The adaptive trial design of this advanced Phase II study incorporates (i) a dosing schedule based on the patient's estimated tumor burden and not on standard dosing per kilogram body weight or body surface area, and (2) a tumor response evaluation process that is unique to the manner in which osteosarcoma responds favorably to therapy, i.e., with necrosis and increasing calcification in metastatic tumors and decreased glucose utilization using PET-CT imaging studies.