Preoperative differentiation of chromophobe renal cell carcinoma from oncocytoma: Aorta-lesion-attenuation difference on multiphasic multidetector computed tomography.

Abstract

627 Background: Differentiation of benign oncocytoma from chromophobe renal cell carcinoma (chRCC) remains a challenge. This study aimed to investigate whether Aorta-lesion-attenuation difference (ALAD) on multiphasic multidetector CT scan (MDCT) can aid to distinguish oncocytoma from chRCC. Methods: This IRB-approved, HIPAA-compliant study consisted MDCT of 111 patients with pathologically proven chRCC (N: 37) or oncocytoma (N: 74). Regions of interest (ROIs) were placed over the renal mass and Aorta on the same axial MDCT slice of un-enhanced (UE), corticomedullary (CM), nephrographic (NP) and excretory (EX) phases. ROIs were devoid of calcification, necrosis and hemorrhage in lesion or atherosclerotic plaque in Aorta. The difference between Aorta and renal mass Hounsfield unit was calculated in all available phases. SPSS v.18 was used to draw receiver-operating characteristic (ROC) curve to calculate accuracy and optimal cutoff values for differentiation of chRCC from oncocytoma. Results: Mean ALAD was significantly higher in chRCC compared to oncocytoma in CM(P: 0.04), NP (P<0.01) and EX (P<0.01) phases. The area under the curves for ALAD in UE, CM, NP and EX phases were 0.47 (95% CI: 0.36- 0.59, p: 0.68), 0.64 (95% CI: 0.51-0.77, p: 0.03), 0.87 (95% CI: 0.79- 0.95, p< 0.01) and 0.80 (0.70-0.90, P<0.001), respectively. ALAD threshold of 19 in nephrographic phase had sensitivity and specificity of 79% and 78%, respectively, for differentiation of chRCC from oncocytoma. Conclusions: ALAD measured in the nephrogenic phase showed the highest accuracy for differentiation of chRCC from oncocytoma on multidetector CT scan. If validated prospectively, ALAD may act as a useful imaging biomarker to distinguish chRCC from oncocytoma.