than SMP. Question MRI can improve differentiation between T2 and early T3a-b rectal cancer stages to reduce current overstaging errors and guide optimal treatment decisions. Findings A multi-parametric MRI model integrating pea pod sign and muscularis propria striped enhancement outperforms conventional T2-weighted assessments. Clinical relevance Accurate T2 vs T3a-b distinction prevents unnecessary neoadjuvant chemoradiotherapy for T2 patients while ensuring timely therapy for T3a-b, optimizing treatment outcomes and reducing overtreatment toxicity.