Added value of 18F-FDG PET-CT in staging of Ewing sarcoma in children and young adults

Ewing sarcoma (ES) is currently staged using Radiography, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI) and skeletal scintigraphy (bone scan). 18 F- fluorodeoxyglucose Positron Emission Tomography ( 18 F-FDG PET-CT) is increasingly used for staging and follow-up, but its role is still under evaluation. To evaluate the added information from 18 F-FDG PET-CT studies compared to conventional imaging and to estimate radiation doses received from radiological and nuclear medicine imaging during staging of Ewing sarcoma. Sixty-one patients under the age of 30 years (mean 16, range 5–26) were diagnosed with Ewing sarcoma in Norway during the period 2005–2012. Nineteen patients met the inclusion criteria for this population-based study: pre therapeutic 18 F-FDG PET-CT and a minimum follow-up of 12 months. Imaging reports, medical records and pathology reports were collected and compared for all patients. Biopsy histology, supplementary imaging and long-term follow-up (median 27 months) were taken as composite gold standard. 18 F-FDG PET-CT detected more lesions than conventional imaging in four patients (21%) but this did not change planned treatment as they all had extensive metastatic disease. The 18 F-FDG PET-CT study was false negative in one patient and showed false positive lesions in three patients (16%). The estimated mean (range) effective total radiation dose was from CT: 7 mSv (2–16), skeletal scintigraphy: 3 mSv (0–5) and 18 F-FDG PET-CT: 5 mSv (4–6). 18 F-FDG PET-CT is useful for staging of Ewing sarcoma and increase detection of metastases. False positive lesions are quite common, emphasizing the need for supplementary imaging or biopsy of suspected FDG positive metastases.