Utility of the Aortic-Lesion-Attenuation-Difference (ALAD) and Peak Early-Phase Enhancement Ratio (PEER) to differentiate benign from malignant renal masses.

INTRODUCTION

To evaluate the utility of the Aorta-Lesion-Attenuation-Difference (ALAD) and Peak Early-phase Enhancement Ratio (PEER) on contrast-enhanced computed tomography (CT) to differentiate between the appearances of chromophobe renal cell carcinoma, clear cell renal cell carcinoma, and oncocytoma.

MATERIAL AND METHODS

ALAD and PEER values were retrospectively measured by a reviewer from 119 patients with surgically resected renal masses (chromophobe renal cell carcinoma n = 29, clear cell renal cell carcinoma n = 28, and oncocytoma n = 62). The ALAD value is expressed as: ALAD = Hounsfield Units aorta - Hounsfield Units mass. PEER is expressed as (Hounsfield Units contrast tumor - Hounsfield Units non-contrast tumor):( Hounsfield Units contrast cortex - Hounsfield Units non-contrast cortex).

RESULTS

The ALAD median was 27.6 for oncocytomas, 68.5 for chromophobe renal cell carcinoma, and 55.4 for clear cell renal cell carcinoma. A significant difference between ALAD values of oncocytoma and chromophobe renal cell carcinoma was observed in the nephrographic (area under the ROC curve 0.92) and excretory phases (area under the ROC curve 0.95). The PEER median was 0.74 for oncocytomas and 0.37 for chromophobe renal cell carcinoma. The PEER values significantly differed while comparing oncocytomas and chromophobe renal cell carcinoma in the nephrographic and excretory phases.

CONCLUSIONS

Preoperative contrast-enhanced CT ALAD and PEER values both significantly differentiate between chromophobe renal cell carcinoma and oncocytoma. PEER may be more effective in contrast-enhanced CT scans lacking distinct phases.