Blood-Tumor Barrier Normalization Effects on Cytotoxic Drug Delivery to Brain Tumors

The blood-brain barrier (BBB) restricts delivery of anti-cancer drugs to brain tumors, but the leaky neovasculature of the blood-tumor barrier (BTB) permits systemically delivered cytotoxic agents to reach the tumor. Anti-angiogenic therapies such as bevacizumab (BEV) have been shown to “normalize” brain tumor vasculature,¹ but the impact on chemotherapy delivery remains unclear.² The goal of this study was to use magnetic resonance imaging (MRI) to investigate the consequences of BTB normalization, via BEV, on temozolomide (TMZ) chemotherapy. Non-invasive MRI techniques were used to track the transport of a chemotherapy surrogate, a low molecular contrast agent (Gd-DTPA), in an intracerebrally implanted human glioma. MRI-derived Gd-DTPA concentration curves were fit to a transvascular exchange model to measure vascular permeability changes and were used to quantify initial area under the gadolinium curve (IAUGC) over the course of treatment.