Search

• Local control for pediatric patients with Ewing Sarcoma treated with proton was comparable to patients who received photon radiation therapy. • Tumor size greater than 8 cm predicted an increased risk of local failure. • Patients with metastatic disease who received radiation therapy to all metastatic sites had favorable survival outcomes. Patients with Ewing Sarcoma (EWS) are treated with multimodality therapy which includes radiation therapy (RT) as an option for local control. We report on the efficacy after proton radiation therapy (PRT) to the primary site for localized and metastatic EWS. Forty-two children with EWS (33 localized, 9 metastatic) treated between 2007 and 2020 were enrolled on 2 prospective registry protocols for pediatric patients undergoing PRT. PRT was delivered by passive scatter (74 %), pencil-beam scanning (12 %) or mixed technique (14 %). Treated sites included the spine (45 %), pelvis/sacrum (26 %), skull/cranium (14 %), extraosseous (10 %), and chest wall (5 %). Median radiation dose was 54 Gy-RBE (range 39.6–55.8 Gy-RBE). Patients with metastatic disease received consolidative RT to metastatic sites (4 at the time of PRT to the primary site, 5 after completion of chemotherapy). Median follow-up time was 47 months after PRT. The 4-year local control (LC), progression-free survival (PFS), and overall survival (OS) rates were 83 %, 71 %, and 86 %, respectively. All local failures (n = 6) were in-field failures. Tumor size ≥ 8 cm predicted for inferior 4-year LC (69 % vs 95 %, p = 0.04). 4-year PFS and OS rates were not statistically different in patients with localized versus metastatic disease (72 % vs 67 %, p = 0.70; 89 % vs 78 %, p = 0.38, respectively). In conclusion, LC for pediatric patients with EWS treated with PRT was comparable to that of historical patients who received photon-RT. Tumor size ≥ 8 cm predicted increased risk of local failure. Patients with metastatic disease, including non-pulmonary only metastases, received radiation therapy to all metastatic sites and had favorable survival outcomes. [ABSTRACT FROM AUTHOR]