Drug delivery to tumors of the central nervous system

Contemporary treatment of malignant brain tumors has been hampered by problems with drug delivery to the tumor bed. Inherent boundaries of the central nervous system, such as the blood-brain barrier or the bloodcerebrospinal fluid barrier, and a general lack of response to many chemotherapeutic agents have led to alternative treatment modalities. In general, all these modalities have sought to either disrupt or bypass the physiologic brain barriers and deliver the drug directly to the tumor. This article reviews past, as well as current, methods of drug delivery to tumors of the central nervous system. Special emphasis is placed on biodegradable polymers that can release chemotherapeutic agents against malignant gliomas. A variety of other nonchemotherapeutic drugs, including antiangiogenesis and immunotherapeutic agents, are presented in the context of new polymer technology. Finally, future directions in drug delivery are discussed with an overview on new advances in emerging biotechnology.