Washington University’s Eric Leuthardt and others have discovered another benefit of laser surgery for patients with recurring glioblastoma. Credit: Robert Boston / WUSTL Med
The blood-brain barrier (BBB) prevents harmful substances and bacteria from leaving blood vessels and entering the brain—but it also prevents potentially helpful drugs, like cancer therapeutics, from reaching their targets. Now, researchers from the United States report promising pilot trial results using laser ablation to temporarily disrupt the BBB in a small set of patients with recurrent glioblastoma (GBM) for up to six weeks, allowing cancer-fighting drugs to reach tumors in the brain (PLoS One, doi: 10.1371/journal.pone.0148613).
University of Florida College of Medicine’s David Tran, co-corresponding author of the study, says that he and his colleagues hope that their method can help patients with brain cancer live longer by creating a new “window of opportunity” for a whole host of chemotherapy drugs that were once considered ineffective because of the BBB.
GBM is a common and deadly form of brain cancer in adults; people diagnosed with GBM usually die within 15 months of diagnosis. One method for treating GBM is with a procedure called MRI-guided laser ablation, which kills tumor cells by heating them to about 150° F. When reviewing MRI scans from past procedures, the researchers noticed that areas near the former tumor site showed evidence of a “leaky” BBB. Follow-up studies using dynamic contrast-enhancement brain MRI to calculate degree of BBB permeability confirmed that the laser treatment did indeed create a temporary breakdown in the barrier. A permeable BBB could not only allow drugs to reach the tumor, but also provides an opening for the body’s immune system to reach and possibly attack the tumor.
During a pilot trial, the researchers tested their method on 14 patients with GBM receiving laser ablation therapy. After ablation, they treated the patients with doxorubicin—a cancer drug usually blocked by the BBB. Eric Leuthardt, Washington University neurosurgeon and co-corresponding author on the paper, says: “We are encouraged [by the pilot study results] but very cautious because additional patients need to be evaluated before we can draw firm conclusions.” This trial is part of a larger, ongoing phase II clinical trial following 40 patients.