• 1. Patients aged 18 to 75 years (calculated as of the date of signing the informed consent), regardless of gender.

• 2\. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2. 3. Histologically confirmed advanced or metastatic Ewing sarcoma, with at least one measurable lesion that has not been treated locally (according to RECIST v1.1, this measurable lesion must have a maximum diameter of ≥ 10 mm on spiral CT scans or a short diameter of ≥ 15 mm for enlarged lymph nodes).

• 4\. The primary tumor or locally recurrent tumor cannot be completely resected through surgery or other local treatments (e.g., stereotactic radiosurgery, argon-helium knife, ultrasound-guided focused ultrasound, etc.); first-line chemotherapy (VAC/IE) has failed, leading to distant metastasis, and the metastatic tumors cannot be completely resected through surgery or other local treatments; or the patient refuses surgery or other local treatments.

• 5\. Expected survival of ≥ 12 weeks. 6. Basic normal function of major organs, with severe abnormalities in blood, heart, lung, liver, kidney, bone marrow functions, or immune deficiency diseases meeting protocol requirements:

⁃ Complete Blood Count (CBC): (No blood transfusion, use of Granulocyte-Colony Stimulating Factor \[G-CSF\], or corrective therapy within 14 days prior to screening)

⁃ \- Hemoglobin ≥ 90 g/L;

‣ Neutrophil count ≥ 1.5 × 10\^9/L;

‣ Platelet count ≥ 75 × 10\^9/L;

⁃ Biochemical Tests: (No albumin infusion within 14 days)

∙ Albumin ≥ 29 g/L;

‣ Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) ≤ 2.5 times the upper limit of normal (ULN);

‣ Total bilirubin (TBIL) ≤ 1.5 times ULN;

‣ Creatinine (Cr) ≤ 1.5 times ULN or Cr clearance \> 50 mL/min (Cockcroft-Gault formula):

‣ Male: Cr clearance = ((140 - age) × weight) / (72 × blood Cr)

‣ Female: Cr clearance = ((140 - age) × weight) / (72 × blood Cr) × 0.85

‣ Weight in kg; blood Cr in mg/mL;

‣ Urinary protein \< 2+ (if urinary protein ≥ 2+, a 24-hour urine protein quantification can be performed, with \< 1.0 g in 24 hours allowing for inclusion);

⁃ Coagulation Function: Activated partial thromboplastin time (APTT) and International Normalized Ratio (INR) ≤ 1.5 × ULN (patients on stable doses of anticoagulants like low molecular weight heparin or warfarin, with INR within the expected therapeutic range, can be screened);

⁃ Thyroid Function: Thyroid-Stimulating Hormone (TSH) ≤ ULN; if abnormal, T3 and T4 levels should be evaluated, with normal levels allowing for inclusion;

⁃ Echocardiogram: Left ventricular ejection fraction (LVEF) ≥ 60%. 7. Non-surgically sterile or premenopausal female patients must use a medically approved contraceptive method (such as an intrauterine device, contraceptive pills, or condoms) during the study treatment period and for 6 months after the end of study treatment; non-surgically sterile premenopausal females must have a negative serum or urine HCG test within 7 days prior to study enrollment and must not be breastfeeding; male patients with female partners of childbearing potential should use effective contraception during the study and for 6 months after the last dose of fluzoparib, liposomal irinotecan, or temozolomide.

⁃ 8\. Understanding the study procedures and methods, voluntarily participating in this trial, and signing the informed consent form in writing, with a full understanding of the trial content, process, and potential adverse reactions.