FDG-PET for detection of osseous metastases from malignant primary bone tumours: comparison with bone scintigraphy

The purpose of this study was to compare positron emission tomography using fluorine-18 fluorodeoxyglucose (FDG-PET) and technetium-99m methylene diph osphonate (MDP) bone scintigraphy in the detection of osseous metastases fr om malignant primary osseous rumours. In 70 patients with histologically pr oven malignant primary bone rumours (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 ref erence methods for both imaging modalities were histopathological analysis, morphological imaging [additional conventional radiography, computed tomog raphy (CT) or magnetic resonance imaging (MRI)] and/or clinical follow-up o ver 6-64 months (median 20 months). In 21 examinations (18%) reference meth ods revealed 54 osseous metastases (49 from Ewing's sarcomas, five from ost eosarcomas). FDG-PET had a sensitivity of 0.90, a specificity of 0.96 and a n 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, respectivel y. Analysing only Ewing's sarcoma patients, the sensitivity, specificity an d 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 osse ous 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.