18F-Fluoride PET/CT is highly effective for excluding bone metastases even in patients with equivocal bone scintigraphy

Bone scintigraphy (BS) has been used extensively for many years for the diagnosis of bone metastases despite its low specificity and significant rate of equivocal lesions. F-18-Fluoride PET/CT has been proven to have a high sensitivity and specificity in the detection of malignant bone lesions, but its effectiveness in patients with inconclusive lesions on BS is not well documented. This study evaluated the ability of F-18-fluoride PET/CT to exclude bone metastases in patients with various malignant primary tumours and nonspecific findings on BS. We prospectively studied 42 patients (34-88 years of age, 26 women) with different types of tumour. All patients had BS performed for staging or restaging purposes but with inconclusive findings. All patients underwent F-18-fluoride PET/CT. All abnormalities identified on BS images were visually compared with their appearance on the PET/CT images. All the 96 inconclusive lesions found on BS images of the 42 patients were identified on PET/CT images. F-18-Fluoride PET/CT correctly excluded bone metastases in 23 patients (68 lesions). Of 19 patients (28 lesions) classified by PET/CT as having metastases, 3 (5 lesions) were finally classified as free of bone metastases on follow-up. The sensitivity, specificity, and positive and negative predictive values of F-18-fluoride PET/CT were, respectively, 100 %, 88 %, 84 % and 100 % for the identification of patients with metastases (patient analysis) and 100 %, 82 % and 100 % for the identification of metastatic lesions (lesion analysis). The factors that make BS inconclusive do not affect F-18-fluoride PET/CT which shows a high sensitivity and negative predictive value for excluding bone metastases even in patients with inconclusive conventional BS.