A Study of Radiation Dosimetry, Safety, and Tolerability of Extended Lutetium (177Lu) Vipivotide Tetraxetan Treatment in Chemo-naïve Adults With Metastatic Castration-resistant Prostate Cancer: RADIOpharmaceutical DOSimetry Evaluation (RADIODOSE) Study

This study is testing a radioactive drug called lutetium-177 (Lu-177 PSMA) in men with prostate cancer that has spread and stopped responding to hormone therapy — but who have not yet received chemotherapy. Researchers want to understand how the drug travels through the body and what dose is safe for longer-term use. **You may be eligible if...** - You are 18 or older and have prostate cancer confirmed by biopsy - Your cancer has spread to at least one area on a scan - Your cancer shows a specific protein called PSMA on a special PET scan - Your testosterone is at castrate levels (very low) from medication or surgery - Your cancer progressed after one type of hormone-blocking pill (like enzalutamide or abiraterone) - Your kidneys are working reasonably well **You may NOT be eligible if...** - You have previously received chemotherapy for prostate cancer - You have had any prior radioligand therapy or certain other radioactive treatments - You have had a heart attack or serious heart condition in the past 6 months - You have another active cancer affecting your life expectancy - You have serious kidney disease Talk to your doctor to see if this trial is right for you.