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%, χ²=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.