18-F fluorodeoxyglucose uptake in positron emission tomography as a pathological grade predictor for renal clear cell carcinomas

Objectives: To evaluate the usefulness of Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18-F FDG-PET/CT) in the prediction of Fuhrman pathological grades of renal clear cell carcinoma (cRCC). Methods: This retrospective study was approved by our institutional review board, and written informed consent was waived. Thirty-one patients with pathologically proven cRCC underwent 18-F FDG-PET/CT for tumour staging. Maximum standardized uptake value of cRCC (tumour SUV_max) and mean SUV of the liver and spleen (liver and spleen SUV_mean) were measured by two independent observers. Tumour SUV_max, tumour-to-liver SUV ratio, and tumour-to-spleen SUV ratio were correlated with the pathological grades. Results: Logistic analysis demonstrated that only the tumour-to-liver SUV ratio was a significant parameter for differentiating high-grade (Fuhrman grades 3 and 4) tumours from low-grade (Fuhrman grades 1 and 2) tumours (P = 0.007 and 0.010 for observers 1 and 2, respectively). Sensitivity, specificity, and positive and negative predictive values for detecting tumours of Fuhrman grades 3 and 4 were 64, 100, 100, and 77 %, respectively, for observer 1, and 79, 88, 85, and 83 %, respectively, for observer 2. Conclusions: The tumour-to-liver SUV ratio with 18-F FDG-PET/CT appeared to be a valuable imaging biomarker in the prediction of high-grade cRCC. Key Points: • Tumour SUV_maxwas correlated with the Fuhrman grades. • High-grade tumours have significantly higher SUV_maxthan low-grade tumours. • Tumour-to-liver SUV ratio is useful in the prediction of high-grade cRCC.