Comparison between 18F-NaF PET and PET-CT to detect bone metastases in patients with lung cancer

Objective: To evaluate the effect of 18F-sodium fluoride (18F-NaF) PET-CT in the detection of bone metastases in patients with lung cancer. Methods: Thirty-four patients with newly diagnosed lung cancer were performed with 18F-NaF PET-CT. 18F-NaF PET and 18F-NaF PET-CT were interpreted separately. Lesions were categorized as malignant, benign or inconclusive. A panel of reference methods was used, including MRI (34 patients), 18F-fluorodeoxyglucose PET-CT (4 patients), histopathology (2 patients), or clinical follow-up of at least 6 months (6 patients). Results: In patient-based analysis, 11 of 34 patients had bone metastases. 18F-NaF PET-CT correctly diagnosed all 11 patients with bone metastases, 18F-NaF PET only correctly detected 8 of them. 18F-NaF PET-CT had no false and inconclusive diagnosis. In lesion-based analysis, 118 lesions were assessed which had final diagnosis (47 metastases, 71 benign lesions). 18F-NaF PET-CT was correct in 46 metastatic lesions and 71 benign lesions, but false-negative in lesion. 18F-NaF PET was correct in 27 metastatic lesions and 64 benign lesions, but wrong in 3 lesions (2 benign lesions, 1 metastatic lesions), and equivocal in 24 lesions. Based on the corresponding appearance on low-dose CT, 46 of 47 lesions were categorized metastases (31 presented as sites of increased uptake with corresponding lytic or sclerotic changes, and other 15 metastases show normal or non-specific appearing bone), only 1 sclerotic metastasis was judged benign. All 71 benign lesions have a benign appearance on low-dose CT. In patient- based analysis, categorizing equivocal and malignant interpretation as suggestive for malignancy, the 18F-NaF PET-CT was more specific than 18F-NaF PET (100% vs 78%, χ2=10.78, P<0.05), the sensitivity was 100% for each other. Categorizing equivocal and benign as benignity, the 18F PET-CT was more sensitive than 18F-NaF PET (100% vs 73%, 22=6.41, P<0.001), the specificity between them was not significantly (100% vs 96%, χ2=2.03, P>0.05 ). In lesion-based analysis, the similar results were obtained as patient-based analysis. Conclusion: 18F-NaF PET-CT was both sensitive and specific for detection of bone metastases in patients with newly diagnosed lung cancer. With the diagnosis information of low-dose CT, its ability of differentiation between malignant and benign lesions is improved. (authors)