Image-Guided Biopsies to Identify Mechanisms of Resistance in Patients With Metastatic Castration Resistant Prostate Cancer Treated With 177Lu-PSMA Radioligand Therapy

This study is collecting tumor biopsies from men with advanced prostate cancer who are being treated with a radioactive drug called lutetium-177 PSMA (Lu-PSMA), to understand why some cancers stop responding to this treatment over time. **You may be eligible if...** - You have prostate cancer confirmed by biopsy - You are already eligible for or enrolled in a Lu-PSMA treatment program - Your PET scan shows cancer in lymph nodes or soft tissue that can be safely biopsied - You are willing to undergo an image-guided biopsy **You may NOT be eligible if...** - You have only bone metastases with no soft tissue lesions accessible for biopsy - You have a bleeding disorder or are on blood thinners that cannot be temporarily paused - You are unable to provide informed consent Talk to your doctor to see if this trial is right for you.