German citizen Steffen Rhode spent a year in high school in 1998 studying as a foreign-exchange student in Fosston, Minn. He returned 20 years later with a new hole in his head.

Rhode's return trip last year was prompted partly by his ongoing recovery from a medical procedure to kill a tumor deep in his brain with a narrow laser probe inserted in a pencil-sized tunnel in his skull. The neurosurgeon who treated him in 2017 in San Diego, Dr. Clark Chen, had recently moved to the University of Minnesota, where Rhode visited him.

Physically, Rhode's procedure seems to have worked well. After traditional treatments failed, his procedure with a Minnesota-developed laser ablation system called NeuroBlate appears to have successfully treated Rhode's glioblastoma using a surgical opening so narrow he didn't need stitches afterward.

Now the challenge is surviving survival. Rhode, 37, said he feels he's lost something that people who haven't been forced to examine their own mortality don't even realize they have. And with NeuroBlate patients like Rhode surviving for years after they would have most likely died without the procedure, doctors are starting to consider the long-term emotional, social and cognitive impacts.

"I'm still having a hard time believing that I really survived it," Rhode said in a phone interview. "Basically the whole last year, I was gaining back that trust that I lived longer than I thought. But I'm still not fully convinced. I'm not sure if that ever comes back. … In therapy, we called it the 'naive trust' that you will live for the next years."

Such feelings are not a sign that the procedure wasn't effective — just the opposite. Physicians said that the ablation procedure, performed with the NeuroBlate system designed by Plymouth-based Monteris Medical, has become so reliable at saving lives that it's time to move past survival and start considering long-term quality of life for people who survive "inoperable" conditions.

That's why Monteris has launched a large observational trial called LAANTERN aiming to enroll 1,000 NeuroBlate patients at sites around the nation, including at the U. In addition to tracking medical procedural success, the study is using validated questionnaires to collect data about patients' subjective quality of life (QoL) outcomes.

Chen, who moved to Minnesota to lead the U's Neurosurgery Department, said the idea of doing QoL assessments on NeuroBlate procedures is similar to what unfolded after other cancer treatments proved effective at extending lives.

"If you're dying within six months, the priority ought to be making you live two, three, four years, right?" Chen said. "But once you start seeing patients live out past two, three, four years, then we want to see how we can do even better than that, and improve the quality of life."

Different QoL assessment questionnaires are available in LAANTERN. For patients with central-nervous system tumors like Rhode's glioblastoma, the appropriate survey asks patients to rate how strongly they agree or disagree with statements such as "I have a lack of energy," "I am bothered by side effects of treatment," "My family has accepted my illness," and "I am losing hope in the fight against my illness."

Marty Emerson, chief executive of Monteris Medical, said that gathering such long-term data is part of the company's responsibility to keep generating evidence on its system.

"Many products, including ours, start out as a surgical tool, like a scalpel. Now we are generating clinical data to more accurately describe the potential outcomes from the procedure," Emerson said. "We are approved as a surgical tool, and now our obligation is to generate clinical data to someday be able to talk about outcomes from a disease perspective."

Such data could eventually be persuasive in clinical decisionmaking, Emerson said, as well as help specialty societies write treatment guidelines and aiding payers weighing reimbursement coverage.

Monteris' NeuroBlate system is designed to allow surgeons to operate on difficult and irregularly shaped tumors deep in the brain without open surgery. It includes a long probe that is robotically advanced into the brain under MRI guidance to emit thermal radiation in precise, directional bursts of laser energy that kills tumor cells. The system uses the disposable laser probe and a host of supporting components.

Marketing materials say the NeuroBlate system is used to treat "inoperable" brain tumors, epileptic foci, and necrosis following radiation therapy. Monteris declined to release the system's list price. The cost of a procedure using the NeuroBlate system is covered by the same diagnosis code as a craniotomy, which pays between $23,000 and $33,000.

The system is considered "minimally invasive" because, compared to open surgery requiring removal of part of the skull in a craniotomy, the NeuroBlate probe requires only a pencil-sized tunnel to the lesion. Once in place, the laser probe can be swiveled to project energy in different directions, like a flashlight shining around a dark room. The hole in the cranium under the skin heals after about a year.

"In every centimeter [of brain matter] that we injure or remove during a procedure, there are more neural connections than people in the world," Chen said. "Because of that, there is a significant interest in developing technologies that would not impose the catastrophic effects of open surgery, if unnecessary."

Monteris recently resolved an issue with the device. After the company started receiving reports that the tip of the probe could heat up while under MRI scan, engineers designed and then received FDA clearance for a new laser probe without that problem.

The system first received FDA clearance in 2013, and more than 2,000 medical procedures have been performed with it since then, including the one that Chen performed on Rhode in 2017. Rhode was enrolled in LAANTERN to track his progress after the procedure, but he has since finished the 12-month study time frame.

Chen said that insights from the QoL surveys will help physicians provide better long-term care for the people they operate on. Should some patients be automatically referred for mental health care after the procedure? Are anti-depressants the right answer for someone who is going through appropriate post-surgical stress and has family support at home?

Chen said that the time has come for surgeons to start thinking about longer-term questions like these, and many more.

"Now that we see there is improvement in survival, the onus is on the physician to not just see their survival, but see how well they're doing in that survival, so that we can make a difference," Chen said.

Joe Carlson • 612-673-4779