Evaluating the Soft Tissue Sarcoma Paradigm for the Local Management of Extraskeletal Ewing Sarcoma

Objectives: We reviewed our experience treating patients with localized extraskeletal Ewing sarcoma (EES) to determine optimal local management strategies for this rare disease. Methods: 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. Results: 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 overall survival was 76%. Twenty-two patients (37%) developed recurrence at a median time of 15 months (IQR, 5–56 months) resulting in 3-year progression-free survival (PFS) of 65%. On univariate analysis, the use of both neoadjuvant and adjuvant chemotherapy was associated with improved 5-year PFS (71% vs. 50%, p =.04) compared with those who received one or the other. Furthermore, 11 patients (18%) developed local recurrences at a median time of 14 months (IQR, 2–19 months), resulting in a 5-year local control (LC) rate of 77%. Use of CMT was not associated with improved LC (83% vs. 72% SMT, p =.41). Also, use of CMT was the only factor associated with poorer disease-specific survival (vs. SMT; hazard ratio, 3.4; p =.047; 95% confidence interval, 1.01–11.4). Conclusion: 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. Implications for Practice: Extraskeletal Ewing sarcoma is a rare chemosensitive sarcoma whose clinical course more closely follows Ewing sarcoma of bone rather than that of other soft tissue sarcomas. Based on this study, combined-modality local therapy did not confer a local control advantage compared with 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.