Clinical features and outcomes in patients with extraskeletal ewing sarcoma

BACKGROUND: Ewing sarcoma can arise in either bone or soft tissue. The purpose of this study was to investigate whether patient characteristics, treatment strategies, and outcomes differ between skeletal Ewing sarcoma and extraskeletal Ewing sarcoma (EES). METHODS: Patients <40 years of age with Ewing sarcoma or peripheral primitive neuroectodermal tumor reported to the United States Surveillance, Epidemiology, and End Results Program database from 1973 to 2007 were evaluated based on skeletal (n = 1519) versus extraskeletal (n = 683) site of origin. Patient characteristics were compared using Fisher exact tests. Overall survival was estimated via the Kaplan-Meier method and compared using log-rank tests and Cox proportional hazard models. RESULTS: Patients with EES had a higher mean age (19.5 vs 16.3 years; P < .001) and were less likely to be male (53.4% vs 63.3%; P < .001) or white (84.8% vs 92.5%; P < .001) compared with patients with skeletal tumors. Extraskeletal tumors were more likely to arise in axial locations (72.9% vs 54.2%; P = .001) but were less likely to arise specifically in the pelvis (19.8% vs 26.6%; P < .001). Metastatic status or tumor size did not differ by group. Five-year overall survival was superior for localized EES compared with localized skeletal tumors (69.7% vs 62.6%; P = .02). The hazard ratio for death in patients with localized skeletal tumors compared with localized EES was 2.36 (95% confidence interval, 1.61-3.44) beyond 24 months from initial diagnosis. CONCLUSIONS: Patient characteristics and outcomes differ among patients with EES compared with patients with skeletal Ewing sarcoma. These findings may have important implications for patient care.