Study Bendamustine Concurrent Whole Brain Radiation Brain Metastases From Solid Tumors

The purpose of this study is to: * Test the maximum tolerated dose (MTD) of Bendamustine with whole brain radiation therapy (WBRT) * To determine the plasma pharmacokinetics (a blood test to see how much of the drug is getting into the patient's system and how long it lasts in the system) of Bendamustine * To determine the presence of Bendamustine in cerebrospinal fluid (CSF) (fluid from the brain and spinal cord) of study patients Bendamustine is approved by the Food and Drug Administration (FDA) for chronic lymphocytic leukemia. However, Bendamustine will be used in this study as an investigational agent.