Inclusion Criteria:

- Histologically-confirmed (confirmation done at MSKCC) metastatic adenocarcinoma of
the breast

- Radiologic evidence of new and/or progressive brain metastases (>10 mm in longest
dimension) by MRI imaging of the Brain

- Planned WBRT based on number (≥ 3 lesions) and/or size (≥ 1 cm) of brain metastases.

- Age ≥18 years; males and females

- Patients who require additional clinically indicated stereotactic radiosurgery (SRS)
in addition to WBRT will also be eligible.

- Life expectancy of >12 weeks.

- Karnofsky Performance Status (KPS) ≥ 70%.

- Creatinine ≤2.0 times the upper limit of normal.

- Women of childbearing potential must have a negative serum pregnancy test performed
within 7 days prior to enrollment, must be non-lactating and must agree to use
adequate contraception prior to enrollment and for the duration of study
participation.

Exclusion Criteria:

- Leptomeningeal metastases

- Concurrent administration of lapatinib or other tyrosine kinase inhibitors other than
sorafenib

- Craniotomy or any other major surgery, open biopsy, or significant traumatic injury
within 4 weeks of randomization.

- Concurrent anti-cancer therapy (chemotherapy, hormonal therapy, radiation therapy,
surgery, immunotherapy, biologic therapy, or tumor embolization) other than
sorafenib, and protocol-specified whole-brain radiotherapy.

- Use of any investigational drug within 30 days or 5 half-lives, whichever is longer,
preceding enrollment.

- Inability to comply with protocol and /or not willing or not available for follow-up
assessments.

- Any condition which in the investigator's opinion makes the patient unsuitable for
the study participation.

- Patient is incontinent of urine or stool (which would make them unable to tolerate
lying still for 60 minutes).

- Claustrophobia

- Known allergic reaction to Gd-DTPA

- Renal insufficiency with recent (<3 month old) creatinine >2.0