FDG-PET for detection of pulmonary metastases from malignant primary bone tumors: Comparison with spiral CT

Background: The purpose was the comparison of positron emission tomography using F-18-fluorodeoxy-glucose (FDG-PET) and spiral thoracic CT to detect p ulmonary metastases from malignant primary osseous tumors. Patients and methods: In 71 patients with histologically confirmed malignan t primary bone tumors (32 osteosarcomas, 39 Ewing's sarcomas) 111 FDG-PET e xaminations were evaluated with regard to pulmonary/pleural metastases in c omparison with spiral thoracic CT. Reference methods were the clinical foll ow-ups for 6-64 months (median 20 months) or a histopathologic analysis. Results: In 16 patients (23%) reference methods revealed a pulmonary/pleura l metastatic disease. FDG-PET had a sensitivity of 0.50, a specificity of 0 .98, and an accuracy of 0.87 on a patient based analysis. Comparable values for spiral CT were 0.75, 1.00, and 0.94. It was shown that no patient who had a true positive FDG-PET had a false negative CT scan, nor was a pulmona ry metastases detected earlier by FDG-PET than by spiral CT. Conclusions: 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 pos itive FDG-PET result can be used to confirm abnormalities seen on thoracic CT scans as metastatic.