RecruitingPhase 2Combination productPulmonary Resectable Osteosarcoma Treated by Metastasectomy and Pre-operative Immunotherapy and Stereotactic Body Radiotherapy (PROMIS): a Prospective Clinical TrialThe aim of this study is to evaluate the efficacy and safety of pre-operative concurrent Stereotactic Body Radiotherapy (SBRT) and and programmed cell death protein-1 (PD-1) blockade immunotherapy followed by surgical metastasectomy for resectable metastatic osteosarcoma.