Stereotactic Laser Ablation Research Articles

An Unusual Case of Hypothalamic Hamartoma With Nongelastic Seizures and Posterior Cortex Connectivity

BackgroundTo describe a rare seizure semiology originating from a hypothalamic hamartoma in a child, along with unusual ictal onset and connectivity pattern, and provide a review of the pathophysiology of epilepsy associated with hypothalamic hamartoma and management. MethodsA detailed retrospective chart review and literature search were performed using Pubmed and Embase. ResultsWe present a case of a three-year-old male who presented with dyscognitive seizures with onset at age 22 months. Stereoelectroencephalography exploration confirmed the onset in hypothalamic hamartoma with rapid propagation to the temporal-parietal-occipital association cortex and precuneus. The patient's epilepsy was cured with laser ablation of the hamartoma. ConclusionPublished literature mostly describes a more anterior frontal or temporal epileptic network with primarily gelastic seizures being the hallmark type of seizures associated with hypothalamic hamartoma. We highlight a rare posterior cortex network with an atypical presentation of focal nonmotor seizures with impaired awareness in the setting of a hypothalamic hamartoma. Stereotactic laser ablation of the hamartoma rendered seizure freedom. Early diagnosis and appropriate treatment can lead to seizure freedom.

Laser Interstitial Thermal Therapy (LITT) for Neurosurgical Procedures: Facts You Need to Know About the Anesthetic Management of LITT Procedures.

The field of medicine is constantly advancing to improve patient care. As physicians, we must improve our knowledge by listening, reading, and practicing evidence-based medicine. Laser treatment has evolved over the years in many surgical specialties. Laser interstitial thermal therapy (LITT), also known as stereotactic laser ablation (SLA), was developed in neurosurgical procedures to treat recurrent or metastatic brain tumors, radiation necrosis, and epilepsy lesions. LITT procedures are advantageous in providing better patient outcomes, decreased hospital length of stay, and reduced total hospital cost. These procedures are performed as a multi-disciplinary approach; this article discusses the different types of LITT systems, indications, contraindications, types of anesthesia, perioperative anesthetic management,safety precautions, complications, recovery during and after LITT procedures, and the future of LITT procedures.

LMAP-09 RECAPITULATING LASER INTERSTITIAL THERMAL THERAPY IN PRECLINICAL BRAIN TUMOR MODELS

Abstract Laser interstitial thermal therapy (LITT) is a minimally-invasive option for cytoreduction of recurrent or otherwise difficult-to-access intracranial tumors. Relative to resection, ablated tumor tissue remains in situ, facilitating recognition of tumor antigens and a targetable immune response. To investigate the immune consequences of LITT, we developed a model of stereotactic laser ablation for use with existing syngeneic glioma and intracranial metastasis cell lines. A 1064 nm diode-based Nd:YAG laser (Monteris Medical) was used to thermally ablate normal brain tissue or CT-2A tumors in C57BL6/J mice. Ablations were performed at 10 days post-implantation at + 2 ML, + 1 AP, -3 DV using a stereotactic frame. Simultaneous temperature measurements were taken using a thermocouple probe implanted to the same depth 2 mm posterior. We first used serial T2-weighted MRI imaging to accurately track the tumor growth characteristics and identify a safe lesion size for ablation, selecting 10 days post-implantation for subsequent experiments and 2 mm posterior as the ideal position to monitor temperature at the lesion edge. To assess the thermal characteristics of our laser, we ablated mouse brains at 1 W and 2 W for 30, 60, or 90 seconds each, finding that 1 W for 90 seconds produced an ablation that did not char or coagulate tissue outside the ablation zone and recapitulated human ablation findings on H&E staining 24h post-LITT. We next implanted CT-2A tumors for ablation with the selected dose, following mice for survival between the LITT and sham-ablated groups. A subset of mice were imaged using T2-MRI at 1, 3, 7, and 14 days post-surgery. Our model recapitulates the essential clinicopathological findings of LITT and is well suited apply to a variety of intracranial tumor models and LITT-adjunctive therapies.

Intraventricular SEEG and laser ablation for the treatment of infantile spasm: Technical note.

Infantile spasm (IS) is an epileptic encephalopathy with ongoing neurological damage due to seizures and epileptiform abnormalities. Epilepsy surgery is considered for children refractory to drug therapy, especially when there is a focal brain lesion. In this study, we investigated the feasibility and efficacy of intraventricular stereotactic electroencephalography (SEEG) and laser ablation for the treatment of IS children with focal brain lesions. We performed the first reported study using ventriculoscopic laser ablation to treat IS. Seven IS children with drug-resistant epilepsy and definite encephalomalacia on brain magnetic resonance imaging scan were included in this study. Ablation was performed after confirmation of epileptiform discharges by SEEG under the surveillance of ventriculoscope. The median follow-up time for the cohort was 3.1 years and 86% (6/7) of the children had an Engel class ≤III epilepsy at the final follow-up. Five (71%) children had a reduction in seizure medication usage, and the other two were on the same amount as preablation. None of the children experienced serious new neurological deficits. Laser ablation might result in seizure freedom by destroying the local brain network and blocking the spread of abnormal discharges. Intraventricular SEEG and laser ablation was feasible and effective for the treatment of IS. Further studies are warranted.

Clinical Presentation and Management of Hypothalamic Hamartomas: A Systematic Review of the Literature

Abstract Hypothalamic hamartomas (HHs) are composed of abnormally distributed but cytologically normal cellular elements. This disease typically manifests in infancy with gelastic seizures characterized by outbursts of mechanical laughter (mirthless laughter), altered or retained consciousness, refractory to antiepileptic, and later progresses to behavioral and cognitive disturbances and secondary seizure types. A systematic review of the literature on the clinical presentation and management of HHs. A literature search was carried out in electronic databases such as PubMed, COCHRANE, SCOPUS, ScienceDirect, which included the studies reported on “hypothalamic,” “hamartoma,” and “epilepsy,” as well as the outcome with full texts in English. Letters, case reports, reviews, preclinical studies, conference proceedings, protocols, and nonhuman studies were excluded. Duplicates were removed in EndNote X7, and titles and abstracts of all listed articles were scanned. Data analysis of all included studies indicates that smaller lesions result in better outcomes and stereotactic laser ablative procedures have the highest Engel class I outcome percentage. Delalande type II lesions are much more common (n=201) followed by type III (n = 182), IV (n = 71), and I (n = 50). Stereotactic laser ablation is safe for large lesions. HHs can be treated safely when they are small. Therefore, early identification and intervention play a major role. This also prevents the seizure progression, leading to morbidity. SLA has fewer complications and increased seizure-free survival compared to other modalities of treatment.

Overall survival in patients with recurrent glioblastomas with combination chemotherapy and tumor treating fields (TTF).

e14057 Background: Glioblastoma (GBM) is the most common malignant primary brain tumor with an annual incidence of 3.19 per 100,000 and a very poor prognosis. The median overall survival (OS) is 14.6 to 23 months for clinical trial participants and 11 months for the real-world population. Most GBM recurs in 6 to 9 months and the median OS since recurrence is 3 to 9 months. Despite advancements in clinical trials, there is no uniform standard of care (SOC) for recurrent GBM. We investigated a combination therapy of TTF with temozolomide, bevacizumab, and irinotecan (TBI) chemotherapy at GBM recurrence that improves OS of GBM patients with manageable and reversible side effects. Methods: Retrospective review of medical records of adult GBM patients treated at our institution between 2011 and 2021 showed 500 eligible patients. The primary outcomes were OS and SAE. Statistical analyses utilized the Kaplan-Meier estimate and log-rank tests. Data was compared with published GBM studies. Severe adverse events (SAE) were collected and analyzed by the Common Terminology Criteria for Adverse Events Version 5.0. Results: The 500 patients were separated into three groups based on treatment received at GBM recurrence: TBI+TTF (N = 49), TBI (N = 51) and physician’s choice group (PCG) (N = 400). Median age at diagnosis was 60 (range: 18-87). The median OS from diagnosis was 21, 24.5 and 13 months for TBI+TTF, TBI and PCG, respectively. Among the IDH-1 wild type GBM patients, the median OS was 20, 24 and 13 months for TBI+TTF (N = 42), TBI (N = 47), and PCG (N = 352), respectively. Both demonstrated statistically significant differences among the three groups (HR 0.51, 95% CI 0.33-0.78, p = 0.002) (all patients) and (HR 0.54, 95% CI 0.33-0.90, p = 0.017) (IDH-1 wide type GBM). Other contributing factors that may improve OS include a team of brain tumor treating physicians working together for timely identification of GBM at recurrence and implementation of best treatment accordingly, with combination of modalities, such as stereotactic radiosurgery, salvage radiation, laser ablation, or craniotomy followed by chemotherapy and TTF. Among those that were reviewed, the SAE from TBI-TTF, TBI and PCG groups are grade 3 lymphopenia, (51.0% vs 41.2% vs 31.1%), grade 3 hypertension (26.5% vs. 21.6% vs. 13.1%), and grade 3 leukopenia (10.2% vs. 9.8% vs. 13.1%). An updated SAE count and MGMT promoter methylation survival analyses will be presented at the conference. Conclusions: Compared with published results and PCG, the data suggests that both TBI+TTF and TBI regimens increase OS of GBM patients with manageable and reversible side effects. Optimization of GBM treatments through a collaborative teamwork with all surgical, radiation, and chemotherapy modalities may also contribute to the increased OS. Further research of larger sample sizes and prospective clinical trials are warranted to evaluate the two treatment regimens.

Accuracy of robot-assisted stereotactic MRI-guided laser ablation in children with epilepsy.

Robot-assisted (RA) stereotactic MRI-guided laser ablation has been reported to be a safe and effective technique for the treatment of epileptogenic foci in children and adults. In this study the authors aimed to assess the accuracy of RA stereotactic MRI-guided laser fiber placement in children and to identify factors that might increase the risk of misplacement. A retrospective single-institution review of all children from 2019 to 2022 who underwent RA stereotactic MRI-guided laser ablation for epilepsy was undertaken. Placement error was calculated at the target by measuring the Euclidean distance between the implanted laser fiber position and the preoperatively planned position. Collected data included age at surgery, sex, pathology, date of robot calibration, number of catheters, entry position, entry angle, extracranial soft-tissue thickness, bone thickness, and intracranial catheter length. A systematic review of the literature was also performed using Ovid Medline, Ovid Embase, and the Cochrane Central Register of Controlled Trials. In 28 children with epilepsy, the authors assessed 35 RA stereotactic MRI-guided laser ablation fiber placements. Twenty (71.4%) children had undergone ablation for hypothalamic hamartoma, 7 children (25.0%) for presumed insular focal cortical dysplasia, and 1 patient (3.6%) for periventricular nodular heterotopia. Nineteen children were male (67.9.%) and 9 were female (32.1%). The median age at the time of the procedure was 7.67 years (IQR 4.58-12.26 years). The median target point localization error (TPLE) was 1.27 mm (IQR 0.76-1.71 mm). The median offset error between the planned and actual trajectories was 1.04° (IQR 0.73°-1.46°). Patient age, sex, pathology and the time interval between date of surgery and robot calibration, entry position, entry angle, soft-tissue thickness, bone thickness, and intracranial length were not associated with the placement accuracy of the implanted laser fibers. However, the number of catheters placed did correlate with the offset angle error on univariate analysis (ρ = 0.387, p = 0.022). There were no immediate surgical complications. Meta-analysis indicated that the overall pooled mean TPLE was 1.46 mm (95% CI -0.58 to 3.49 mm). RA stereotactic MRI-guided laser ablation for epilepsy in children is highly accurate. These data will aid surgical planning.

865 Survival Benefit of Stereotactic Laser Ablation (SLA) in Newly Diagnosed Glioblastoma Patients: A Matched Cohort Analysis

INTRODUCTION: Post-hoc analysis of a previously published matched cohort study suggests improved survival for glioblastoma patients who underwent stereotactic laser ablation (SLA) relative those who underwent a biopsy, particularly for tumors where contrast enhancing (CE) regions were completely covered by thermal ablation. METHODS: Thirteen patients with newly diagnosed isocitrate dehydrogenase (IDH) wild type glioblastomas (without H3K27 mutation) who underwent SLA with ablation coverage of >90% of the contrast enhancing region were identified. Control cohort was generated by screening patients who underwent stereotactic biopsy for a newly diagnosed tumor matched for: age (+/- 10 years), location, tumor volume (+/- 30% of CE volume), and methyl-guanine methyl-transferase (MGMT promoter methylation status). Post-operative course, complications, 30-day readmission, and overall survival data were collected. RESULTS: The mean KPS for the SLA and biopsy cohorts were comparable (SLA: 90+14; biopsy: 87+16). One patient (8%) in the SLA cohort experienced new-onset diplopia, and one biopsy-only patient (8%) suffered hemi-sensory alteration. There were no 30-day readmissions for either cohort. With a median follow-up of 283 days, the median survival (mOS) for 375 days (∼13 mo) for the SLA treated patient cohort and 264 days (∼ 9 mo) for the biopsy cohort (p = 0.026). To exclude the possibility that this survival difference was due to selection of prognostically favorable patients for SLA, the survival benefit was confirmed by comparison to a second matched biopsy-only glioblastoma cohort from another institution without capacity for SLA. When stratified by MGMT promoter methylation, SLA survival benefit was significant in only patients with methylated tumors (SLA mOS: 620 days (21 mo); biopsy mOS: 171 days (5.7 mo), p = 0.007) CONCLUSIONS: For MGMT promoter methylated glioblastomas, SLA treatment was associated with improved survival relative to biopsy-treated patients. Validation of this finding in a prospective study is warranted.

Magnetic resonance imaging-guided stereotactic laser ablation therapy for the treatment of pediatric epilepsy: a retrospective multiinstitutional study.

The authors of this study evaluated the safety and efficacy of stereotactic laser ablation (SLA) for the treatment of drug-resistant epilepsy (DRE) in children. Seventeen North American centers were enrolled in the study. Data for pediatric patients with DRE who had been treated with SLA between 2008 and 2018 were retrospectively reviewed. A total of 225 patients, mean age 12.8 ± 5.8 years, were identified. Target-of-interest (TOI) locations included extratemporal (44.4%), temporal neocortical (8.4%), mesiotemporal (23.1%), hypothalamic (14.2%), and callosal (9.8%). Visualase and NeuroBlate SLA systems were used in 199 and 26 cases, respectively. Procedure goals included ablation (149 cases), disconnection (63), or both (13). The mean follow-up was 27 ± 20.4 months. Improvement in targeted seizure type (TST) was seen in 179 (84.0%) patients. Engel classification was reported for 167 (74.2%) patients; excluding the palliative cases, 74 (49.7%), 35 (23.5%), 10 (6.7%), and 30 (20.1%) patients had Engel class I, II, III, and IV outcomes, respectively. For patients with a follow-up ≥ 12 months, 25 (51.0%), 18 (36.7%), 3 (6.1%), and 3 (6.1%) had Engel class I, II, III, and IV outcomes, respectively. Patients with a history of pre-SLA surgery related to the TOI, a pathology of malformation of cortical development, and 2+ trajectories per TOI were more likely to experience no improvement in seizure frequency and/or to have an unfavorable outcome. A greater number of smaller thermal lesions was associated with greater improvement in TST. Thirty (13.3%) patients experienced 51 short-term complications including malpositioned catheter (3 cases), intracranial hemorrhage (2), transient neurological deficit (19), permanent neurological deficit (3), symptomatic perilesional edema (6), hydrocephalus (1), CSF leakage (1), wound infection (2), unplanned ICU stay (5), and unplanned 30-day readmission (9). The relative incidence of complications was higher in the hypothalamic target location. Target volume, number of laser trajectories, number or size of thermal lesions, or use of perioperative steroids did not have a significant effect on short-term complications. SLA appears to be an effective and well-tolerated treatment option for children with DRE. Large-volume prospective studies are needed to better understand the indications for treatment and demonstrate the long-term efficacy of SLA in this population.

Stereotactic needle biopsy and laser ablation of geographically distinct lesions through a novel magnetic resonance imaging-compatible cranial stereotaxic frame: illustrative case.

Current technologies that support stereotactic laser ablation (SLA) of geographically distinct lesions require placement of multiple bolts or time-consuming, intertrajectory adjustments. Two geographically distinct nodular lesions were safely biopsied and laser ablated in a 62-year-old woman with recurrent glioblastoma using the ClearPoint Array frame, a novel magnetic resonance imaging-compatible stereotactic frame designed to support independent parallel trajectories without intertrajectory frame adjustment. Here, the authors provide a proof-of-principle case report demonstrating that geographically distinct lesions can be safely biopsied and ablated through parallel trajectories supported by the ClearPoint Array frame without intertrajectory adjustment.

Stereotactic laser ablation in neuro-oncology - A survey among European neurosurgeons

IntroductionIn the last decades, the application of stereotactic laser ablation (SLA) for the treatment of intracranial tumours has been growing, even though comparative trials are lacking. Our aim was to investigate the familiarity with SLA of neurosurgeons in Europe and their opinion regarding potential neuro-oncological indications. Furthermore, we investigated treatment preferences and variability for three exemplar neuro-oncological cases and willingness to refer for SLA. Material and methodsA 26-questions survey was mailed to members of the EANS neuro-oncology section. We presented three clinical cases of respectively deep-seated glioblastoma, recurrent metastasis and recurrent glioblastoma. Descriptive statistics was applied to report results. Results110 respondents completed all questions. Recurrent glioblastoma and recurrent metastases were regarded as the most feasible indications for SLA (chosen by 69% and 58% of the respondents) followed by newly diagnosed high-grade gliomas (31%). Seventy percent of respondents would refer patients for SLA. The majority of respondents would consider SLA as a treatment option for all three presented cases: 79% for the deep-seated glioblastoma case, 65% for the recurrent metastasis case and 76% for the recurrent glioblastoma case. Among respondents who wouldn't consider SLA, preference for standard treatment and lack of clinical evidence were reported as the main reasons. ConclusionsMost of respondents considered SLA as a treatment option for recurrent glioblastoma, recurrent metastases and newly diagnosed deep-seated glioblastoma. At the moment the current evidence to support such a treatment is very low. Comparative prospective trials are needed to support the use of SLA and determine proper indications.

Letter to the Editor Regarding “Stereotactic biopsy and laser ablation of the ganglioglioma using a thulium laser: a video case report”

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Stereotactic biopsy and laser ablation of the ganglioglioma using a thulium laser: a video case report

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Decision-making in stereotactic epilepsy surgery.

Surgery can cure or significantly improve both the frequency and the intensity of seizures in patients with medication-refractory epilepsy. The set of diagnostic and therapeutic interventions involved in the path from initial consultation to definitive surgery is complex and includes a multidisciplinary team of neurologists, neurosurgeons, neuroradiologists, and neuropsychologists, supported by a very large epilepsy-dedicated clinical architecture. In recent years, new practices and technologies have emerged that dramatically expand the scope of interventions performed. Stereoelectroencephalography has become widely adopted for seizure localization; stereotactic laser ablation has enabled more focal, less invasive, and less destructive interventions; and new brain stimulation devices have unlocked treatment of eloquent foci and multifocal onset etiologies. This article articulates and illustrates the full framework for how epilepsy patients are considered for surgical intervention, with particular attention given to stereotactic approaches.

345 Comparable Safety Profile Between Laser Interstitial Thermal Therapy (LITT) and Stereotactic Needle Biopsy in 30-Day and 90-Day Readmission: A National Readmissions Database Analysis

INTRODUCTION: The procedural elements of Laser Interstitial Thermal Therapy (LITT, also known as stereotactic laser ablation (SLA)) and stereotactic needle biopsy are highly similar. METHODS: We queried the National Readmission Database (NRD, 2010-18) for patients who underwent elective LITT or biopsy using International Classification of Diseases 9th and 10th edition codes. Readmission was defined planned, related admissions following the index admission. Odds of 30- and 90-days readmission were calculated using multivariable logistic regression. RESULTS: 305 LITT and 7,419 needle biopsy treated brain tumor were identified. The LITT treated patients were younger (p < 0.001), female (p=0.008), and insured privately (compared to Medicare or Medicaid, p < 0.001). In terms of cancer type, a greater proportion of LITT cohort were patients brain metastasis (relative to primary brain cancer, 38.7% vs 7.2%, p < 0.001). There was no difference in non-routine discharge (LITT: 73.8%, n = 225 discharged to home vs biopsy: 80 %, n = 5,392, p = 0.826) or in-hospital mortality (0.3%,n=1 vs 0.7%, n = 50, p = 0.715). The most common neurosurgical reasons for readmissions at 30-days included unplanned readmission for index diagnosis (LITT: 2%, n = 7 vs biopsy: 3.7%, n = 272), infection (0.6%, n = 2 vs 0.46%, n = 34), seizure (0.3%, n = 1 vs 0.74%, n = 54) and cerebrovascular complication (0.3%, n = 1 vs 1%, n = 55) . The most common reason for non-neurosurgical readmission at 30 days for biopsy treated patients was deep vein thrombosis (DVT) / pulmonary embolism (PE) (0.46%, n = 35) and for LITT treated patients was an electrolyte abnormality (0.6%, n = 2). In both univariate and multivariable analyses, the odds of 30- and 90-days overall readmission, as well as neurosurgical and non-neurosurgical readmission were comparable between LITT and biopsy. CONCLUSION: The NRD analysis of 30- and 90-day readmission suggest comparable safety profile between LITT and stereotactic needle biopsy as treatment for brain tumor patients.

Initial Clinical Experience With ClearPoint SmartFrame Array–Aided Stereotactic Procedures

The ClearPoint SmartFrame Array (ClearPoint Neuro, Inc., Solana Beach, CA) system consists of a magnetic resonance imaging compatible frame supported by a customized neuro navigation software. This system received U.S. Food and Drug Administrationclearance for clinical use in January 2021. Our objective was to report initial safety data and user experience of SmartFrame Array-supported stereotactic procedures. We prospectively followed the first 10 consecutive patients who underwent stereotactic procedures supported by SmartFrame Array. Clinical and procedural data were recorded and compared to data obtained from prior cases with SmartFrame XG. Ten patients underwent stereotactic needle biopsy, stereotactic laser ablation (SLA), or combined biopsy/SLA procedures. For needle biopsies (n= 9), the average maximal diameter of the contrast-enhancing target lesion was 9.9 ± 2.8 mm. The radial error of stereotaxis was less than 2 mm. Definitive diagnosis was achieved in all cases. For procedures involving SLA (n= 5), 100% of the contrast-enhancing lesion was ablated. All patients were discharged home by postoperative day 2. There were no 30-day readmissions, morbidity, or mortality. The average stereotaxis time for the SmartFrame Array-aided single trajectory procedure was 80 ± 9.5 minutes, which compared favorably to that required for the earlier generation SmartFrame XG frame (111.5 ± 16.5 minutes; P < 0.01). The unique Array design supported stereotactic procedures that cannot be easily achieved with the previous SmartFrame XG frame. The SmartFrame Array system offers a more rigid and compact build to enhance procedural efficiency while maintaining accuracy and safety. The design supports multi-trajectory stereotaxis, allowing novel clinical applications.

Stealth Autoguide for robotic-assisted laser ablation for lesional epilepsy: illustrative case

BACKGROUNDLaser interstitial thermal therapy has been used in tumor and epilepsy surgery to maximize clinical treatment impact while minimizing morbidity. This intervention places a premium on accuracy. With the advent of robotics, neurosurgery is entering a new age of improved accuracy. Here, the authors described the use of robotic-assisted laser placement for the treatment of epileptiform lesions.OBSERVATIONSThe authors presented a case of a 21-year-old woman with medically intractable epilepsy, localized to left mesial temporal sclerosis and left temporal encephalocele by way of stereotactic electroencephalography, who presented for consideration of surgical intervention. When presented with resection versus laser ablation, the patient opted for laser ablation. The patient received robotic-assisted stereotactic laser ablation (RASLA) using a Stealth Autoguide. The patient was seizure free (10 weeks) after surgical ablation.LESSONSRASLA is an effective way to treat epilepsy. Here, the authors reported the first RASLA procedure with a Stealth Autoguide to treat epilepsy. The procedure can be performed effectively and efficiently for multiple epileptic foci without the need for bulkier robotic options or head frames that may interfere with the use of magnetic resonance imaging for heat mapping.

Stereotactic Laser Ablation (SLA) followed by consolidation stereotactic radiosurgery (cSRS) as treatment for brain metastasis that recurred locally after initial radiosurgery (BMRS): a multi-institutional experience.

The optimal treatment paradigm for brain metastasis that recurs locally after initial radiosurgery remains an area of active investigation. Here, we report outcomes for patients with BMRS treated with stereotactic laser ablation (SLA, also known as laser interstitial thermal therapy, LITT) followed by consolidation radiosurgery. Clinical outcomes of 20 patients with 21 histologically confirmed BMRS treated with SLA followed by consolidation SRS and > 6months follow-up were collected retrospectively across three participating institutions. Consolidation SRS (5Gy × 5 or 6Gy × 5) was carried out 16-73days (median of 26days) post-SLA in patients with BMRS. There were no new neurological deficits after SLA/cSRS. While 3/21 (14.3%) patients suffered temporary Karnofsky Performance Score (KPS) decline after SLA, no KPS decline was observed after cSRS. There were no 30-day mortalities or wound complications. Two patients required re-admission within 30days of cSRS (severe headache that resolved with steroid therapy (n = 1) and new onset seizure (n = 1)). With a median follow-up of 228days (range: 178-1367days), the local control rate at 6 and 12months (LC6, LC12) was 100%. All showed diminished FLAIR volume surrounding the SLA/cSRS treated BMRS at the six-month follow-up; none of the patients required steroid for symptoms attributable to these BMRS. These results compare favorably to the available literature for repeat SRS or SLA-only treatment of BMRS. This multi-institutional experience supports further investigations of SLA/cSRS as a treatment strategy for BMRS.

RADT-04. STEREOTACTIC LASER ABLATION (SLA) FOLLOWED BY CONSOLIDATION STEREOTACTIC RADIOSURGERY (SRS) AS A TREATMENT STRATEGY FOR BRAIN METASTASIS THAT RECURRED LOCALLY AFTER INITIAL RADIOSURGERY (BMRS)

Abstract INTRODUCTION In independent clinical trials, ~30% of brain metastases recur locally after radiosurgery (BMRS). For these lesions, treatment with stereotactic laser ablation (SLA, also known as laser interstitial thermal therapy (LITT)) alone achieves a 12-month local control (LC12) of 54-85% while repeat SRS achieved LC12 of 54-79%. Here, we report favorable outcomes for BMRS treated with SLA followed by consolidation radiosurgery (SLA/cSRS). METHODS Clinical outcome of 18 patients with 19 histologically confirmed BMRS treated with SLA followed by consolidation SRS and &amp;gt;3 months follow-up were collected retrospectively across three institutions. Local control was defined as stability or decrease in contrast-enhancing (CE) and FLAIR volume. RESULTS SLA achieved ablation of 73-100% of the BMRS CE volumes. Consolidation hypo-fractionated radiosurgery (5 Gy x 5 or 6 Gy x 5) was carried out 16-40 days post-SLA (median of 26 days). With a median follow-up of 185 days (range: 93-1367 days) and median overall survival (OS) of 185 days (range: 99-1367 days), 100% LC12 was achieved. 13/18 (72%) patients that required steroid therapy prior to SLA/cSRS were successfully weaned off steroid by three months post-SLA/cSRS. Post-SLA, KPS declined for 3/19 (16%) patients and improved for 1/19 (5%) patients. No KPS changes occurred subsequent to consolidation SRS. There were no 30-day mortalities or wound complications. Two patients required re-admission within 30 days of SRS (severe headache that resolved with steroid therapy (n=1) and new-onset seizure (n=1)). Except for two patients who suffered histologically confirmed, local failure at 649 and 899 days, all other patients are either alive (n=6) or died from systemic disease progression (n=10). None of the treated patients developed symptomatic radiation necrosis. CONCLUSIONS This collaborative institutional experience support efficacy and safety of SLA followed by consolidation SRS as a treatment for BMRS. The treatment strategy warrants further investigations.

A-68 Neuropsychological Predictors of Seizure Freedom in Patients Undergoing Stereotactic Laser Ablation of the Hippocampus (SLAH) for Refractory Epilepsy

Abstract Objective Presurgical cognitive and psychiatric status can serve as predictors of surgical outcomes; however, there are no studies that assess the predictive nature of cognitive factors and psychiatric illness on seizure freedom following stereotactic laser ablation, a novel, minimally invasive surgical approach, of the hippocampus (SLAH). Therefore, this study aimed to assess whether neuropsychological factors were associated with long-term postoperative outcome, defined as time maintaining continuous postoperative seizure freedom (Engel Class I outcome persistently after surgery), after mesial temporal laser ablation surgery. Method Forty-one patients (Age M = 37.5 ± 12.6; 61% female; 63% left mesial temporal ablation; 37% right mesial temporal ablation) were selected from retrospective data collection of epilepsy surgery outcomes following mesial temporal laser ablation. Patients were assessed with a presurgical neuropsychological battery as part of Phase I work-up. Results Wilcoxon rank-sum tests revealed there were no significant differences between groups (seizure free and non-seizure free) across presurgical intellectual functioning, (seizure free M = 37.6; non-seizure free M = 40.6; p = 0.31), verbal memory (p = 0.59), visual memory (p = 0.39), and language composite scores (p = 0.87). There was also no significant difference in presurgical mean depression scores (p = 0.81). Conclusions There were no significant differences between groups in presurgical cognitive and psychiatric predictors on seizure outcomes; however, sample size is a limitation. Further investigations are needed given that cognitive and psychiatric predictors may be associated with SLAH outcomes. Additionally, these findings add to the absence of literature on cognitive and psychiatric predictors in SLAH.