There’s a reason “brain surgery” is used as a de facto standard for anything difficult. It’s really tough — even for brain surgeons.
Extreme precision is clearly needed, along with a method for accessing tumors that may be lodged deep in the brain. A non-invasive approach makes sense, but that’s easier said than done.
On Wednesday, at the 2017 American Association of Neurological Surgeons (AANS) Annual Scientific Meeting, Monteris Medical will present new data that confirms it can be done, across multiple centers. Surgeons using the NeuroBlate System were able to perform minimally-invasive brain surgery on a range of tumor locations, the analysis shows, including many that were deemed inoperable.
In a phone interview, Andrew Sloan, director of the Brain Tumor & Neuro-Oncology Center at the University Hospitals Cleveland Medical Center and a consultant for Monteris, discussed his two presentations at AANS and how the field has advanced.
The data come from a retrospective analysis of surgeries performed in nine centers from 2011-2015. The oral presentation describes the results of 97 patients whose lesions were ablated with the NeuroBlate System. Of the lesions analyzed, 48 percent were deep-seated, 57.8 percent were considered inoperable, and one percent were not suitable for chemotherapy.
A poster – which earned the ‘Third Place Tumor e-Poster Award” – reports on the same study but follows 40 patients who had brain metastases (cancer that has spread from another organ). In that group, 32.5 percent were considered to be inoperable, 10 percent were unable to tolerate radiotherapy, and 2.5 percent were unable to tolerate chemotherapy.
“This is not a matter of ‘will I take my red car or will I take my blue car?'” Sloan explained. “This is a matter of ‘can I do this or is it not feasible to even do anything?'”
Surgical teams have tried non-invasive surgery before, with radiation and more recently with laser technology. The challenge is always getting control and insight into what’s happening at the tumor site, Sloan stated.
“There were three inventions that really made this technically feasible,” he said.
The first is the invention of a laser that can be turned on and off. Entering the brain with a burning laser could have devastating results, depending on what tissue is impacted. Monteris Medical’s lasers are gas-cooled and fully responsive (they’re controlled with a foot pedal), heating and cooling on cue.
The second innovation is called MRI thermometry. Magnetic resonance imaging (MRI) machines have become more and more powerful, generating vivid images. However, until recently, they couldn’t track heat. MRI thermometry was created to show temperature changes in real time, allowing absolute precision when ‘cooking’ the tumor. That’s especially important, Sloan said, because heat directed at a tumor doesn’t emanate outwards in an even manner.
Both are significant advances, but one more problem remains.
“If you could treat every tumor in one application, those two would do it,” Sloan said. “But most of my tumors are big and I cook part of the tumor and then I have to move my laser and I cook another part of the tumor.”
Given the precision required (for example, the operation may call for 10 minutes of heating at 43 degrees at specific coordinates), surgeons need to know exactly what tissue they have heated and for how long. No human can keep track of the three-dimensional areas hit, Sloan said, when the tumor is targeted from multiple angles. This problem is solved with software associated with the NeuroBlate System, which can track a surgeon’s work in real-time.
Combined, the innovations put on quite a performance. During the surgery, a neurosurgeon robotically inserts a laser catheter towards the site of the tumor. The laser is inserted at body temperature and then pulse-heated to exclusively kill the tumor tissue. The procedure is monitored throughout via data transmitted from an MRI into the dedicated software platform.
Surgery has definitely come a long way from a technology standpoint, but Sloan argues that the fundamentals remain the same.
“I had one of my residents tell me it that wasn’t really surgery because you’re not using your knife,” he said. “So the question is: What is surgery? To me, surgery is modulation of a tissue using energy. The majority of it is taking a sharp stainless-steel blade and exerting mechanical energy to cut tissue… Radiosurgery or LITT is the same way; we’re taking laser energy and we’re precisely focusing it to kill tissue. I think you have to be a surgeon to do that.”
So what of the outcomes?
Overall survival in the glioma group was 564 days (approximately 18.5 months), Sloan reported, noting that the bulk of patients in the analysis had glioblastoma (GBM), the most common form of the disease.
“That’s pretty amazing when you consider that for a newly diagnosed GBM… the median survival is only about a year and when they recur it’s only about 6-9 months,” he said. “Especially for a non-invasive approach.”
A lot of these patients had recurrent GBM and had been previously treated for their primary tumor, he said.
The brain metastases group performed a little worse, with a median survival of 421 days (approximately 13.8 months). However, less than five percent of the patients died from their brain tumors. Brain surgery can’t treat the primary tumor, after all.
“In the old days, even 10 years ago actually, if you had a brain metastasis, you were probably going to die from the brain metastases,” Sloan said.
In terms of collateral, Sloan said the damage beyond the laser catheter and cranial entry point is minimal. Some patients showed a minor cognitive decline after the operation and recovery.