did not meet efficacy goals after interim analysis

The purpose of this study is to determine the effectiveness of Estradiol treatment for advanced breast cancer that is hormone receptor negative and Her2/neu negative. The study will also use tumor tissue from your original diagnosis or from a biopsy you may have had for your cancer to look at hormone receptors in the lab. The tissue left over from your previous surgery or a previous biopsy will be used for research tests to check whether a different estrogen receptor (estrogen receptor beta) is seen in the tumor and if that makes estrogen work better.

Inclusion Criteria:

• histologically or cytologically confirmed breast cancer which is metastatic.
• A formalin-fixed paraffin embedded tumor block (preferred) or unstained slides must be available from either a prior biopsy of the primary tumor or a metastatic site. .
• Primary tumor or metastatic biopsy lacking estrogen and progesterone receptor and Her2 negative
• Patients must have measurable disease.
• Eastern Cooperative Oncology Group performance status 0-1.
• Patients with bone metastasis at baseline must agree to treatment with intravenous bisphosphonates
• Subjects may have had 0-4 lines of prior systemic chemotherapy or targeted therapy regimens administered for treatment of their metastatic breast cancer.
• Age >18 years
• Life expectancy of greater than 3 months.
• Patients must have adequate organ and marrow function as defined below:

Exclusion Criteria:

• systemic chemotherapies, targeted therapies or radiotherapy for their cancer within 2 weeks prior to entering the study
• Patients receiving any other investigational agents for breast cancer treatment.
• Patients with known brain metastases are excluded 3.2.4 History of allergic reactions attributed to compounds of similar chemical or biologic composition to estradiol.
• Patients with any condition of the gastrointestinal tract that is expected to result in an inability to take oral medication
• Dysfunctional or post-menopausal vaginal bleeding.
• Uncontrolled hypercalcemia/hypocalcemia
• Prior history of or active thrombophlebitis, cerebral vascular accident, myocardial infarction, deep venous thrombosis or pulmonary embolism.
• History of or active hepatic adenoma.
• Uncontrolled intercurrent illness
• Pregnant women are excluded from this study
• Patients with bone metastasis are excluded if they are unable to receive intravenous bisphosphonate therapy due to the risk for developing hypercalcemia.

Adult women with measurable advanced TNBC.

Adverse event data was collected for 4 years.

Toxicity evaluations including history, examination, and laboratory analysis occurred on day 1 of each cycle.