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OBJECTIVE: Extraskeletal Ewing sarcoma (EES) is a variant of Ewing sarcoma that originates from soft tissues rather than bones. Our study aims to characterize the differences between EES and skeletal ES (SES) in the pediatric population. METHODS: We conducted a retrospective review of children ≤ 18 years with ES recorded in the National Cancer Data Base (NCDB) from 2004 to 2022. Kaplan-Meier curves and Cox proportional hazards regression analysis were used to identify risk factors associated with survival. RESULTS: Among 7446 identified patients, 1016 (20.9%) had EES and 6430 (79.1%) had SES. EES patients were older (median 14 vs. 13 years, p = 0.007), more often female (46.9% vs. 41.2%, p = 0.0009), and had smaller tumors (7.5 vs. 8.0 cm, p = 0.003). Tumor distribution differed significantly, with EES was most frequent in the thorax (49.8%) and head and neck (11.8%), while SES more common in the lower limbs (30.2%) and pelvis (25.3%) (p < 0.0001). EES patients were more likely to receive surgery alone (4.2% vs. 1.8%) or a combination of surgery, chemotherapy, and radiation (25.9% vs. 20.7%) but less likely to receive chemotherapy and radiation without surgery (19.4% vs. 29.3%, p < 0.05). Five-year overall survival was similar between SES (72.2%) and EES (73.7%) (p = 0.70). Multivariable analysis confirmed EES was not an independent predictor of survival (aHR 0.94; 95% CI 0.81-1.10). Factors independently associated with mortality were older age, metastasis at diagnosis, and positive surgical margins. CONCLUSIONS: Demographic, treatment characteristics, and prognostic factors differ between pediatric patients with SES and EES. However, survival is similar between the two groups.
Chidiac et al. (Thu,) studied this question.