Value of Noncontrast-Enhanced Vessel Wall MRI in Longitudinal Venous System Invasion Before Robot-Assisted Radical Nephrectomy

Objectives: To explore the value of vessel wall MRI (VW-MRI) in the preoperative assessment of T3 renal-cell carcinoma (RCC) with varying degrees of longitudinal venous system invasion. Materials and Methods: Patients with RCC with pathological T3 stage between January 2016 and December 2023 were included in this retrospective study. All the patients underwent contrast-enhanced CT (CECT), conventional MRI (con-MRI) or VW-MRI. Images were independently and blindly evaluated at 4-week intervals by three readers. The pathological features reported in the pathological report, combined with clinical data, were used as the reference standards. The incremental value was calculated using net reclassification improvement (NRI) and integrated discrimination improvement. Results: Eighty-two T3 RCC patients (median age, 65 years) were enrolled. The accuracy of T staging in CECT (n = 59), con-MRI (n = 49), and VW-MRI (n = 30) was 69.5%, 71.4%, and 93.3%, respectively. VW-MRI had a statistically incremental value for CECT in the preoperative evaluation of T3a-c stages (T3a: NRI = 0.066, p = 0.04. T3b: NRI = 0.085, p = 0.02. T3c: NRI = 0.178, P = 0.02), especially in renal pelvicaliceal invasion (NRI = 0.154, p = 0.04) and vena cava wall invasion (NRI = 0.263, p = 0.01). Besides, statistically significant preoperative incremental effects were obtained in the assessment of T3a-c stages (T3a: NRI = 0.264, p = 0.01. T3b: NRI = 0.373, p = 0.03. T3c: NRI = 0.202, p = 0.045), renal vein invasion (NRI = 0.630, p = 0.03), and vena cava wall invasion (NRI = 0.185, p = 0.02) when added VW-MRI into con-MRI. VW-MRI changed 24% (4/27) of the previous CECT and con-MRI-based surgical plan. Conclusion: VW-MRI added a preoperative value for evaluating T stage of T3 RCC, especially in the evaluation of renal vein invasion and vena cava wall invasion.