Radiomic correlates of molecular and clinicopathological characteristics in clear cell renal cell carcinoma.

Abstract

625 Background: Clear cell renal cell carcinoma (ccRCC) is a highly vascularized tumor and has a heterogeneous molecular profile, but the correlation between its tumor biology and radiomic features have only recently been investigated. As 70% of ccRCCs are detected incidentally at imaging, and tumor phenotypes are only available after surgery, a non-invasive biomarker to predict ccRCC phenotypes and aggressiveness on imaging may be clinically valuable, as low grade lesions may undergo active surveillance. Methods: With IRB approval and HIPAA compliance, our study cohort comprised 92 consecutive patients with 102 ccRCCs (mean age, 62 years (SD ± 14.2) with histopathology and molecular endpoints imaged preoperatively on CT with a four-phase renal protocol [unenhanced (U), corticomedullary (C), nephrographic (N), excretory (E)]. Radiomic data was obtained by contouring the entire ccRCC in each phase to obtain a 3D tumor volume of interest (VOI). The mean enhancement in each phase the and wash-in and wash-out of enhancement was calculated for each ccRCC. Molecular data was obtained through immunohistochemistry of resected ccRCCs to assess carbonic anhydrase-IX (CAIX), microvessel density (MVD), phosphatase and tension homolog (PTEN), and tumor grade (TG). Categorical variables were analyzed with logistic regression and odds ratio (OR) was reported. Continuous variables were analyzed with linear regression and Pearson correlation coefficient (r2) was reported. P-values < .05 were considered significant. Results: Significant radiomic associations included TG and 3D tumor enhancement in the C (OR = 4.72, p = .030), N (OR = 17.71, p < .0001), and E phases (OR = 17.10, p < .0001), and wash-in from U to C (OR = 8.27, p = .004). MVD had a significant positive association with 3D tumor enhancement in the C phase (r2= 0.410, p < .0001), wash-in from U to C (r2= 0.435, p < .0001) and wash-out from the C to N (r2= 0.435, p = .001). There were no significant radiomic correlates with CAIX or PTEN expression. Conclusions: A 3D ccRCC VOI on multiphasic CT had significant correlations with TG and MVD, independent of clinical features, potentially becoming a predictive imaging biomarker of ccRCC aggressiveness and clinical outcome.