Dr. Tatsui is coming up next to discuss laser ablation for spinal tumors. Hi, thank you for the invitation, it's a pleasure to be here. We're going to be talking about the use of a new modality of separation that is minimally invasive. We have a consulting agreement signed with Medtronic that might be pertinent for this talk. So, this was presented by Dr. Kazma and Dr. Bielski. This is the part of the study that basically proved that surgery, when combined with radiation, provides a better result than radiation and is the grounds for us to support the utilization of surgery in the management of patient's spinal metastasis. In a case like this, where you have severe degree of spinal cord compression, you have spinal instability, that's the type of operation that the PACHO study provides data for us. So, we can tell that this individual is going to be the best chance for him to remain ambulatory, to decrease his narcotic usage, to remain continent, is to undergo such an operation like this. And, unfortunately, some of our patients, they are not fit to undergo an extensive operation. As Dr. Bielski said, the biggest revolution that happened in neuro-oncology, in spine oncology, would be development of stereotactic radio surgery. And now, we don't have the concept of radio resistance to conventional radiation. This is a study that was performed in MD Anderson. It was performed in our 332 patients, and our local control rate was 88%. However, these guys here, they were not with high grade compression, cord compression. They were all with low grade cord compression. And, at this study, we didn't classify those patients according to the Bielski classification. I think that every single study on stereotactic radio surgery should use this classification because that predicts the failure if you have high degree cord compression, as Dr. Bielski showed. So, I'm going to go shift gears and show cases where I believe this technology can be applied. This is a patient with 59-year-old. Renal cell carcinoma has failed several first-line therapies, first, second, and third-line therapy. His KPS is 60% because he's recovering from resection of a cerebellar metastasis. And he has progressive disease in his lungs, liver, and adrenal gland. And he comes with a spinal cord compression, a grade 2, or grade 1C, if you will, and a severe osteolytic lesion here. So, this would be a KPS, 60%, as seen in the score that Dr. Gokasman showed, is 8, potentially unstable. And what should we do? So, not all patients are fit for surgery. You can add other variabilities that some of these guys have, like anticoagulation, comorbidities, and you have a high surgical risk here. So, according to the NOMS framework, this patient should receive either stereotactic radio surgery or surgery. However, if they are not able to tolerate surgery, our result in terms of local control becomes meaningless if the patient is not going to survive the operation. So, because we face this quite often, I had contact with this technology being applied on the brain, and we adapted it to the spine. We received some attention, and we were able to publish on the main journals of our specialty. And basically, the concept is we have this fiber optic catheter that emits laser on the tip, and we could insert this in the spinal tumor, and we could use MRI to monitor this in real time as we damage this part on the epidural component here. Titanium artifact precludes us to do this monitoring, so we can't use this in a post-operative setting when you have spinal instrumentation. So, basically, the idea is that we have this epidural component here that would require a surgery to be removed. We could potentially put our laser catheter there, destroy this tumor, and that would be equivalent to perform separation surgery. So, this is an example here. So, I have this patient with cholangiocarcinoma. Contact BIOSCII-2, displacing the spinal cord. In our institution, our constraints to the cord is 12 grays. We want to hit this with 24 grays of radiation. And there is a zone here where we're going to have to underdose, given the need to respect these constraints of the spinal cord. If we perform laser ablation of this epidural component, this is the result that we get right after we finish. Before the patient wakes up, we can get an MRI with contrast, and we can see the zone of coagulation here on the epidural space. We can then plan a radiation respecting the constraints of the spinal cord, and we can achieve local control similar to separation surgery, if you will. So, with this concept, we have treated 105 patients. We started in 2013. Our failure rate has been 16%. We had six patients that we had to do decompression because of tumor progression and development of paresthesias. I have four patients that were so sick to undergo conventional surgery that I treated with another laser ablation and was able to control the disease. And I had six patients with failure, radiographic failure, but they went to hospice care because they were so sick to undergo surgery. The median time to failure was five months, and our complication rate was 10%. Out of these complications here, I had two nerve root dysfunctions in patients where we did this in the lower levels on the lumbar spine, where we couldn't identify the nerve roots on the lateral rhesus and foramen. So, we stopped doing that on the lumbar spine. We're doing only on thoracic from T2 to T12. We changed our institutional permission to do cases only on those levels. I had three of my decompressions happen within 30 days, so I considered a complication here. We had some minor infections. One of our infections was a little more severe that required antibiotics and was an epidural phlegmon. And one patient had a cerebellar stroke, and he had atrial fibrillation. So, showing the current workflow, this would be an example of a patient with T12 tumor, a renal cell carcinoma newly diagnosed with severe radiculopathy and mechanical pain. So, we do this in our intraoperative MRI, and we use this transfer table to move the patient in and out of the high-power magnetic field so we can use our non-magnetic instruments. We have to put these fiducial markers in the zone of interest, and we mark a skin incision for the spinal process clamp for the image guidance. After we apply the spinal process, we cover with a sterile towel. We cover our fiducials with MRI coil, and we go into the MRI machine. We get T2 sequences, and we register the MRI into the navigation software, and then we perform surface matching. We attach our reference array and perform surface matching, and this is the image guidance that we can use for the catheter implantation. So, this is the first time MRI has been used with this purpose. Intraoperative MRI has been used with this purpose, and this is a video showing how we do it. It's very similar to placement of percutaneous pedicle screws. So, we use a small incision, and then we use a navigated needle to enter the tumor. Once we reach our target, we can exchange the needle into a K-wire. I like always to confirm the location, because it's a percutaneous procedure. I don't have parameters to confirm if I'm accurate when I'm going deep, so I like to stop in the pedicle and use an x-ray to confirm my location. After I confirm, I advance to the final target, and then we can exchange the gem sheet needle into a plastic cannula that will maintain the trajectory. So, as you can see, we're treating a renal cell carcinoma here with very little bleeding, and once we put our catheter, our access cannula, we put a little titanium needle that we tap a little bit to maintain our trajectory. Usually, I use catheters in tendon. Every catheter can cover one centimeter of tumor. If I have a three-centimeter tumor, we use three catheters in tendon. After we finish our placement, we then cover everything with sterile towels, and then we're going to insert our laser catheter. So, in order to get the MRI images, I need to put the MRI coil in there. So, I'm adding the coil, and then I cover everything with sterile towels, and then we add our laser catheter, and then we can proceed to the MRI for localization of this catheter. So, after I have my catheter in there, we attach everything to the sterile field. We need to connect the irrigation system so the laser doesn't carbonize the tissue. That's another thing that we do. It's cooled with saline, and we keep the temperature between 60 to 90 Celsius. So, after we finish, we go to the MRI, and we localize our catheter. So, this is the predicted location, and this is the location that we found the catheter. As you can see here, one catheter is not enough to cover the entire tumor, so we have to add a second and sometimes even a third catheter. So, once I'm satisfied with my coverage of my tumor, we go then for the treatment phase. The ideal distance between the dura and the catheter should be something between 6 to 7 millimeters. So, we localize the location on the axial plane of every catheter, and then we use the system to select the pixels here on the axial image in the center of the catheter where we want to monitor the temperature. I could monitor anywhere here, but my place of interest is really the epidural space. So, I use my high limit to stop the system if the tissue gets carbonized, and we select points here on the junction between the dura and the tumor, and we set this limit to 48 Celsius. Then, we have our anesthesiologist in the room. We ask them to stop the ventilation for two minutes because the ventilatory motion creates artifact, and this is the real-time laser ablation here, showing that you can see that the heat can be monitored in real-time, virtually almost near real-time, and the temperature, once it gets to the limit that I set here, like 48, will strip and stop the system. So, I was able to burn or to ablate all this tumor that is in the epidural space here, and this is, as we are doing this, the computer is creating a mathematical model of damage, and this yellow pixel, every yellow pixel here is some temperature that reached a cell Q limit, and correlating this to the immediate post-operative MRI scan shows a nice correlation between the predicted zone and the ablated zone here, and that's the spinal cord here, showing that we were able to destroy all the tumor that was compressing the spinal cord here. So, this is a reconstruction. This is the top plane. This is the lower plane, showing that we were able to perform a good decompression or good ablation of the epidural tumor, and we were able to achieve ablation from the entire cranial caudal extension. After we complete this, if the patient has instability of the spine, we can re-register the navigation software, and we can put percutaneous screws, and I'm using more and more these fenestrated screws where I can inject cement and perform short segment stabilizations on these cases, obtaining very good results. This is the patient two days when she left home after this operation. She was very happy, making thumbs up. Her pain has significantly improved. Once we burn the ganglion, I think there is an immediate improvement in pain, and this is the six-month follow-up showing a very good result here in terms of local control. So, I believe that this result is the similar result that I would have achieved if I had done open surgery to her. So, I looked in our series, two cohorts that are not matched, but they represent a surgical group, and they represent a group of patients that I treated with laser. On the top is a case where renal cell carcinoma, where we treated with laser ablation. Actually, that was my first patient, and we show a local control here in 12 months. I consider this success. This is an example of renal cell carcinoma that we performed surgery, and this is the local control after 12 months. So, all these patients underwent surgery and then stereotactic radiation, and these two groups I considered. I tried to compare these groups. There was a discrepancy in the amount of spinal cord compressions. We have, like, two-thirds of my patients on the surgical group were Bilski 3 classifications, opposed to two-thirds were Bilski 2 on the treatment group that I used LIT. And this is an example of failure. So, we look into cases like this, where we had a Bilski 2 compression, we treated, became a Bilski 0, and then we have here, after some time, you know, worsening of the Bilski degree. So, we consider this failure similar to our group of surgical group, where we treated these patients, and then the spinal cord, the Bilski classification got worse as the time passed. So, looking these two cohorts, I found that most of my failures happened when my catheter was not positioned on the adequate distance between the epidural space and the tumor. So, this is an example where I wanted to put my catheter here, and the catheter was way far lateral, and my ablation was not centered where I wanted. So, this dark spot here should be here, where the arrow is, instead of here. If I leave more than 5 millimeters of tumor here, no surprises. You know, this is where the tumor gets underdosed, and then I don't have the local control. So, this is one of my patients that I had to decompress after the treatment. So, looking on these two cohorts that are not matched again, we are looking at, they are not the same in terms of compression, but I can infer that I can have a less invasive procedure by having a lower amount of blood loss. So, our blood loss was 100 cc versus 1,100 on the open group. Our hospital stay was 3.5 days versus 12 days. The days to initiate radiation, 1.8 versus 40 days. I have to say that most of this radiation here has been preplanned, so it can be delivered right away after the procedure, different than the open group where then you have to do a CT myelogram, and then you have to simulate the patient, and you need to allow some time for the wound to heal. And days to return to systemic treatment, 3 weeks versus 60 days, and that has been very significant. In terms of decompression of the cord, surgery is way more effective. We were able to get all our BSK3s for BSK0, like expected with surgeries, and the laser ablations was able to decrease one BSK scale, but from a BSK2 to a BSK1B, that's a big difference in terms of control of the tumor. And our morbidity was lower with LIT versus with surgery. We had a 12% morbidity versus 28%. I'm going to say that out of these here, 24, 7 patients, they never left the hospital because they had failure to thrive after surgery. So in our group of patients here, they were actually sicker than this group here. And when we plot the local control, there was no difference in terms of local control. We're getting around 80% on the vertebractomy and 77% local control on the LIT. And again, these are not matched cohorts. So this gives us grounds to pursue a prospective study where we could compare these two techniques. So going back to my first patient where I thought that surgery could be too much for this guy, instead of doing surgery, we performed LIT, we performed stabilization, and then we performed our laser ablation. This is the immediate post-op, and this is the patient two days when he went home after this procedure. He was fully recovered. And this is the five-month follow-up showing that we were able to perform adequate decompression of this patient. So in conclusion, we are showing that we can have a short interval between the surgical procedure and the stereotactic radiation and the oncologic management with chemotherapy. We have a short hospital stay. We have lower morbidity. And the question that remains to be answered is if we are achieving similar local control to surgery. And even another question that I want to answer is that, do we need to do LIT? As stereotactic radiation is getting better and better, we are understanding more of the constraints of the spinal cord. Maybe the future trial that we will be doing will be just radiation versus radiation with LIT, like a modern partial trial version of it. So thank you very much. Thank you, Dr. Gatsui.

laser ablation

spinal tumors

surgery combined with radiation

cholangiocarcinoma

intraoperative MRI