Prognostic and therapeutic factors influencing the clinical outcome of metastatic Ewing sarcoma family of tumors: A retrospective report from the Japan Ewing Sarcoma Study Group

[Background] The prognosis of patients with metastatic Ewing sarcoma family of tumors (ESFT) remains poor. [Procedure] We retrospectively analyzed 57 patients diagnosed with metastatic ESFT between 2000 and 2018 to identify prognostic and therapeutic factors affecting the clinical outcome. [Results] The 3-year overall survival (OS) rate of the entire cohort was 46.8% (95% confidence interval [CI], 33.0-59.4%). Treatment-related death was not observed. Multivariate analysis identified stem cell transplantation (SCT), response to first-line chemotherapy, and bone metastasis as independent risk factors for OS. Objective response rate to first-line chemotherapy was 65.1% in the 43 evaluable patients. There was no significant difference in the response to different types of first-line chemotherapy. Among patients with lung metastasis alone, the 3-year OS rate was higher in 13 patients who received local treatment than in four who did not, although the difference was not significant. [Conclusions] One possible reason for the high OS rates was the absence of treatment-related mortality even in patients receiving SCT, which could be attributed to advances in the management of post-SCT complications. Novel first-line chemotherapy strategies need to be established to improve the disease status prior to SCT in a higher proportion of patients