Diagnostic Accuracy of 18F-FDG PET/CT in the Staging and Assessment of Response to Chemotherapy in Children with Ewing Sarcoma

Introduction: The purpose of this study was to evaluate the potential role of fluorine-18 fluorodeoxyglucose (18F-FDG) positron-emission tomography/computed tomography (PET-CT) in the staging and assessment of chemotherapy response in Ewing sarcoma. Materials and Methods: For 13 patients with Ewing sarcoma, whole-body FDG PET-CT was assessed for site of primary disease, disease extent, and response to therapy. Chest CT, localized magnetic resonance imaging or CT of primary site, and bone scintigrams were evaluated for imaging features of the primary lesion and presence or absence of metastatic disease. Response to therapy was also assessed. Descriptive statistics are reported. Results: Nine patients (69%) presented metastatic disease. All metastatic lung lesions were detected by spiral CT, but some failed to be detected using FDG PET-CT. As regards bone lesions, both FDG PET-CT and bone scans were able to identify bone metastasis, but FDG PET-CT identified more lesions than bone scans. All PET-CT scans at the end of the neoadjuvant chemotherapy showed a decreased FDG uptake. Conclusions: FDG PET-CT seems to be superior to bone scan in the detection of bone metastasis in all districts except skull bones. For pulmonary metastasis smaller than 7 mm, FDG PET-CT is less sensitive than CT. FDG PET-CT may have an important role in initial staging of Ewing sarcoma and subsequent evaluation of response to therapy.