This is a single-center, single-arm, prospective observational study to evaluate the long-term local control rate, safety, and efficacy of preoperative neoadjuvant radiotherapy (36-45 Gy) followed by sequential radical surgery and postoperative chemotherapy in patients with high-risk, resectable localized Ewing sarcoma.

Patients diagnosed with high-risk localized Ewing sarcoma will routinely receive standard neoadjuvant chemotherapy. For patients with resectable tumors, preoperative neoadjuvant radiotherapy at a dose of 36-45 Gy will be administered, followed by definitive surgery and subsequent adjuvant chemotherapy. This study does not interfere with standard clinical management and focuses on collecting follow-up data to observe the local recurrence-free survival (LRFS), wound complications, and surgical margin status.

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.

Initial treated ewing sarcoma patients in PKUPH and later would recieve definitivesurgery in PKUPH with complete clinical materials.