A Phase II Study of Adding the Multikinase Inhibitor Sorafenib (Nexavar) to Existing Endocrine Therapy in Patients With Advanced Breast Cancer

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.