Vascular factors affecting drug delivery to brain tumors

This paper will briefly review the vascular factors that are important in selecting an agent for BNCT. In general, these particular factors - tumor blood flow and microvascular permeability - have not been considered critical limiting factors in BNCT. Although the normal cerebral capillary endothelium restricts the transfer of water-soluble drugs from blood to brain, the capillaries of malignant cerebral neoplasms are generally more permeable. Furthermore, blood flow in malignant brain tumors is generally normal or even increased, except in necrotic regions in which drug delivery is considerably less important. Unfortunately, these generalizations may be inadequate for any form of drug therapy which is delivered by the bloodstream and which seeks to entirely eradicate a malignant brain tumor. Available multi-modality treatment programs fail to achieve a cure despite the fact that they can eliminate more than 99.99% of a tumor. Thus, novel forms of therapy are not needed for the vast majority of the tumor cells. Instead, all new forms of therapy, including BNCT, must concentrate on the .01% of tumor cells which are presumably different enough to escape destruction