(P 110) DEFINITIVE RADIATION THERAPY IN "OPERABLE" EWING SARCOMA OF THE EXTREMITIES AND PELVIS

Objective: Definitive radiation therapy (RT) has traditionally been reserved for inoperable or metastatic Ewing sarcoma, with limited data on its role in operable disease. However, a subset of patients showing excellent response to neoadjuvant chemotherapy with residual intraosseous disease may represent a favorable group where RT can offer effective local control while preserving function. This study evaluates oncological and functional outcomes in operable Ewing sarcoma treated with definitive RT.

Methods: A retrospective analysis was performed on patients with Ewing sarcoma of the extremities and pelvis treated with definitive RT at our institute between 2013 and 2022. Patients included had operable, non-metastatic disease but received RT alone for local control after demonstrating excellent response to neoadjuvant chemotherapy. Data regarding patient demographics, tumor location, radiation details (dose, timing, technique), and outcomes were collected. Endpoints included local control, systemic recurrence, and survival. Functional outcomes were assessed using the Musculoskeletal Tumor Society (MSTS) score and site-specific functional scales.

Results: contributed to favorable outcomes.Twenty-five patients were included, with 75% involving extremities and the rest pelvis or other skeletal sites. All had operable disease and responded well to chemotherapy. The local control rate with definitive RT was 90%, which compares favorably to published data on RT in Ewing sarcoma. Functional outcomes were encouraging, with high MSTS scores and satisfactory site-specific function. No major treatment-related morbidity affecting limb use was noted. Careful case selection and adherence to RT protocols were pivotal in achieving these outcomes.

Conclusion: Definitive RT provides an effective, function-preserving local control strategy in selected cases of operable Ewing sarcoma with excellent chemotherapy response and residual intraosseous disease. High local control rates and favorable functional outcomes support its use in appropriately chosen patients. Prospective validation of selection criteria, including clinical, radiological, and metabolic response markers, is warranted.