The goal of this observational study is to determine the impact of 177Lutetium-Prostate Specific Membrane Antigen (PSMA) Radioligand Therapy (177Lu-PSMA-RLT) on kidney function over time. The main question it aims to answer is: What is the absolute decline in estimated glomerular filtration rate (eGFR) in patients undergoing 177Lu-PSMA-RLT after 12 and 24 months? Patients treated with 177Lu-PSMA-RLT will have their kidney function monitored before, during, and after therapy using routine markers like creatinine and cystatin C. Additional biomarkers and urine proteomics will be collected to identify early detection markers and risk factors for chronic kidney disease (CKD). Follow-up examinations will be conducted at regular intervals up to 5 years. The study also aims to correlate clinical risk factors and patient-reported outcomes with kidney insufficiency to assess the impact of therapy and identify vulnerable patient groups.