Efficacy of Stereotactic Body Radiotherapy in Osteosarcoma Bone Metastases

Summary: Osteosarcoma is the most common primary malignancy of bone in children. Despite intensive treatment with chemotherapy, patients with metastatic disease have a poor prognosis. Stereotactic body radiotherapy (SBRT) is an ablative technique that overcomes radioresistance. However, the use and efficacy of SBRT in treating osteosarcoma metastases is understudied. Osteosarcoma patients with bony metastases from a single institution treated between 2013 and 2024 were retrospectively reviewed. Treatment response was evaluated per RECIST 1.1 criteria with treatment failure defined as progressive disease (PD). Adverse effects of treatment were also evaluated via the Common Terminology Criteria for Adverse Events (CTCAE) grading scale. Twelve lesions from 9 patients were treated with SBRT. Response was evaluated with post-treatment imaging. The median time to follow-up was 5.3 months. The median largest diameter of the lesions was 5.7 cm. The lesions were treated to a median dose of 4000cGy in 5 fractions. Of the 12 evaluated lesions, 75% of patients showed stable disease (SD) and 17% showed partial response (PR) per RECIST 1.1 criteria. 8% of the treated lesions showed PD. Pre-treatment pain was reported in 78% of patients. 71% of these patients reported improvement in pain and 14.5% reported worsening of their pain. 14.5% reported no change in their symptoms. One patient experienced grade 1 radiation dermatitis and one experienced grade 2 pain. Other adverse effects such as severe radiation dermatitis or skin and soft tissue necrosis were not reported. The treatment of osteosarcoma with SBRT shows durable local control in patients with metastatic osteosarcoma. This treatment modality is also shown to be well-tolerated with a limited side effect profile. Additional investigation of treatment of osteosarcoma with SBRT is warranted. Gustavo A. Sosa, MD (Presenting Author) - Vanderbilt University Medical Center; Leo Luo, MD (Co-Author) - Vanderbilt University Medical Center; Scott Borinstein, MD, PhD (Co-Author) - Vanderbilt University Medical Center; Austin Kirschner, MD, PhD (Co-Author) - Vanderbilt University Medical Center; Guozhen Luo, MS (Co-Author) - Vanderbilt University Medical Center