ESTRO 2025 - Abstract Book

S1719

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

Material/Methods: This retrospective study included 148 patients (median age 20 years, range 3–69 years) diagnosed with Ewing sarcoma and treated between 2003 and 2021. Patients were stratified by age: childhood (3–11 years, 6.8%), adolescence (12–21 years, 50%), young adult (22–35 years, 23.0%), middle age (36–64 years, 18.9%), and older adult (>65 years, 1.3%). Primary tumors were most commonly located in the pelvis (31.8%) and sacrum (30.4%). At diagnosis, 59.0% of patients had localized disease, while 41.0% presented with metastatic disease. All patients received neoadjuvant chemotherapy followed by either definitive RT (65.5%) or combined surgery + RT (35.5%). Among those undergoing surgery + RT (n = 51), RT was administered preoperatively in 13 patients (25.5%) and postoperatively in 38 patients (74.5%). The median RT dose was 54 Gy (range 30–55.5 Gy) delivered in 1.5 Gy fractions twice daily. Results: At a median follow-up of 57.5 months (range 7–238 months), 65 patients (44.0%) experienced relapse: 11 (17.0%) locally, 15 (23.0%) with local recurrence + distant metastases, and 39 (60.0%) with distant metastases only (median onset 15 months, range 3–198 months). Five-year actuarial rates were: local control (LC) 83.8%, metastasis-free survival (MFS) 65.5%, disease-free survival (DFS) 59.4%, and overall survival (OS) 60.8%. Log-rank tests demonstrated significantly better 5-year MFS and OS in patients without metastases at diagnosis (p < 0.005). Combined treatment with surgery + RT was associated with numerically superior 5-year LC, MFS, DFS, and OS compared to RT alone, though differences were not statistically significant (p = 0.6, p = 0.7, p = 0.3, and p = 0.2, respectively). Lower RT doses (<45 Gy) showed numerically better outcomes for 5-year LC, MFS, DFS, and OS, though again without statistical significance (p = 0.2, p = 0.2, p = 0.5, p = 0.7). Table 1 : actuarial results and univariate analysis.

Conclusion: This single-institution study confirms that Ewing sarcoma patients without metastases at diagnosis and those receiving combined local therapy (surgery + RT) achieve better outcomes compared to those treated with definitive RT alone. The use of log-rank testing underscores the importance of metastasis status at diagnosis in predicting survival outcomes. Further research is required to explore whether higher RT doses can improve local control and survival outcomes.

Keywords: Ewing Sarcoma, Radiotherapy