Preoperative Spatially Fractionated Radiation Therapy (SFRT) in Soft Tissue Sarcoma (neoSFRT-SARC)

Inclusion Criteria: * Histologically confirmed soft tissue sarcoma of the extremity or trunk, with tumor size ≥5 cm in greatest dimension (by imaging or clinical examination). * Disease classified as operable or borderline-resectable as determined by the multidisciplinary tumor board. * Age ≥18 years at the time of consent. * Eastern Cooperative Oncology Group (ECOG) performance status 0-2. * Adequate organ function as defined by: Absolute neutrophil count ≥1.5 × 10⁹/L; Platelet count ≥100 × 10⁹/L; Hemoglobin ≥9.0 g/dL; Total bilirubin ≤1.5 × upper limit of normal (ULN) (or ≤3 × ULN in patients with Gilbert's syndrome); AST/ALT ≤2.5 × ULN; Creatinine clearance ≥50 mL/min (by Cockcroft-Gault or measured); * Women of childbearing potential must have a negative serum or urine pregnancy test within 7 days prior to enrollment and agree to use effective contraception during the study treatment period and for at least 3 months after the last study procedure. Men with partners of childbearing potential must agree to use effective contraception during the same period. * Willing and able to provide written informed consent and comply with all study procedures, including scheduled follow-up visits and blood sample collections. Exclusion Criteria: * Prior radiotherapy to the same anatomical site that would result in overlap of radiation fields. * Distant metastases at the time of enrollment (M1 disease). * Pregnancy or breastfeeding. * Active second malignancy requiring systemic therapy within the past 3 years, except for adequately treated basal cell carcinoma, squamous cell carcinoma of the skin, or carcinoma in situ. * Severe, active comorbidities including but not limited to: Uncontrolled infection requiring intravenous antibiotics; Decompensated heart failure (New York Heart Association Class III or IV); Myocardial infarction or unstable angina within 6 months; Severe chronic obstructive pulmonary disease or other conditions that would preclude safe radiotherapy or surgery. * Known hypersensitivity to radiation therapy procedures or inability to undergo required imaging (e.g., MRI contrast allergy not manageable with premedication). * Concurrent participation in another interventional clinical trial with an investigational agent within 30 days prior to enrollment. * Any condition that, in the opinion of the investigator, would compromise patient safety, interfere with study compliance, or preclude successful completion of the study procedures.