Correlation of tumor enhancement and imaging features on multiphasic multidetector CT with microvessel density as a step toward a minimally invasive method to predict Fuhrman nuclear grade in patients with clear cell renal cell carcinoma.

e16049 Background: Clear cell renal cell carcinoma (ccRCC) is the most common tumor of the kidney. Up to 70% are incidentally detected on multiphasic CT. The prognosis for patients with ccRCC is related to Fuhrman grade (FG) and is diagnosed by biopsy or excision. There is a great need for a non-invasive method to assess tumor grade which may help inform clinical decision-making. The purpose of our study is to determine if contrast enhancement on CT predicts FG and microvessel density (MVD) of ccRCC lesions and to assess which combination of quantitative and qualitative radiological features and clinical features predict high FG ccRCC lesions. Methods: With IRB approval for this HIPAA-compliant retrospective study, our pathology and imaging databases were queried to obtain a cohort of ccRCC with a preoperative multiphasic (unenhanced (U), corticomedullary (C), nephrographic (N), and excretory (E)) CT scan. Tumors were stained with CD4 to quantify % MVD. Spearman’s rank correlation was calculated to test the strength of the association between CT enhancement, %MVD and FG. Stepwise logistic regression analysis was performed to determine the quantitative and/or qualitative feature with the highest performance in predicting high FG tumor. The multivariate logistic regression analysis was evaluated using ROC curves and AUCs. Results: Our cohort had 127 patients with 89 low-grade tumors and 43 high-grade tumors. The %wash-in of enhancement from the U to the C phase showed a significant correlation with %MVD of the tumor (R 2 = 0.181,p < . 001) as did enhancement of the tumor in the early C phase with %MVD (R 2 = 0.159,p < . 001). There was a significant inverse correlation with %MVD and FG (R 2 = 0.137,p < . 001). T-stage, tumor size, %MVD and presence of renal vein invasion were determined to be significant independent predictors of high grade lesions with an AUC of .838 (95% CI .748-.927). Conclusions: Lower grade ccRCC tumors have a higher MVD. Therefore, contrast material washes in at a faster rate from the UN to the CM phase, enabling low grade to be discriminated from high-grade tumors on CT.