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Melanie Cole MS (Host): Welcome to UF Health MedEd Cast with UF Health Shands Hospital. I'm Melanie Cole and joining me today to highlight the role of laser ablation in the treatment of brain tumors is Dr. Maryam Rahman. She's an Associate Professor in the Lillian S. Wells Department of Neurosurgery at the University of Florida College of Medicine.

Dr. Rahman, it's such a pleasure to have you join us today. Before we get into this really interesting topic; I understand that you were the first female president of the Florida Neurological Society and served on the Executive Committee of the Congress of Neurological Surgeons. Can you tell us a little bit about that, please?

Maryam Rahman, MD, MS, FAANS: Thank you for having me, Melanie. And both of those statements are true. And it was truly an honor and a privilege for me to be chosen for those positions. And honestly, was, I would say due to tireless work of many, many people who came before me to set the stage to make that possible.

Host: Well, thank you for telling us about that. So now we're talking today about laser ablation in the treatment of brain tumors, gliomas. Can you tell us a little bit about the role of it? How does laser ablation differ from traditional surgical methods for treating these gliomas? And tell us just a little bit about it.

Maryam Rahman, MD, MS, FAANS: Laser ablation has been around for about 10 years now for the treatment of brain tumors. And, there's nothing new about putting a laser into tissue and burning a tumor. That technology has existed for decades. But previously we had no ability once we placed the laser into someone's skull to know what temperature we were reading, how much tissue was being ablated, and so it was really just kind of guesswork and therefore was not safe to do on a routine basis.

What changed recently were two things. One was technology developed that allowed cooling of the outside of the laser as you deliver the laser energy so you can kill tumor cells by generating heat without getting charring of the tumor cells onto the tip of the laser by cooling the inside of the laser either using carbon dioxide or saline that continuously runs through the laser.

And the other technology that really made this a treatment modality for patients was the ability to infer temperature within the brain using MRI. And so these procedures are typically performed in the MRI suite. And we, here at University of Florida have an intraoperative MRI where we perform these procedures. And so when we have the laser in someone's brain tumor and we turn the laser on, the patient's actually in the MRI scanner and we're getting continuous imaging on that patient that allows us to see what temperature we're reaching within the tumor.

 And so, based on some physics and some equations, then we have a calculation of when we've received a high enough temperature for long enough that this resulted in tumor cell death. And that's how we know when to stop.

Host: This is so interesting. What an exciting time with advancements in your field, Dr. Rahman. Thank you for telling us about those delivery methods and also the intraoperative imaging and the role that that plays. So tell us a little bit about patient selection. What are specific type of brain tumors that are most suitable for laser ablation and are there some patients for whom it is contraindicated?

Maryam Rahman, MD, MS, FAANS: Laser ablation it's a little bit agnostic to the type of tumor, but we typically treat malignant brain tumors, whether that's primary malignant brain tumors like glioblastoma or other malignant gliomas or brain metastases which are cancer that has spread from somewhere else in the body to the brain such as breast cancer, colon cancer, lung cancer that then breaks off and goes into the brain.

Typically the ideal patients to treat with laser ablation are patients that have tumors that are three centimeters or smaller. Once they get larger than that, you can treat with laser ablation, but it usually requires us to use more than 1 trajectory. Like, we have to put more than 1 laser in to get full coverage of the tumor.

And what we're doing with the lasers, we're burning the tumor. It's dying. And then your own immune system comes in to remove those dead tumor cells. So there's, uh, kind of a dual benefit. You get an immune activation at the site of the laser ablation and you directly kill tumor cells.

The downside of that, is that you get brain swelling after laser ablation. And so if you're treating a very large tumor, that brain swelling can be dangerous for patients. And so that's why we typically treat lesions or tumors that are in the medium to small range. And so the other potential benefit of laser ablation is that we can treat tumors that are in deep locations because we're using a very small laser to access the tumor through a very small hole.

So in that regard, it is minimally invasive. And so in locations where we typically couldn't safely get there from a surgical standpoint, we can get there safely with a laser. And so patients with deep tumors that are medium to small in size and are malignant; are really the ideal patients for laser ablation.

Patients that would be excluded are patients with larger tumors that should probably get surgically resected, they're more on the surface, or anyone who has a contraindication for being in an MRI scanner. If they have some type of metal or implant in their body that precludes them from getting an MRI, we would not be able to perform the laser ablation.

Host: Dr. Rahman, as you're speaking to other providers that may or may not be looking to do laser ablation, do you have any technical considerations you would like to mention and how much does the experience of the surgeon matter for laser ablation?

Maryam Rahman, MD, MS, FAANS: Experience, like most things in neurosurgery, is everything, and laser ablation is a relatively newer technology, and the challenges in laser ablation are very, very different than what we would experience in the operating room performing open surgery. And so, there is a relatively steep learning curve when you start performing laser ablation.

The nice thing is that the neurosurgeons across the country who perform these procedures, most of us are all friends with each other. We share experiences with each other, we publish on this. And so, that allows for us to learn faster and to try to avoid the potential pitfalls associated with stereotactically implanting a laser into someone's tumor and then delivering laser ablation within the MRI scanner.

And in terms of sharing experience with other people who would want to start a laser ablation program in their center, I think honestly, going to other institutions, seeing how people do it, how the setup is, because everyone does it a little bit differently depending on what tools they have available at their institution, would probably be the fastest way to get going.

And then also having some of the senior folks who perform these routinely come out to their institution to watch their first few cases or to help them is usually the best way to go.

Host: That's great advice. And Doctor, when we think of reaching out, and as you say, reaching out to other institutions, which has really been an advancement in medicine all around instead of working in that silo. There's much more research sharing going on. Speak a little bit about the multidisciplinary approach and the interdisciplinary approach that goes into the surgical decision making for gliomas and everyone involved in the pre process and after.

Maryam Rahman, MD, MS, FAANS: It's everything, right? Teamwork is everything, especially in today's day and age. Delivery of healthcare is so much more complex, and so doing it without a team is impossible, and, a personal value of mine is really removing barriers to sharing knowledge, and so, there's no downside to sharing information, sharing your research, sharing figures. The more you give, the more you receive, I truly believe that.

But in terms of the interdisciplinary component of this, UF, we have a very large brain tumor center here where we integrate clinical care, research, and education. And most of that is housed within the department of neurosurgery, including the neuro oncology piece of this. And so for these patients, they're usually shared patients between myself, neuro oncology, and radiation oncology. Both myself and the neuro oncologist see these patients together in clinic and come up with a comprehensive plan prior to performing surgery. And that's usually a combination of chemotherapy or immunotherapy with the laser ablation.

Sometimes we time it such that they get their first dose of immunotherapy before the laser ablation so we can activate their immune system even before we cause tumor cell death and trying to take advantage of that immune activation that happens after laser ablation. And so, it's very important.

The other thing is that there are patients who may not be a candidate for laser ablation for some reason or another. And so we want to make sure that we have the opinions of our radiation oncologist and the neuro oncologist on board so that we have other backup plans for these patients if they cannot receive laser ablation.

And then, of course, post laser, these are mostly malignant brain tumors, so they're going to be continuing on some therapy with a neuro oncologist, and they are going to be followed with them. And so, this is all teamwork between myself and those providers, including the nurses who obtain the authorization for the chemotherapy, the social workers who help patients get to and from their appointments and help their caregivers.

And so without the team, none of this would be possible.

Host: Well, thank you for that. And Dr. Rahman, as we wrap up, what do you believe are some of the future prospects of laser ablation as a mainstream treatment option for these gliomas and potential future directions? Give us a blueprint for future research.

Maryam Rahman, MD, MS, FAANS: Laser ablation has, I would say, a real but limited role overall in the treatment of brain tumors. It has a particular role to play for medium to small tumors in deep locations. And it is just one other thing we have added to our armamentarium to fight brain cancer. And so in that way, it's very powerful.

The research applications of laser are very interesting, and it's because the delivery of heat energy to a tumor within the brain is a unique treatment modality for us, and it results in completely different physiology within the tumor microenvironment compared to other traditional therapies such as surgical resection, ionizing radiation, or chemotherapy.

And what we are currently investigating, both in our human patients and in my laboratory, where we've created a laser ablation system for mice, is the ability to open the blood brain barrier, which is the natural brain's defense system against toxins but limits how chemotherapies can get in to tumors.

And so we're currently investigating using the laser to open the blood brain barrier, because we know it does that for several weeks post laser ablation and then delivering a personalized medicine chemotherapeutics to the animals to see if we really get increased concentrations within the tumor.

And if we do, that then lends itself to this idea that all these chemotherapies that we currently cannot use for brain tumors, because they do not cross the blood brain barrier will now become potential treatment options for patients. And so that is currently being investigated in our laboratory in collaboration with U.S. Scripps and Jupiter, with a collaborator of mine there named, Tim Spicer, who's excellent. And, depending on the results, we are very enthusiastic about potentially then taking this to test in human patients.

Host: Thank you so much, Dr. Rahman, for joining us today, sharing your incredible expertise on this topic. And to learn more about this and other healthcare topics at UF Health Shands Hospital, please visit innovation.ufhealth.org. r Or to listen to more podcasts from our experts, please visit ufhealth.org.medmatters.

And that concludes today's episode of UF Health MedEd Cast with UF Health Shands Hospital. Please remember to subscribe, rate, and review UF Health MedEd Cast on Apple Podcasts, Spotify, iHeart, and Pandora. I'm Melanie Cole. Thanks so much for joining us today.