A prospective diagnostic accuracy study of F-18 fluorodeoxyglucose-positron emission tomography/computed tomography in the evaluation of indeterminate renal masses.

Objective: We evaluated the efficacy of fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET)/computerized tomography (CT; F-18 FDG-PET/CT) in the detection of renal cell carcinoma (RCC) in patients with indeterminate renal masses.

Methods: Between December 2008 and June 2010, 18 patients with suspicious primary renal masses detected by conventional imaging underwent FDG PET/CT imaging. All patients underwent nephrectomy or surgical resection of the renal mass and the final diagnoses were based on histopathology.

Results: Fifteen patients had RCC (14 clear-cell RCC, one papillary RCC). Three renal tumors were benign, corresponding to two renal cortical cysts and one oncocytoma. FDG PET/CT accurately detected seven malignant lesions and yielded false-negative results in eight patients. FDG PET/CT was true negative in two patients with a renal cortical cyst and false positive in a patient with oncocytoma. PET showed a sensitivity of 46.6%, specificity of 66.6%, and accuracy of 50% for primary RCC tumors. The median size of visualized tumors was greater than the median size of nonvisualized tumors, and the average Fuhrman grade of the patients with FDG-positive malignant lesions were higher than that of the patients with FDG-negative lesions. In malignant tumors, the change between early and delayed imaging for average standardized uptake values and maximum SUVs were not statistically significant.

Conclusions: FDG PET/CT is not a reliable modality in the diagnosis of RCC with its low sensitivity, but it is effective in the detection of distant metastases and can be used as a complementary tool when conventional imaging studies yield equivocal results.