Whole-body MR imaging has a higher sensitivity than skeletal scintigraphy for the detection of bone marrow metastases but a lower sensitivity than FDG PET.

Our results demonstrate that SLND in prostate cancer is a reliable procedure for nodal staging.

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.

In 15 osteosarcomas and six Ewing sarcomas, response to preoperative chemotherapy was assessed with magnetic resonance (MR) imaging without and with gadolinium diethylenetriaminepentaacetic acid (DTPA) enhancement and with dynamic Gd-DTPA studies, and the results were compared with the scintigraphic findings. All studies were obtained prior to and following preoperative chemotherapy. Static MR imaging was of little value for assessment of response; reduction in signal intensity within soft-tissue masses on the T2-weighted spin-echo images indicated response with a sufficient degree of accuracy (71%) but low sensitivity, whereas an increase in signal intensity after Gd-DTPA administration indicated zones of viable tissue with low specificity. With three-phase skeletal scintigraphy, the findings in the perfusion and blood-pool phases were of no value, whereas the findings in the osseous phase allowed the prediction of response with an accuracy of 73.7%. Of all techniques employed, dynamic MR imaging had the highest degree of accuracy (85.7%) and was superior to scintigraphy, particularly in patients who were receiving intraarterial chemotherapy.

There seems to be a superiority of spiral CT in the detection of pulmonary metastases from malignant primary bone tumors as compared with FDG-PET. Therefore, at present a negative FDG-PET cannot be recommended to exclude lung metastases. However, as specificity of FDG-PET is high, a positive FDG-PET result can be used to confirm abnormalities seen on thoracic CT scans as metastatic.