Glioblastoma is an aggressive, malignant brain tumor; also known as grow-and-go tumors, they grow very quickly in their original site and they move quickly to new sites in the body. These tumors develop in cerebral hemispheres, but may also appear in other parts of the brain, spinal cord, or brain stem. They stem from glial cells from tissue surrounding the spinal cord and brain.
Symptoms of glioblastoma depend on the location of the tumor, but typical symptoms include: headache, nausea, memory loss, confusion, change in vision, change in speech, change in mood, nerve pain or numbness, and seizures.
Neurosurgeons at the University of California, San Diego School of Medicine are among the first in the world to utilize real-time magnetic resonance imaging (MRI) guidance for delivery of gene therapy as a potential treatment for brain tumors. Using MRI navigational technology, neurosurgeons can inject Toca 511, an investigational gene therapy, directly into a brain malignancy. This new approach offers a way to precisely deliver a therapeutic virus designed to make the tumor susceptible to cancer-killing drugs. â??With chemotherapy, just about every human cell is exposed to the drugâ??s potential side-effects. By using the direct injection approach, we believe we can limit the presence of the active drug to just the brain tumor and nowhere else in the body,â?? Clark Chen, MD, PhD, chief of stereotactic and radiosurgery and vice-chairman of neurosurgery at UC San Diego Health System, was quoted as saying. â??With MRI, we can see the tumor light up in real time during drug infusion. The rest of the brain remains unaffected so the risk of the procedure is minimized.â??
Toca 511 is a retrovirus engineered to replicate in cancer cells, like glioblastomas. It produces an enzyme that converts an anti-fungal drug, flucytosine (5-FC), into the anti-cancer drug 5-fluorouracil (5-FU). After the injection of Toca 511, the patients are treated with an investigational extended-release oral formulation of 5-FC called Toca FC. The cancer cells begin to die when 5-FX comes into contact with cells infected with Toca 511. To ensure that the adequate amount of Toca 511 is delivered to the region of the tumor, neurosurgeons use state-of-the art MRI guidance, called ClearPoint, to monitor the delivery and injection processes in real time. It provides visual confirmation that the desired amount of drug is delivered into the tumor and provides physicians the ability to make adjustments to optimize the location of drug delivery.