18F-Fluoride PET/CT for detection of bone metastases in patients with renal cell carcinoma

Objectives To evaluate the role of 18F-Fluoride PET/CT for detection of bone metastasis in patients with renal cell carcinoma (RCC) and compare the same with 18F-FDG PET/CT and 99mTc-MDP bone scintigraphy (BS), when available.

Methods Data of 36 patients (Mean age: 52.5±14.1 years; Male/female: 27/9) with RCC who underwent 18F-Fluoride PET/CT was retrospectively analyzed. PET/CT images were analyzed by two nuclear medicine physicians in consensus, visually and semiquantitatively (SUVmax). Results of 18F-Fluoride PET/CT were compared to 18F-FDG PET/CT (n=16) and BS (n=22). Histopathology/clinical/imaging follow up (minimum-6 months) was used as reference standard.

Results Overall 18F-Fluoride PET/CT showed sensitivity of 100%, specificity of 94.4%, PPV of 94.7%, NPV of 100% and accuracy of 97.2%. It demonstrated total 134 skeletal lesions of which 101 were characterized as metastasis and 33 as benign. Corresponding CT changes were seen for 129/134 lesions. The mean SUVmax of the lesions was 30.3±48.4. 18F-Fluoride PET/CT and 18F-FDG PET/CT showed similar accuracy for visualization of bone metastasis (93.7% vs. 100%; P=0.993). However, 18F-FDG PET/CT also demonstrated extraskeletal metastasis in 6/16 patients. No significant difference was seen between accuracies of BS and 18F-Fluoride PET/CT for visualization of bone metastasis (93.7% vs. 100%; P=0.115), but the former showed more skeletal lesions (91 vs. 44; P<0.0001). In 4/22 patients (18%) with negative BS, 18F-Fluoride PET/CT demonstrated skeletal metastasis.

Conclusions 18F-Fluoride PET/CT shows high diagnostic accuracy for detection of bone metastasis in patients with RCC. It shows comparable results to 18F-FDG PET/CT and detects more skeletal lesions as compared to BS.