Efficacy of Stereotactic Body Radiotherapy in Osteosarcoma Bone Metastases.

Osteosarcoma is the most common primary malignancy of bone in children. Stereotactic body radiotherapy (SBRT) is an ablative technique that can overcome radioresistance. The use of SBRT in treating osteosarcoma bone metastases is understudied. Osteosarcoma patients with bony metastases from a single institution were retrospectively reviewed. Treatment response was evaluated per RECIST 1.1 criteria. Adverse effects were evaluated via the Common Terminology Criteria for Adverse Events (CTCAE) grading scale. Thirteen lesions from 9 patients were treated with SBRT. The median time to follow-up was 9.5 months (range 3 to 20.2 mo). Mean pretreatment volume was 48.7 cm 3 . Median delivered dose was 40 Gy in 5 fractions (range 30 Gy in 5 fractions to 48 Gy in 8 fractions). Twelve lesions (92%) showed stable disease (SD). One (8%) lesion showed progressive disease (PD) after 40 Gy in 5 fractions. Local control was 100% at 6 months and 87.5% at 12 months. Pretreatment pain was reported in 78% of patients. Seventy-one percent reported improvement in pain. There were no acute grade ≥3 toxicities observed. SBRT offers promising local control rate in the treatment of osteosarcoma bone metastases with a limited acute side-effect profile. Further studies with a longer follow-up time and larger cohorts are warranted.