The purpose of this study was to compare positron emission tomography using
fluorine-18 fluorodeoxyglucose (FDG-PET) and technetium-99m
methylene diphosphonate (MDP) bone scintigraphy in the detection of osseous
metastases from malignant primary osseous tumours. In 70 patients with histologically proven malignant primary bone tumours (32
osteosarcomas, 38 Ewing's
sarcomas), 118 FDG-PET examinations were evaluated. FDG-PET scans were analysed with regard to osseous
metastases in comparison with bone scintigraphy. The reference methods for both imaging modalities were histopathological analysis, morphological imaging [additional conventional radiography, computed tomography (CT) or magnetic resonance imaging (MRI)] and/or clinical follow-up over 6-64 months (median 20 months). In 21 examinations (18%) reference methods revealed 54 osseous
metastases (49 from Ewing's
sarcomas, five from
osteosarcomas). FDG-PET had a sensitivity of 0.90, a specificity of 0.96 and an accuracy of 0.95 on an examination-based analysis. Comparable values for bone scintigraphy were 0.71, 0.92 and 0.88. On a lesion-based analysis the sensitivity of FDG-PET and bone scintigraphy was 0.80 and 0.72, respectively. Analysing only
Ewing's sarcoma patients, the sensitivity, specificity and accuracy of FDG-PET and bone scan were 1.00, 0.96 and 0.97 and 0.68, 0.87 and 0.82, respectively (examination-based analysis). None of the five osseous
metastases from
osteosarcoma were detected by FDG-PET, but all of them were true-positive using bone scintigraphy. In conclusion, the sensitivity, specificity and accuracy of FDG-PET in the detection of osseous
metastases from Ewing's
sarcomas are superior to those of bone scintigraphy. However, in the detection of osseous
metastases from
osteosarcoma, FDG-PET seems to be less sensitive than bone scintigraphy.