Neoadjuvant Radiotherapy and Surgery for High-Risk Localized Ewing Sarcoma

Inclusion Criteria: 1. The subject or their legal representative signs the written informed consent prior to enrollment. 2. Age \<= 55 years old. 3. Histologically confirmed Ewing sarcoma, with FET family (including EWSR1 or FUS) gene rearrangement confirmed by FISH or NGS. Clear FET-non ETS fusion cases are excluded. 4. Deemed difficult to achieve a satisfactory surgical margin by 2 or more senior musculoskeletal oncologists. 5. ECOG Performance Status: 0-1. 6. Expected life expectancy \>= 3 months. 7. Women of childbearing potential must have a negative pregnancy test within 1 week prior to enrollment and agree to use contraception; male subjects must agree to use contraception or have undergone surgical sterilization during the study. Exclusion Criteria: 1. No opportunity for surgical resection after neoadjuvant chemotherapy. 2. Extensive metastasis with no indication for local surgical resection. 3. Uncontrolled concurrent medical conditions. 4. Prior radiotherapy to the surgical site during front-line treatment. 5. History of other malignant tumors within the past 5 years. 6. Inability to cooperate with preoperative neoadjuvant radiotherapy (e.g., due to psychiatric factors). 7. Any condition that, in the investigator's judgment, might harm the patient or prevent compliance with study requirements.