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.