Extraosseous Ewing Sarcoma in Children: A Systematic Review and Meta-Analysis of Clinicodemographic Characteristics.

Background: We conducted this systematic review to provide comprehensive evidence on the prevalence, clinical features and outcomes of young extraosseous Ewing sarcoma (EES) cases. Methods: PubMed, Scopus, Web of Science, and Google Scholar were searched for articles reporting the occurrence of EES among children and adolescents (<21 years). The primary outcome included the rate of occurrence of EES among children and adolescents, while the secondary outcomes included the descriptive analyses of the demographic characteristics, tumor characteristics, and clinical outcomes of the affected cases. The data are reported as the effect size (ES) and its corresponding 95% confidence interval (CI). Results: A total of 29 studies were included. Twenty-four reported instances of childhood disease among all the EES cases [ES = 30%; 95%CI: 29-31%], while five studies reported extraosseous cases among the pediatric EES cases [ES = 22%; 95%CI: 13-31%]. The thorax is the most common location of childhood EES [33%; 95%CI: 20-46%] followed by the extremities [31%; 95%CI: 22-40%]. Concurrent chemotherapy and radiotherapy [57%; 95%CI: 25-84%] was the most commonly implemented management protocol in the pediatric EES cases. The rate of no evidence of disease and 5-year overall survival was 69% for both outcomes. Mortality occurred in 29% of cases, while recurrence and secondary metastasis occurred in 35% and 16% of cases, respectively. Conclusions: Our findings provide insight into the clinical features and outcomes of EES among children and adolescents.