Radiation therapy dose escalation achieves high rates of local control with tolerable toxicity profile in pediatric and young adult patients with Ewing sarcoma

Background: Local control for patients with Ewing sarcoma (EWS) who present with large tumors are suboptimal when treated with standard radiation therapy (RT) doses of 54-55.8 Gy. The purpose of this study is to determine local control and toxicity of dose-escalated RT for tumors ≥8 cm (greatest diameter at diagnosis) in pediatric and young adult patients with EWS.

Methods: Eligible patients ≤30 years old with newly diagnosed EWS ≥8 cm treated with definitive conformal or intensity modulated photon, or proton radiation therapy techniques were included. All patients in the study received dose-escalated RT doses. Outcomes included overall survival (OS), event-free survival (EFS), local failure rates, and toxicity.

Results: Thirty-two patients were included, 20 patients presented with metastatic disease and 12 patients with localized disease. The median RT dose was 64.8 Gy (range, 59.4-69.4 Gy) with variability of doses to protect normal surrounding tissues. All patients received systemic chemotherapy. The 5-year OS and EFS for the cohort was 64.2% and 42%, respectively. The 5-year cumulative incidence of local failure was 6.6%. There were two combined local and distant failures with no isolated local failures. Twenty-nine patients experienced short term toxicity, 90% of those being radiation dermatitis. Twenty-seven patients experienced long-term toxicity, with only one experiencing grade 4 toxicity, a secondary malignancy after therapy.

Conclusion: This study demonstrates that definitive RT for pediatric and young adult patients with EWS ≥8 cm provides high rates of local control, while maintaining a tolerable toxicity profile.