Comparison Of Clinical Features And Outcomes In 3,178 Patients With Extraskeletal Vs Skeletal Ewing Sarcoma

Objective:The clinicopathological characteristics,outcomes and prognostic factors of primary extraskeletal Ewing sarcoma(EES)remained insufficiently explored.We aimed to examine these aspects and compared the same with skeletal Ewing sarcoma(SES).Methods:We identified Ewing sarcoma,peripheral primitive neuroectodermal tumors or Askin tumor patients who were registered in the Surveillance,Epidemiology,and End Results database from 1973 to 2014.Clinicopathological features were assessed by using Fisher's exact tests.Cancer-specific survival(CSS)and overall survival(OS)were estimated by using the Kaplan–Meier method and the Cox proportional hazards model.Prognostic factors were identified by multivariate Cox regression analysis.ResultsThe age of patients with EES was diagnosed to be higher and they were more likely to be female(46.1% vs 36.2%;P<0.001),have tumor <10 cm(49.8% vs 35.4%;P<0.001),have regional node involvement(5.4% vs 1.0%;P<0.001)and receive surgery(69.1% vs 53.8%;P<0.001)compared to patients with skeletal tumors.Metastatic status did not differ by origin.Kaplan–Meier analysis showed that the origin had significant difference in CSS and OS among patients aged 0–19 years and with metastatic stage at presentation.A Cox multivariable model controlling for differences between groups confirmed inferior survival for patients with EES.Age,tumor size,tumor stage and surgery were the most important factors significantly influencing both CSS and OS in the EES and SES patients.Race,year of diagnosis and tumor site were associated with CSS and OS among patients with SES.Conclusion:The general onset age of EES is relatively late,and regional lymph node involvement is common.Most patients receive local surgical treatment,and the histological type is more common with PNET and Askin tumors.The prognosis of EES patients under 20 years old is better than that of SES patients,but the prognosis of EES patients with distant metastasis is worse than that of SES patients.Prognostic factors affecting EES patients include age,tumor size,distant metastasis,and surgical treatment.