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

PURPOSE

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.

MATERIALS AND 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.

CONCLUSION

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.