Lu-TARGO (177Lu-TARGeted Osteosarcoma Therapy)

This study is testing a new targeted radiation therapy called Lu-TARGO for people with osteosarcoma (a type of bone cancer) that has come back or stopped responding to treatment. The therapy uses a radioactive substance that zeroes in on cancer cells to destroy them. **You may be eligible if...** - You have been diagnosed with osteosarcoma that has relapsed or is no longer responding to treatment - You are at least 12 years old (or 18 for the first group in Phase 1) - You weigh at least 30 kg (about 66 lbs) - Your cancer is measurable on scans or visible on PET imaging - Your cancer has progressed after at least one course of chemotherapy - You are well enough to perform basic daily activities (performance score of 0–2) **You may NOT be eligible if...** - You are currently receiving other anti-cancer treatments - You have HIV, active hepatitis, or other active serious infections - You are pregnant or breastfeeding - You have significant heart problems - You had major surgery within the past 28 days - You have a known allergy to the study drug Talk to your doctor to see if this trial is right for you.