1976. Differentiation of Chromophobe Renal Cell Carcinoma from Oncocytoma Using Aorta-Lesion-Attenuation-Difference (ALAD) on Multi-Phasic CT Scan
Authors * Denotes Presenting Author
  1. Melina Hosseiny *; University of California - Los Angeles
  2. Justin Ching; University of California - Los Angeles
  3. Anjalie Gulati; University of California - Los Angeles
  4. Soheil Kooraki; University of California - Los Angeles
  5. Preeti Ahuja; University of California - Los Angeles
  6. Steven Raman; University of California - Los Angeles
Oncocytic lesions such as renal oncocytoma and chromophobe renal cell carcinoma (chRCC) have some overlapping imaging and histological features. This study aimed to investigate the performance of aorta-lesion-attenuation-difference (ALAD), measured on multiphasic multidetector CT scan (MDCT), to distinguish oncocytoma from chRCC.

Materials and Methods:
This IRB-approved, HIPAA-compliant, observational study cohort comprised 111 consecutive patients with pathologically proven oncocytoma (n=74, 40 males) and chRCC (N=37, 27 males). The mean (SD) lesion diameters were 55 (53) and 38 (24) mm in chRCC and oncocytoma subcohorts, respectively. Overall, 76 cases were confirmed on surgery, while biopsy was conclusive in 35 patients (including 24 oncocytoma and 11 chRCC). The largest possible regions of interest (ROIs) were placed over the renal lesion and abdominal aorta on the same MDCT axial slice in all available phases including un-enhanced (UE), corticomedullary (CM), nephrographic (NP) and excretory (EX) to measure the mean Hounsfield Unit (HU). ROIs were devoid of calcification, necrosis and hemorrhage in lesion or atherosclerotic plaque in aorta. The difference between aorta and renal mass HU was calculated in each available phase. SPSS v.18 was used to calculate area-under the curve (AUC) and the optimal ALAD cutoff values for differentiation of chRCC from oncocytoma.

Mean ALAD was significantly higher in chRCC compared to oncocytoma in the CM (P= .04), NP (P<.01) and EX (P<.01) phases. ALAD showed AUC of 0.47 (95% CI: 0.36- 0.59, P= .68), 0.64 (95% CI: 0.51-0.77, P= .03), 0.87 (95% CI: 0.79- 0.95, P<.01) and 0.80 (0.70-0.90, P<.001), in the UE, CM, NP and EX phases, respectively. ALAD cutoff of 19 HU at NP phase had a sensitivity and specificity of 79% and 78%, respectively, for differentiation of chRCC from oncocytoma.

ALAD quantified in the NP phase had the highest accuracy (87%) for differentiation of chRCC from oncocytoma on MDCT. If validated prospectively, ALAD may act as a useful adjunct imaging biomarker to distinguish chRCC from oncocytoma.