STUDY02001740;22SCH740: Estradiol For ER+ Advanced Breast Cancer (ESTHER)

This study is investigating whether high-dose estrogen (a natural female hormone) can be an effective treatment for postmenopausal women with advanced breast cancer that is hormone receptor-positive (ER+) and has stopped responding to standard hormone-blocking therapies. **You may be eligible if...** - You are a postmenopausal woman with advanced or metastatic ER-positive breast cancer - Your cancer is no longer being treated with curative intent (it has recurred or spread) - You have already received at least one hormone-based treatment (e.g., tamoxifen, aromatase inhibitor, or fulvestrant) **You may NOT be eligible if...** - You have a history of blood clots (deep vein thrombosis or pulmonary embolism) - You have had a stroke, heart attack, or heart failure - You have active and unstable brain metastases - You have recently received another investigational cancer drug (within the past 3 weeks) - You have a prior cancer with a high risk of recurrence Talk to your doctor to see if this trial is right for you.