Outcomes of Pediatric Patients with metastatic Ewing sarcoma treated with interval compression

Background: Interval compression (IC), defined as 2 week-long cycles of alternating vincristine/doxorubicin/cyclophosphamide and ifosfamide/etoposide, improves survival for localized Ewing sarcoma. The outcomes of patients with metastatic disease treated with IC are uncertain. Methods: We retrospectively reviewed the charts of pediatric patients with metastatic Ewing sarcoma treated with IC at our center between January-2013 and March-2020. We calculated event-free survival and overall survival and used log rank tests for univariate comparisons. Results: We identified 34 patients aged 2.7–17.1 years (median,11.6 years). Twenty-six patients (76%) had pulmonary metastases, and 14 (41%) had extra-pulmonary metastases in the bone (n = 11), lymph nodes (n = 2), and intraspinal tissue (n = 1). All patients received local control therapy: surgery only (n = 7, 21%), radiotherapy only (n = 18, 53%), or both (n = 9, 26%). The estimated 3-year OS and EFS were 62%±9% and 39%±9%, respectively. Patients with pulmonary only metastasis had a 3-year OS of 88%±8% in comparison to those with extra-pulmonary metastasis of 27%±13% (P=0.0074). Survival did not differ according to age group (> vs < 12 years), metastasis site, or primary tumor site, but 3-year event-free survival significantly differed according to local control therapy (surgery only, 83% ± 15%; combined surgery and radiation, 30% ± 18%; radiation only, 15% ± 10%; P = .048). Conclusion: IC yielded similar outcomes for patients with metastatic Ewing sarcoma to that reported in the literature using other regimens. We suggest including this approach to other blocks of therapy