Imaging of pediatric bone tumors: Osteosarcoma and Ewing sarcoma

Key Points: □ The initial imaging test for suspected bone tumors is radiography. Some lesions can be definitely determined to be benign (nonaggressive) based on radiography alone, but in other cases, surgical excision or biopsy will be necessary for diagnosis (limited evidence). □ Local staging of bone sarcomas is best performed with contrast-enhanced MRI. Precontrast T1-weighted images best depict intraosseous extent, while postcontrast images evaluate soft tissue component and joint invasion (moderate to limited evidence). □ Prognosis: Large tumor size is a poor prognostic factor for both OS and ES and correlates with the presence of distant metastases (moderate evidence). Intensity of uptake on PET may correlate with prognosis/survival (limited evidence). □ Skip metastases in the bone are best detected on T1-weighted MR images (moderate evidence). □ Staging: Chest CT is essential to detect lung metastases. Detection of bone metastases is best performed with scintigraphy for OS and with FDG-PET for ES (moderate to limited evidence). □ While reduction of tumor size correlates with response in Ewing's sarcoma, this is not true for OS. The role of imaging in assessing response to chemotherapy remains limited (moderate evidence). □ Optimal posttreatment imaging surveillance protocols are not well defined. The recommendations from the children's oncology group have been summarized.