We reviewed our experience treating patients with localized extraskeletal Ewing sarcoma (EES) to determine optimal local management strategies for this rare disease.

Sixty patients with localized EES treated at our institution between 1994 and 2018 were reviewed. The Kaplan-Meier method was used to estimates disease outcomes.

The median follow-up time was 74 months (interquartile range [IQR], 17-121). Half the patients (n=30) received combined modality local therapy (CMT) with both surgery and radiation therapy (RT), whereas the other half received single modality local therapy (SMT) with either surgery or RT. All patients received chemotherapy. The 5-year OS was 76%. Twenty-two patients (37%) developed recurrence at a median time of 15 months (IQR, 5-56 months) resulting in 3-year PFS 65%. On univariate analysis, the use of both neoadjuvant and adjuvant chemotherapy was associated with improved 5-year PFS (71% vs 50%, p=0.04) compared to those who received one or the other. Furthermore, eleven patients (18%) developed local recurrences at a median time of 14 months (IQR, 2-19 months) resulting in 5-year LC rate of 77%. Use of CMT was not associated with improved LC (83% vs. 72% SMT, P=0.41). Also, use of CMT was the only factor associated with poorer DSS (vs. SMT; HR 3.4, p=0.047, 95% CI 1.01-11.4).

For patients with EES, CMT was not associated with a decreased rate of local relapse. These data suggest that SMT alone may be sufficient for LC in select patients. A multi-institutional collaborative effort should be considered to validate these findings.

Extraskeletal Ewing sarcoma is a rare chemo-sensitive sarcoma whose clinical course more closely follows Ewing's sarcoma of bone rather than that of other soft tissue sarcomas. Based on our study, combined modality local therapy did not confer a local control advantage compared to single modality local therapy. Therefore, single modality local therapy is likely adequate in select patients with favorable disease features, which has the advantage of ensuring prompt administration of systemic therapy. A multi-institutional collaborative effort is warranted to determine which patients may benefit from de-escalated local therapy.