Renal Cell Carcinoma: Role of MR Imaging in the Assessment of Muscular Venous Branch Invasion

Abstract

To assess diagnostic performance and interreader agreement of tumor-to-sinus distance measurements and visual assessment of renal sinus fat invasion at T2-weighted magnetic resonance (MR) imaging as predictors of muscular venous branch invasion (MVBI) in patients with renal cell carcinoma (RCC). The institutional review board approved this retrospective study and waived the informed consent requirement. The study was HIPAA compliant. A total of 186 consecutive patients underwent preoperative 1.5-T MR imaging; 188 RCCs were identified. Blinded to histopathologic information, two readers independently measured the tumor-to-sinus distance and assessed renal sinus fat invasion on transverse and coronal T2-weighted MR images. Interreader agreement (intraclass correlation coefficient, Cohen κ) and performance characteristics of imaging tests were calculated. Histopathologic findings served as the standard of reference. Histopathologic findings indicated MVBI in 35% (66 of 188) of tumors. At imaging, all tumors with MVBI had a tumor-to-sinus distance of 0 mm. All tumors with renal sinus fat invasion at imaging had MVBI. Sensitivity and specificity for the detection of renal sinus fat invasion were 100% (95% confidence interval [CI]: 92%, 100%) and 94% (95% CI: 89%, 98%). In the absence of renal sinus fat invasion at imaging, a tumor-to-sinus distance of 0 mm was associated with MVBI in 21% (18 of 86) of cases. Interreader agreement for quantitative (intraclass correlation coefficient = 0.92; 95% CI: 0.89, 0.94) and qualitative (κ = 0.89; 95% CI: 0.81, 0.96) assessments was excellent. Tumor-to-sinus distance measurements and the assessment of renal sinus fat invasion at T2-weighted MR imaging can be used reliably to rule out MVBI in patients with RCC.