Atezolizumab in Combination With Stereotactic Body Radiation Therapy (SBRT) and Surgery for Relapsed Osteosarcoma

Removal of all lung nodules, including the radiated nodule, per the standard of care for osteosarcoma patients with lung metastasis.

Dose level 1: 8 Gy\* 3 (Total 24 Gy) Dose level 2: 18 Gy\* 3 (Total 54 Gy)

For subjects \<18 years of age at the time of enrollment, Atezolizumab will be administered IV on Day 1 of each 21-day cycle at a dose of 15 mg/kg (maximum dose of 1200 mg). Subjects ≥ 18 years old will receive a flat dose of 1200 mg IV on Day 1 of each 21-day cycle