A real-time MRI scan enables neurosurgeons to target the tumor.
According to the American Cancer Society, most people will survive just 15 months following diagnosis of this kind of tumor, because it is so difficult to treat.
Laser heat is known to kill brain tumor cells, and now it seems that the technology can also penetrate the blood-brain barrier.
Co-corresponding author Dr. Eric C. Leuthardt, a professor of neurosurgery at Washington University in St. Louis, MO, was part of a team that developed the technology.
It was approved by the Food and Drug Administration (FDA) in 2009 as a surgical tool to treat brain tumors, but this is the first time it has been shown to disrupt the blood-brain barrier.
Surgery takes place as the patient lies in an MRI scanner, giving the neurosurgical team the chance to observe the tumor in real time.
After making an incision of 3 mm, the neurosurgeon robotically inserts the laser, which kills the tumor cells by heating them to around 150 °F.
Tumor growth stalled during treatment
The researchers anticipated that the heat would kill the tumor cells, but they were surprised to find, while reviewing MRI scans, that changes had occurred near the former tumor site that indicated a breakdown of the blood-brain barrier.
The laser treatment kept the blood-brain barrier open for 4-6 weeks, which presented a window of opportunity to deliver chemotherapy drugs.
The current research is part of a larger phase 2 clinical trial with 40 participants. The current study originally enrolled 20 patients, of whom 14 were deemed suitable for the trial.
The 14 candidates underwent minimally invasive laser surgery to open the barrier, and 13 of them received a widely used chemotherapy drug, doxorubicin, delivered intravenously over the following weeks.
In 12 patients, the tumor did not grow during the 10 weeks of the study. One patient's tumor grew before chemotherapy, and another's progressed after the treatment.
Researchers are continuing to monitor the patients' progress.
The laser surgery was well tolerated by the patients, most of whom went home after 1-2 days. There were no severe complications.
Dr. Leuthardt says:
"Our early results indicate that the patients are doing much better on average, in terms of survival and clinical outcomes, than what we would expect. We are encouraged but very cautious because additional patients need to be evaluated before we can draw firm conclusions."
Previous attempts to break the barrier have either provided a window of only about 24 hours, insufficient for consistent delivery of chemotherapy, or had limited benefits.
Not only does the laser technology leave the barrier open for long enough to deliver multiple doses of chemotherapy, but it also opens the barrier near the tumor. The protective cover remains intact elsewhere, limiting the harmful effect of chemotherapy.
On the basis of these findings, the team speculates that alternative approaches, such as cancer immunotherapy, could also be used for patients with glioblastomas. Cancer immunotherapy involves harnessing immune cells to seek out and destroy cancer.
The researchers are next planning to trial the laser technology together with both immunotherapy and chemotherapy.
Medical News Today reported last year that mapping proteins could enable experts to track the regrowth of brain tumors.