• Written informed consent signed before any trial-related procedures are carried out

• Histologically confirmed high-grade sarcoma of bone or soft tissue; the lesion has distant metastasis or is locally advanced and cannot be completely resected at the time of enrollment, or the patient cannot tolerate or refuses surgical resection;

• Have received at least one systemic treatment regimen(s) at the time of enrollment, and have not received prior PARP inhibitor treatment.

• With measurable lesions according to Response Evaluation Criteria in Solid Tumors (RECIST1.1);

• Aged no less than 10 years old and no more than 70 years old;

• For patients ≥16 years old, ECOG score is between 0 and 2 (for patients with amputations, if they can basically take care of themselves and can move freely for more than 50% of their waking hours with the assistance of stretchers, walkers, wheelchairs, etc.) still included);

• For patients under 16 years old, Lansky score is at least 70 or above (for patients with amputations who are unable to participate in active recreational activities due to amputation), if they can participate in most active recreational activities with the assistance of walkers, wheelchairs, etc., they are still eligible included).

• The expected survival time is greater than 24 weeks;

• The majority of the recurrent lesions with an established radiological diagnosis could receive SBRT;

⁃ Major organ functions meet basic safety standards within 7-14 days before treatment.

⁃ Women of childbearing age should agree that they must use contraceptive measures (such as intrauterine devices, birth control pills or condoms) during the study and within 6 months after the end of the study; if in doubt, serum or urine tests within 7 days before study enrollment The pregnancy test is negative and the patient must be non-lactating; the male should agree that contraceptive measures must be used during the study period and within 6 months after the end of the study period;

⁃ If there are recurrent lesions previously treated by surgery, radiofrequency ablation or radiotherapy:

∙ If the image of the metastatic lesion is stable, enrollment is allowed and SBRT is not required for that lesion;

‣ If the metastatic lesion has image progression, if it was previously treated with surgery and SBRT can be performed, enrollment is allowed; if it was previously treated with radiofrequency ablation or radiotherapy, if repeat SBRT can be considered, enrollment is allowed.