Abstract
OBJECTIVE: Spatially fractionated radiation therapy (SFRT) and stereotactic core ablative radiation therapy (SCART), two novel radiotherapy techniques, have demonstrated distinct advantages in the treatment of large-volume tumors. Both approaches allow precise delivery of high-dose radiation to the tumor core while sparing surrounding organs at risk. The objective of this study is to evaluate the efficacy and safety of these two techniques for the treatment of bone metastases accompanied by soft tissue formation. METHOD: Patients with bone metastases accompanied by soft tissue formation will be recruited and assigned to the control or experimental groups. The control group will receive conventional radiotherapy (CRT) with 30 Gy delivered in 10 fractions, while the experimental group will undergo tumor core irradiation using SFRT or SCART with a single dose of 8-12 Gy, followed by whole-bone metastatic lesion radiotherapy with 25-40 Gy delivered in 5 fractions. The primary endpoint is the objective response rate, and secondary endpoints include the pain relief, safety, and local control rates. DISCUSSION: This study evaluates the efficacy and tolerability of using SFRT/SCART for treating bone metastases with soft tissue formation, with the expectation of improving local tumor control and reducing treatment-related toxicities. TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov with the Identifier: NCT06987370 (Registered May 16, 2025).