The purpose of this study is to evaluate the safety and tolerability of oral Dichloroacetate (DCA) in the treatment of recurrent malignant brain tumors (RMBTs). RMBTs are defined as either: 1) malignant tumors, originating in the brain, that have recurred at least once or 2) malignant tumors originating elsewhere in the body that have spread to the brain at least once. Otherwise, there are no limitations to the number of prior recurrences. There are no limitations to the number or types of prior therapies.