177Lu is a radioactive isotope of the element lutetium, commonly used in targeted radionuclide therapy for cancer treatment. It emits beta particles, which can destroy cancer cells while minimizing damage to surrounding healthy tissue. In medicine, 177Lu is often used in conjunction with specific targeting molecules, such as peptides or antibodies, that bind to cancer cells. This targeted approach enhances the effectiveness of the treatment and reduces side effects, making it a promising option for patients with certain types of tumors, including neuroendocrine tumors and prostate cancer.