Clinical features and outcomes in patients with secondary Ewing sarcoma

Ewing sarcoma (EWS) is rarely diagnosed as a second malignancy. We sought to describe a cohort of patients with secondary EWS and investigate if patient characteristics and survival differ between patients with secondary and primary EWS.

Patients with EWS or peripheral primitive neuroectodermal tumor (PNET) reported to the Surveillance, Epidemiology, and End Results Program (SEER) database from 1973 to 2008 were evaluated based on primary or secondary tumor sequence. Overall survival was estimated by Kaplan-Meier methods and evaluated using the log-rank test. Competing risk analysis was used to describe risk of death due to malignancy rather than other causes.

Fifty-eight cases of secondary EWS were reported, accounting for 2.1% of all EWS cases. The median latency from primary malignancy to secondary EWS was 64 months (range 1-282 months). 12.1% of patients with secondary EWS received radiation to the site of secondary tumor during therapy for their primary malignancy. Patients with secondary EWS were more likely to have axial tumors (77.4% vs. 62.5%; P = 0.03) and smaller tumors (75.0% vs. 48.2% <8 cm; P = 0.001). Five-year overall survival from diagnosis was inferior for patients with secondary compared to primary EWS (34.3% vs. 52.2%; P = 0.002). However, patients with secondary tumors were less likely than those with primary EWS to die from their malignancy [hazard ratio 0.44; 95% confidence interval (CI) 0.23-0.85].

Secondary EWS accounts for a minority of cases of EWS. Tumor size and site and patient survival differ among patients with primary and secondary EWS.