18F-FLT-PET Imaging of the Brain in Patients With Metastatic Breast Cancer to the Brain Treated With Whole Brain Radiation Therapy With or Without Sorafenib: Comparison With MR Imaging of the Brain

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.
* No limit to prior therapies with last anti-cancer treatment ≥2 weeks from initiation of WBRT. Please note: there is no washout period required for trastuzumab, pertuzumab, for patients who have developed new parenchymal brain metastases while on these agents.

Exclusion Criteria:

* Leptomeningeal metastases Please note: leptomeningeal metastases may be allowed if it is limited to cranial metastasis (MRI spine should be completed, within 4 weeks of enrollment, to show that no other leptomeningeal metastases is present) and is not the only metastasis present in the brain.
* 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