Computerized Tomography Measurement of Visceral Adiposity Predicts Plasma Adiponectin Levels and Metastatic Disease in Patients with Clear Cell Renal Cell Carcinoma

Background: Obesity is a risk factor for renal cell carcinoma (RCC). Plasma levels of adiponectin, a hormone secreted solely by adipocytes, inversely correlate with adverse prognostic factors in RCC. Since the volume of the metabolically active visceral adipose tissue (VAT) better reflects obesity associated morbidity than body mass index (BMI), we measured and correlated it to adiponectin levels and disease characteristics in patients with clear cell RCC (ccRCC). Patients and Methods: Visceral and subcutaneous adipose tissues were measured using preoperative CT scans in 25 ccRCC patients who had no previous history of other cancers, diabetes or impaired renal function. Tissue at fat density was separated into subcutaneous and visceral components and the pixels were summed across 3 transverse slices (upper aspect of the L2 vertebral body, the umbilicus and the anterior superior iliac spine) to create a surrogate score of percentage of VAT (visceral fat area/visceral plus subcutaneous fat area). This score was correlated to preoperative fasting plasma adiponectin levels, tumor size, grade, presence of metastasis and BMI by univariate and multivariate linear regression analysis. Results: BMI correlated strongly with total but not visceral fat. Percentage of VAT correlated inversely with plasma adiponectin levels (p < 0.05) and directly with the presence of metastasis (p < 0.05) but not with grade. BMI did not predict either. Conclusion: Visceral obesity is associated with lower levels of plasma adiponectin and also appears to be associated with metastatic disease in ccRCC. CT measurements of percentage of VAT may help in preoperative prognostication of ccRCC patients.