For patients with confirmed Ewing sarcoma, pretreatment staging studies should include magnetic resonance imaging (MRI) and/or computed tomography (CT) scan, depending on the primary site. Despite the fact that CT and MRI are both equivalent in terms of staging, use of both imaging modalities may help radiation therapy planning. Whole-body MRI may provide additional information that could potentially alter therapy planning. Additional pretreatment staging studies should include bone scan, CT scan of the chest, and bone marrow aspiration and biopsy. A staging modality under evaluation but not required on current clinical trials is molecular analysis of bone marrow for the presence of fusion transcript. In certain studies, determination of pretreatment tumor volume is an important variable.
Although positron emission tomography using fluorodeoxyglucose (FDG-PET) or FDG-PET/CT are optional staging modalities, they have demonstrated high sensitivity and specificity in Ewing sarcoma and may provide additional information that alters therapy planning. FDG-PET/CT is more accurate than FDG-PET alone in Ewing sarcoma.[3-5]
For Ewing sarcoma, the tumor is defined as localized when, by clinical and imaging techniques, there is no spread beyond the primary site or regional lymph node involvement. Continuous extension into adjacent soft tissue may occur. If there is a question of regional lymph node involvement, an excisional biopsy should be performed.References
- Meyer JS, Nadel HR, Marina N, et al.: Imaging guidelines for children with Ewing sarcoma and osteosarcoma: a report from the Children's Oncology Group Bone Tumor Committee. Pediatr Blood Cancer 51 (2): 163-70, 2008. [PUBMED Abstract]
- Mentzel HJ, Kentouche K, Sauner D, et al.: Comparison of whole-body STIR-MRI and 99mTc-methylene-diphosphonate scintigraphy in children with suspected multifocal bone lesions. Eur Radiol 14 (12): 2297-302, 2004. [PUBMED Abstract]
- Völker T, Denecke T, Steffen I, et al.: Positron emission tomography for staging of pediatric sarcoma patients: results of a prospective multicenter trial. J Clin Oncol 25 (34): 5435-41, 2007. [PUBMED Abstract]
- Gerth HU, Juergens KU, Dirksen U, et al.: Significant benefit of multimodal imaging: PET/CT compared with PET alone in staging and follow-up of patients with Ewing tumors. J Nucl Med 48 (12): 1932-9, 2007. [PUBMED Abstract]
- Treglia G, Salsano M, Stefanelli A, et al.: Diagnostic accuracy of ¹⁸F-FDG-PET and PET/CT in patients with Ewing sarcoma family tumours: a systematic review and a meta-analysis. Skeletal Radiol 41 (3): 249-56, 2012. [PUBMED Abstract]