A Phase 1 Study of 68Ga-R11228 and 177Lu-R11228 in Breast Cancer

This Phase 1 study is testing a new targeted imaging and treatment agent for hormone receptor-positive (HR+), HER2-negative breast cancer that has spread (metastatic). The drug uses two different radioisotopes: 68Ga-R11228 for PET scanning to detect cancer, and 177Lu-R11228 for delivering targeted radiation therapy directly to cancer cells. **You may be eligible if...** - You are 18 or older (male or non-pregnant female) with confirmed HR+/HER2- breast cancer that has returned locally or spread to other parts of the body - For the imaging part (Part A): you have at least one measurable lesion - For the treatment part (Part B): your cancer has stopped responding to standard hormone therapy and CDK4/6 inhibitors, and you have received prior chemotherapy for metastatic disease **You may NOT be eligible if...** - You are pregnant or breastfeeding - You have significant organ dysfunction (heart, liver, kidneys) - Your cancer is HER2-positive - You have active brain metastases Talk to your doctor to see if this trial is right for you.