18F-FDG PET and PET/CT for detection of pulmonary metastases from musculoskeletal sarcomas

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Abstract
Objective Sarcomas represent a significant therapeutic challenge and their potential for distant pulmonary metastases is well known. [18F]Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) has a role in differentiating sarcomas from benign tumours and assessing the response to therapy in advanced sarcomas. However, PET appears to be less accurate in detection of pulmonary metastases. We were therefore prompted to review our experience with PET and PET/computed tomography (CT) in osseous and soft tissue sarcomas (OSTSs). Methods This is a retrospective study (January 1995 to December 2004) of 106 patients with histological diagnosis of OSTS, who had PET and PET/CT at our institution. The group included 52 men and 54 women, aged 12–92 years (average, 45±20 years). Results For all the patients in the analysis, the sensitivity and specificity were 68.3% (95% CI: 53–80.4) and 98.4% (95% CI: 91.8–99.7) for PET, with 95.1% sensitivity (95% CI: 83.8–98.6) and 92.3% specificity (95% CI: 83.2–96.7) for CT. Pulmonary metastases were seen in 40 patients. CT identified 17 lesions larger than 1.0 cm, while PET identified 13 of them (76.5%). Conclusions Chest CT is more sensitive than PET in detecting pulmonary metastases from OSTS. A significant portion of known pulmonary metastases greater than 1.0 cm on CT, are PET negative. Sub-centimetre CT lesions should not be considered false positive if inactive on PET. A negative PET scan in the presence of suspicious CT findings in the chest cannot reliably exclude pulmonary metastases from OSTS.