Prognostic Factors and Clinical Outcomes in Extraskeletal Ewing Sarcoma: A Cohort Study.

Background: Extraskeletal Ewing sarcoma (ESE) is a lesser-known, rarer counterpart of Ewing sarcoma of bone. This single-center study sought to evaluate the prognosticators and outcomes following multimodality therapy in patients with ESE.

Methods: Forty-seven patients with ESE, treated between 2013 and 2018 with a standardized protocol and multimodality therapy using established doxorubicin-based regimens, were followed-up to assess outcomes.

Results: Median age at diagnosis was 20 (range 7-56) years, and 57.4% were male. Median tumor size was 7 (range 2-21) cm. The symptom-duration ranged from 1 to 8 (median 4) months. Tumor-site was trunkal in 61.7%, extremity in 23.4%, and head and neck 14.9%. Of the 35 patients with nonmetastatic disease at presentation, 13 underwent upfront surgery. The rest received chemotherapy followed by local treatment, which was surgical in 15 and radiotherapy in 5. At median follow-up of 24 (range 5-98) months, 55.3% patients had experienced events, and 29.8% had died of progressive disease. Three-year event-free survival was 41.1%, and overall survival was 53%. On univariate analysis, trunkal location, upfront surgery, and positive surgical margins were associated with inferior EFS. Trunkal tumors and upfront surgery were also associated with poorer OS. On multivariate analysis, trunkal location and margin-positive resections retained statistical significance for adverse EFS.

Conclusions: Unless clearly resectable upfront, ESE should be downstaged with chemotherapy before local treatment. A margin-negative resection should be the objective when performing surgery. Definitive radiotherapy is an alternative in tumors not amenable for complete excision or when anticipated postoperative morbidity precludes radical surgery.