The purpose of this study is to test the effectiveness and safety of fulvestrant in premenopausal women with advanced breast cancer.

Patients will receive an injection of fulvestrant on first day of treatment and then again 2 weeks later and again 2 weeks after that. Then patients will receive injections every 4 weeks.

Routine blood tests will be performed each time an injection is given.

Patients will be required to complete a hot flash diary, recording the number and severity of hot flashes they experience on a daily basis.

After every 12 weeks of treatment, patients' disease will be assessed by x-rays or scans. If there is no disease progression, the patient will continue to receive injections every 4 weeks with reassessment every 8 weeks.

Patients will continue to receive treatment as long as there is no disease progression or serious side effects.

Inclusion Criteria:

• Histologically or cytologically confirmed invasive breast cancer, with stage IV disease.
• Tumors must be positive for estrogen receptors, progesterone receptors, or both.
• Patients must be premenopausal.
• Prior anti-estrogen therapy (with or without ovarian suppression)
• Platelet count > 100,000/mm3
• Age older than 18 years
• ECOG performance status 0-2

Exclusion Criteria:

• Hormonal treatment for metastatic disease
• Pregnant or breast-feeding women
• Postmenopausal
• Concurrent hormonal therapy or chemotherapy
• Prior fulvestrant therapy
• More than three prior chemotherapy regimens for metastatic disease
• Concurrent, long-term anticoagulation therapy
• Severe, uncontrolled intercurrent illness
• History of hypersensitivity to castor oil