Inclusion Criteria:

• All subjects must be female.
• Age ≥ 18 years old.
• Histologically proven carcinoma of the breast.
• Estrogen receptor and/or Progesterone positive disease.
• Metastatic or locally advanced disease.
• Patients on a preexisting endocrine agent for at least 3 months before enrollment.

• Have residual measurable disease after

  1. maximal response to endocrine therapy or
  2. no response to endocrine therapy or
  3. progressive non-visceral disease on endocrine therapy.
• Must be able to provide a tumor block from either the primary or metastatic site, if available.
• ECOG Performance Status 0-2.
• Adequate organ function.

Exclusion Criteria:

• Patients with rapidly progressive disease on endocrine therapy who would otherwise be candidates for chemotherapy.
• Other coexisting malignancies, with the exception of basal cell carcinoma or cervical carcinoma in situ.
• Prior use of anti-angiogenic agents.
• As judged by the investigator, uncontrolled intercurrent illness.
• Known brain metastasis. Patients with neurological symptoms must undergo a CT scan/MRI of the brain to exclude brain metastasis.
• Treatment with a non-approved or investigational drug within 30 days before Day 1 of study treatment.
• Concomitant use of phenytoin, carbamazepine, rifampicin, barbiturates, or St John's Wort.
• Known or suspected allergy to sorafenib or any agent given in the course of this trial.
• A serious non-healing wound or ulcer.
• Evidence or history of bleeding diathesis or coagulopathy.
• Major surgery, open biopsy or significant traumatic injury within the 4 weeks prior to the first dose of the study drug.
• Pulmonary hemorrhage/bleeding event ≥ CTCAE Grade 2 within the 4 weeks prior to the first dose of study drug.
• Pregnancy
• Any condition that impairs patient's ability to swallow whole pills.
• Documented malabsorption problem.