Stereotactic laser therapy in cerebral gliomas

A Systematic Review Informing the Management of Symptomatic Brain Radiation Necrosis After Stereotactic Radiosurgery and International Stereotactic Radiosurgery Society Recommendations

Radiation necrosis (RN) secondary to stereotactic radiosurgery is a significant cause of morbidity. The optimal management of corticosteroid-refractory brain RN remains unclear. Our objective was to summarize the literature specific to efficacy and toxicity of treatment paradigms for patients with symptomatic corticosteroid-refractory RN and to provide consensus guidelines for grading and management of RN on behalf of the International Stereotactic Radiosurgery Society. A systematic review of articles pertaining to treatment of RN with bevacizumab, laser interstitial thermal therapy (LITT), surgical resection, or hyperbaric oxygen therapy was performed. The primary composite outcome was clinical and/or radiologic stability/improvement (ie, proportion of patients achieving improvement or stability with the given intervention). Proportions of patients achieving the primary outcome were pooled using random weighted-effects analysis but not directly compared between interventions. Twenty-one articles were included, of which only 2 were prospective studies. Thirteen reports were relevant for bevacizumab, 5 for LITT, 5 for surgical resection and 1 for hyperbaric oxygen therapy. Weighted effects analysis revealed that bevacizumab had a pooled symptom improvement/stability rate of 86% (95% CI 77%-92%), pooled T2 imaging improvement/stability rate of 93% (95% CI 87%-98%), and pooled T1 postcontrast improvement/stability rate of 94% (95% CI 87%-98%). Subgroup analysis showed a statistically significant improvement favoring treatment with low-dose (below median, ≤7.5 mg/kg every 3 weeks) versus high-dose bevacizumab with regards to symptom improvement/stability rate (P = .02) but not for radiologic T1 or T2 changes. The pooled T1 postcontrast improvement/stability rate for LITT was 88% (95% CI 82%-93%), and pooled symptom improvement/stability rate for surgery was 89% (95% CI 81%-96%). Toxicity was inconsistently reported but was generally low for all treatment paradigms. Corticosteroid-refractory RN that does not require urgent surgical intervention, with sufficient noninvasive diagnostic testing that favors RN, can be treated medically with bevacizumab in carefully selected patients as a strong recommendation. The role of LITT is evolving as a less invasive image guided surgical modality; however, the overall evidence for each modality is of low quality. Prospective head-to-head comparisons are needed to evaluate the relative efficacy and toxicity profile among treatment approaches.

Laser interstitial thermal therapy for the treatment of insular lesions: A systematic review

Background

The surgical treatment of insular lesions has been historically associated with high morbidity. Laser interstitial thermal therapy (LITT) has been increasingly used in the treatment of insular lesions, commonly neoplastic or epileptogenic. Stereotaxis is used to guide laser probes to the insula where real-time magnetic resonance thermometry defines lesion creation. There is an absence of previously published reviews on insular LITT, despite a rapid uptake in use, making further study imperative.

Methods

Here we present a systematic review of the PubMed and Scopus databases, examining the reported clinical indications, outcomes, and adverse effects of insular LITT.

Results

A review of the literature revealed 10 retrospective studies reporting on 53 patients (43 pediatric and 10 adults) that were treated with insular LITT. 87% of cases were for the treatment of epilepsy, with 89% of patients achieving seizure outcomes of Engle I-III following treatment. The other 13% of cases reported on insular tumors and radiological improvement was seen in all cases following treatment. All but one study reported adverse events following LITT with a rate of 37%. The most common adverse events were transient hemiparesis (29%) and transient aphasia (6%). One patient experienced an intracerebral hemorrhage, which required a decompressive hemicraniectomy, with subsequent full recovery.

Conclusion

This systematic review highlights the suitability of LITT for the treatment of both insular seizure foci and insular tumors. Despite the growing use of this technique, prospective studies remain absent in the literature. Future work should directly evaluate the efficacy of LITT with randomized and controlled trials.

Laser hyperthermia: Past, present, and future

Magnetic resonance imaging-guided laser interstitial thermal therapy (LITT) is an ablative procedure using heat from a laser to provide cytoreduction in tissue. It is a minimally invasive procedure that has been used in intracranial pathologies such as high-grade gliomas, metastatic lesions, epilepsy, and other lesions. While LITT may offer a more acceptable complication profile compared to open surgery, the role of laser therapy for intracranial lesions in current treatment paradigms continues to evolve. This review will focus on the background and application of LITT, the current evidence for its use, and future directions for the technology.

Laser thermal therapy in the management of high-grade gliomas

Laser interstitial thermal therapy (LITT) is a minimally invasive therapy that have been used for brain tumors, epilepsy, chronic pain, and other spine pathologies. This therapy is performed under imaging and stereotactic guidance to precisely direct the probe and ablate the area of interest using real-time magnetic resonance (MR) thermography. LITT has gained popularity as a treatment for glioma because of its minimally invasive nature, small skin incision, repeatability, shorter hospital stay, and the possibility of receiving adjuvant therapy shortly after surgery instead of several weeks as required after open surgical resection. Several reports have demonstrated the usefulness of LITT in the treatment of newly-diagnosed and recurrent gliomas. In this review, we will summarize the recent evidence of this therapy in the field of glioma surgery and the future perspectives of the use of LITT combined with other treatment strategies for this devastating disease.

Laser Interstitial Thermal Therapy for Glioblastoma: A Single-Center Experience

BACKGROUND

Surgical resection has been shown to prolong survival in patients with glioblastoma multiforme (GBM), although this benefit has not been demonstrated for reoperation following tumor recurrence. Laser interstitial thermal therapy (LITT) is a minimally invasive ablation technique that has been shown to effectively reduce tumor burden in some patients with intracranial malignancy. The aim of this study was to describe the safety and efficacy of LITT for recurrent and newly diagnosed GBM at a large tertiary referral center.

METHODS

Patients with GBM receiving LITT were retrospectively analyzed. Overall survival from the time of LITT was the primary end point measured.

RESULTS

There were 69 patients identified for inclusion in this study. The median age of the cohort was 56 years (range, 15-77 years). Median tumor volume was 10.4 cm³ (range, 1.0-64.0 cm³). A Kaplan-Meier estimate of median overall survival for the series from the time of LITT was 12 months (95% confidence interval 8-16 months). Median progression-free survival for the cohort from LITT was 4 months (95% confidence interval 3-7 months). Adjuvant chemotherapy significantly prolonged progression-free survival and overall survival (P < 0.01 for both) in the cohort. Gross total ablation was not significantly associated with progression-free survival (P = 0.09).

CONCLUSIONS

LITT can safely reduce intracranial tumor burden in patients with GBM who have exhausted other adjuvant therapies or are poor candidates for conventional resection techniques.

Current Role of Laser Interstitial Thermal Therapy in the Treatment of Intracranial Tumors

Laser interstitial thermal therapy (LITT) is gaining popularity in the treatment of both primary and secondary intracranial tumors. The goal of LITT is to deliver thermal energy in a predictable, controlled, and minimally invasive fashion. It can be particularly valuable in patients with recurrent tumors who, due to previous radiation or surgery, may have a potentially higher risk of wound breakdown or infection with repeat craniotomy. Deep-seated lesions that are often inaccessible through open approaches (thalamus, hypothalamus, mesial basal temporal lobe, brainstem) may also be suitable targets. The experience and data published thus far on this modality is limited but growing. This review highlights the use of LITT as a primary treatment method in a variety of intracranial tumors, as well as its application as an adjunct to established surgical techniques.

Epilepsy surgery in tuberous sclerosis complex (TSC): emerging techniques and redefinition of treatment goals

Epilepsy occurs in nearly all patients with tuberous sclerosis and is often refractory to medical treatment. The definition of surgical candidacy in these patients has broadened in recent years due to philosophical and technological advances. The goals of surgery have shifted to focusing on quality of life and maximizing neurodevelopmental potential in patients unable to obtain seizure freedom. Novel diagnostic, ablative, and neuromodulatory techniques have been developed that may help patients that were previously considered inoperable to have an improved quality of life. In the coming years, it is expected that these techniques will be further refined and lead to an improvement of neurological prognosis in patients with tuberous sclerosis.

In situ vaccination with laser interstitial thermal therapy augments immunotherapy in malignant gliomas

INTRODUCTION

Laser interstitial thermal therapy (LITT) remains a promising advance in the treatment of primary central nervous system malignancies. As indications for its use continue to expand, there has been growing interest in its ability to induce prolonged blood brain barrier (BBB) permeability through hyperthermia, potentially increasing the effectiveness of current therapeutics including BBB-impermeant agents and immunotherapy platforms.

METHODS

In this review, we highlight the mechanism of hyperthermic BBB disruption and LITT-induced immunogenic cell death in preclinical models and humans. Additionally, we summarize ongoing clinical trials evaluating a combination approach of LITT and immunotherapy, which will likely serve as the basis for future neuro-oncologic treatment paradigms.

RESULTS

There is evidence to suggest a highly immunogenic response to laser interstitial thermal therapy through activation of both the innate and adaptive immune response. These mechanisms have been shown to potentiate standard methods of oncologic care. There are only a limited number of clinical trials are ongoing to evaluate the utility of LITT in combination with immunotherapy.

CONCLUSION

LITT continues to be studied as a possible technique to bridge the gap between exciting preclinical results and the limited successes seen in the field of neuro-oncology. Preliminary data suggests a substantial benefit for use of LITT as a combination therapy in several clinical trials. Further investigation is required to determine whether or not this treatment paradigm can translate into long-term durable results for primary intracranial malignancies.

The intersection between immunotherapy and laser interstitial thermal therapy: a multipronged future of neuro-oncology

The rise of immunotherapy (IT) in oncological treatment has greatly improved outcomes in a number of disease states. However, its use in tumors of the central nervous system (CNS) remains limited for multiple reasons related to the unique immunologic tumor microenvironment. As such, it is valuable to consider the intersection of IT with additional treatment methods that may improve access to the CNS and effectiveness of existing IT modalities. One such combination is the pairing of IT with localized hyperthermia (HT) generated through technologies such as laser interstitial thermal therapy (LITT). The wide-ranging immunomodulatory effects of localized and whole-body HT have been investigated for some time. Hyperthermia has demonstrated immunostimulatory effects at the level of tumor cells, immune cells, and the broader environment governing potential immune surveillance. A thorough understanding of these effects as well as the current and upcoming investigations of such in combination with IT is important in considering the future directions of neuro-oncology.

Laser Interstitial Thermal Therapy in the treatment of brain metastases and radiation necrosis

Stereotactic Radiosurgery has become the main treatment for patients with limited number of brain metastases (BM). Recently, with the increasing use of this modality, there is a growth in recurrence cases. Recurrence after radiation therapy can be divided in changes favoring either tumor recurrence or radiation necrosis (RN). Laser Interstitial Thermal Therapy (LITT) is minimally invasive treatment modality that has been used to treat primary and metastatic brain tumors. When associated with real-time thermometry using Magnetic Resonance Imaging, the extent of ablation can be controlled to provide maximum coverage and avoid eloquent areas. The objective of this study was to investigate the use of LITT in the treatment of BM. An extensive review of the relevant literature was conducted and the outcome results are discussed. There is an emphasis on safety and local control rate of patients treated with this modality. The findings of our study suggest that LITT is a viable safe technique to treat recurrent BM, especially in patients with deep-seated lesions where surgical resection is not an option.

Lessons Learned in Using Laser Interstitial Thermal Therapy for Treatment of Brain Tumors: A Case Series of 238 Patients from a Single Institution

BACKGROUND

Laser interstitial thermal therapy (LITT) is a novel, minimally invasive alternative to craniotomy, and as with any new technology, comes with a learning curve.

OBJECTIVE

We present our experience detailing the evolution of this technology in our practice in one of the largest patient cohorts to date regarding LITT in neuro-oncology.

METHODS

We reviewed 238 consecutive patients with brain tumor treated with LITT at our institution. Data on patient, surgery and tumor characteristics, and follow-up were collected. Patients were categorized into 2 cohorts: early (<2014, 100 patients) and recent (>2015, 138 patients). Median follow-up for the entire cohort was 8.4 months.

RESULTS

The indications for LITT included gliomas (70.2%), radiation necrosis (21.0%), and metastasis (8.8%). Patient demographics stayed consistent between the 2 cohorts, with the exception of age (early, 54.3; recent, 58.4; P = 0.04). Operative time (6.6 vs. 3.5; P < 0.001) and number of trajectories (53.1% vs. 77.9% with 1 trajectory; P < 0.001) also decreased in the recent cohort. There was a significant decrease in permanent motor deficits over time (15.5 vs. 4.4%; P = 0.005) and 30-day mortality (4.1% vs. 1.5%) also decreased (not statistically significant) in the recent cohort. In terms of clinical outcomes, poor preoperative Karnofsky Performance Status (≤70) were significantly correlated with increased permanent deficits (P = 0.001) and decreased overall survival (P < 0.001 for all time points).

CONCLUSIONS

We observed improvement in operative efficiency and permanent deficits over time and also patients with poor preoperative Karnofsky Performance Status achieved suboptimal outcomes with LITT. As many other treatment modalities, patient selection is important in this procedure.

Upfront Magnetic Resonance Imaging-Guided Stereotactic Laser-Ablation in Newly Diagnosed Glioblastoma: A Multicenter Review of Survival Outcomes Compared to a Matched Cohort of Biopsy-Only Patients

BACKGROUND

Laser ablation (LA) is used as an upfront treatment in patients with deep seated newly diagnosed Glioblastoma (nGBM).

OBJECTIVE

To evaluate the outcomes of LA in patients with nGBM and compare them with a matched biopsy-only cohort.

METHODS

Twenty-four nGBM patients underwent upfront LA at Cleveland clinic, Washington University in St. Louis, and Yale University (6/2011-12/2014) followed by chemo/radiotherapy. Also, 24 out of 171 nGBM patients with biopsy followed by chemo/radiotherapy were matched based on age (< 70 vs ≥ 70), gender, tumor location (deep vs lobar), and volume (<11 cc vs ≥11 cc). Progression-free survival (PFS), overall survival (OS), and disease-specific PFS and OS were outcome measures. Three prognostic groups were identified based on extent of tumor ablation by thermal-damage-threshold (TDT)-lines.

RESULTS

The median tumor volume in LA (n = 24) and biopsy only (n = 24) groups was 9.3 cm3 and 8.2 cm3 respectively. Overall, median estimate of OS and PFS in LA cohort was 14.4 and 4.3 mo compared to 15.8 mo and 5.9 mo for biopsy only cohort. On multivariate analysis, favorable TDT-line prognostic groups were associated with lower incidence of disease specific death (P = .03) and progression (P = .05) compared to other groups including biopsy only cohort. Only age (<70 yr, P = .02) and tumor volume (<11 cc, P = .03) were favorable prognostic factors for OS.

CONCLUSION

The maximum tumor coverage by LA followed by radiation/chemotherapy is an effective treatment modality in patients with nGBM, compared to biopsy only cohort. The TDT-line prognostic groups were independent predictor of disease specific death and progression after LA.

Laser interstitial thermal therapy in gliomas

Laser interstitial thermal therapy (LITT) has been used for brain metastasis, epilepsy, and necrosis, as well as gliomas as a minimally invasive treatment for many years. With the improvement of the thermal monitoring and ablation precision, especially the application of magnetic resonance (MR) thermography in the procedure and the available two commercial laser systems nowadays, LITT is gradually accepted by more neurosurgical centers. Recently, some new concepts, for example the adjuvant chemotherapy or radiation following LITT, the combination of immunotherapy and LITT regarding the glioma treatment are proposed and currently being investigated. The aim of this study is to summarize the evolution of LITT especially for brain gliomas and a possible outlook of the future.

Recent technological advancements in thermometry

Thermometry is the key factor for achieving successful thermal therapy. Although invasive thermometry with a probe has been used for more than four decades, this method can only detect the local temperature within the probing volume. Noninvasive temperature imaging using a tomographic technique is ideal for monitoring hot-spot formation in the human body. Among various techniques, such as X-ray computed tomography, microwave tomography, echo sonography, and magnetic resonance (MR) imaging, the proton resonance frequency shift method of MR thermometry is the only method currently available for clinical practice because its temperature sensitivity is consistent in most aqueous tissues and can be easily observed using common clinical scanners. New techniques are being proposed to improve the robustness of this method against tissue motion. MR techniques for fat thermometry were also developed based on relaxation times. One of the latest non-MR techniques to attract attention is photoacoustic imaging.

Ablation dynamics of subsequent thermal doses delivered to previously heat-damaged tissue during magnetic resonance-guided laser-induced thermal therapy

OBJECTIVE

Intraoperative dynamics of magnetic resonance-guided laser-induced thermal therapy (MRgLITT) have been previously characterized for ablations of naive tissue. However, most treatment sessions require the delivery of multiple doses, and little is known about the ablation dynamics when additional doses are applied to heat-damaged tissue. This study investigated the differences in ablation dynamics between naive versus damaged tissue.

METHODS

The authors examined 168 ablations from 60 patients across various surgical indications. All ablations were performed using the Visualase MRI-guided laser ablation system (Medtronic), which employs a 980-nm diffusing tip diode laser. Cases with multiple topographically overlapping doses with constant power were selected for this study. Single-dose intraoperative thermal damage was used to calculate ablation rate based on the thermal damage estimate (TDE) of the maximum area of ablation achieved (TDEmax) and the total duration of ablation (tmax). We compared ablation rates of naive undamaged tissue and damaged tissue exposed to subsequent thermal doses following an initial ablation.

RESULTS

TDEmax was significantly decreased in subsequent ablations compared to the preceding ablation (initial ablation 227.8 ± 17.7 mm2, second ablation 164.1 ± 21.5 mm2, third ablation 124.3 ± 11.2 mm2; p = < 0.001). The ablation rate of subsequent thermal doses delivered to previously damaged tissue was significantly decreased compared to the ablation rate of naive tissue (initial ablation 2.703 mm2/sec; second ablation 1.559 mm2/sec; third ablation 1.237 mm2/sec; fourth ablation 1.076 mm/sec; p = < 0.001). A negative correlation was found between TDEmax and percentage of overlap in a subsequent ablation with previously damaged tissue (r = -0.164; p < 0.02).

CONCLUSIONS

Ablation of previously ablated tissue results in a reduced ablation rate and reduced TDEmax. Additionally, each successive thermal dose in a series of sequential ablations results in a decreased ablation rate relative to that of the preceding ablation. In the absence of a change in power, operators should anticipate a possible reduction in TDE when ablating partially damaged tissue for a similar amount of time compared to the preceding ablation.

Laser Ablation Therapy for Pediatric Patients with Intracranial Lesions in Eloquent Areas

BACKGROUND

Laser interstitial thermal therapy (LITT) is an alternative, less-invasive, and, in some circumstances, effective treatment for patients with intracranial pathology including epilepsy and some tumors. For intracranial lesions in eloquent areas, resection by conventional craniotomy proves often to be a challenge, including in the care of pediatric patients. Herein, we reviewed our experience with magnetic resonance imaging (MRI)-guided LITT as treatment for pediatric patients with intracranial lesions in eloquent areas and evaluate neurologic function and clinical outcomes.

METHODS

We retrospectively reviewed consecutive patients with intracranial lesions in eloquent speech and motor areas who underwent MRI-guided LITT. Clinical evaluation, including neurologic function and neuropsychological testing, was conducted according to clinical considerations. MRI pre- and postoperative imaging was reviewed to compare the change of lesion size.

RESULTS

Five pediatric patients received MRI-guided LITT of intracranial lesions in eloquent cortex. One patient experienced complications secondary to MRI-guided LITT, but neither was discharged with a neurologic deficit.

CONCLUSIONS

For intracranial lesions in the eloquent cortex, conventional craniotomy with surgical resection is a challenge for neurosurgeons, especially pediatric patients. MRI-guided LITT provides a less-invasive and potentially effective option for treatment in the management of pediatric epilepsy and tumors.

Surgical Considerations in the Optimal Management of Patients with Malignant Brain Tumors

OPINION STATEMENT

Advances in technology are revolutionizing medicine and the limits of what we can offer to our patients. In neurosurgery, technology continues to reduce morbidity, increase surgical accuracy, facilitate tissue acquisition, and promote novel techniques for prolonging survival in patients with neuro-oncologic disease. Surgery has been the backbone of glioma diagnosis and treatment by providing adequate, high quality material for precise histologic diagnosis, and genomic characterization in the setting of significant intratumoral heterogeneity, thus allowing personalized treatment selection in the clinic. The ability to obtain and accurately measure the maximal extent of resection in glioma surgery also remains a central role of the neurosurgeon in managing this cancer. To meet these goals, today's operating room has transformed from the traditional operating table and anesthesia machine to include neuronavigation instrumentation, intraoperative computed tomography, and magnetic resonance imaging scanners, advanced surgical microscopes fitted with fluorescent light filters, and electrocorticography machines. While surgeons, oncologists, and radiation oncologists all play unique critical roles in the care of patients with malignant gliomas, familiarity with developing techniques in complimentary subspecialties can enhance coordination of patient care, research productivity, professional interactions, and patient confidence and comfort with the physician team. Herein, we provide a summary of the advances in the field of neurosurgical oncology which allow more precise and optimal surgical resection for patients with malignant gliomas.

Laser-Induced Thermal Therapy in Neuro-Oncology: A Review

OBJECTIVES

Laser therapy has become an appealing treatment modality in neurosurgery. In this review, we report on the history, physics, surgical steps, indications and uses, and complications that have been reported to date.

METHODS

An extensive literature search was performed for laser interstitial thermal therapy (LITT) and laser therapy in the context of glial tumors, metastatic lesions, pediatric brain tumors, and radiation necrosis. Reported complications in each series also were reviewed.

RESULTS

In the past decade, multiple studies have demonstrated the use, outcomes, and complications associated with LITT in neurosurgery. These same studies have consistently reported an overall benefit of LITT in cases in which traditional surgical approaches may be limited by the patient's clinical status, tumor location, or overall prognosis. However, there have been complications reported from local effects of thermal damage, technical error, and edema development. Increased experience has reduced complications and brought more promising results.

CONCLUSIONS

With the advent of real-time monitoring and damage estimation, LITT has gained ground in the management of intracranial tumors. Larger scale trials must be performed to develop standard protocols to define specific indications for use. Further large clinical studies for LITT in non-oncologic cases are also of interest.

Quantitative Volumetric Analysis Following Magnetic Resonance-Guided Laser Interstitial Thermal Ablation of Cerebellar Metastases

BACKGROUND

Treating recurrent posterior fossa metastases after previous radiation therapy and surgical resection remains challenging. Magnetic resonance laser-induced thermal therapy (MR-LITT) is a promising treatment for recurrent lesions, but data on safety, efficacy, and postablation volume change in the posterior fossa are lacking.

METHODS

All patients with recurrent posterior fossa metastatic lesions treated with MR-LITT by the senior neurosurgeon were included in the study. Preoperative and postoperative follow-up magnetic resonance imaging (MRI) studies were used to measure lesional and perilesional edema volume. These measurements were compared to calculate percent ablation volume. All patients' clinical examinations were followed closely.

RESULTS

Four patients with recurrent cerebellar metastases were treated with MR-LITT. The average percent lesion ablated was 97.1% (range, 88.2%-100%). The average preoperative lesion volume was 3.3 cm³ (range, 1.1-7.2 cm³), and the average final postoperative volume was 3.8 cm³ (range, 0.5-7.6 cm³). Lesion volume increased to maximum volume on postoperative day 1, with an average increase of 486.9%. The extrapolated average time for the lesion to shrink to below the initial size was 294.5 days. There was a trend toward a decrease in average edema volume from the preoperative MRI of 17.8 cm³ to final postoperative follow-up MRI of 3.4 cm³ (P = 0.0952). No postoperative hydrocephalus or complications occurred.

CONCLUSIONS

This pilot study shows that LITT appears to be a safe and promising treatment for recurrent posterior fossa metastatic lesions up to 7.2 cm³. Further randomized controlled studies are warranted to further characterize the long-term efficacy of this therapy.

Stereotactic Laser Interstitial Thermal Therapy for Recurrent High-Grade Gliomas

BACKGROUND

The value of maximal safe cytoreductive surgery in recurrent high-grade gliomas (HGGs) is gaining wider acceptance. However, patients may harbor recurrent tumors that may be difficult to access with open surgery. Laser interstitial thermal therapy (LITT) is emerging as a technique for treating a variety of brain pathologies, including primary and metastatic tumors, radiation necrosis, and epilepsy.

OBJECTIVE

To review the role of LITT in the treatment of recurrent HGGs, for which current treatments have limited efficacy, and to discuss the possible role of LITT in the disruption of the blood-brain barrier to increase delivery of chemotherapy locoregionally.

METHODS

A MEDLINE search was performed to identify 17 articles potentially appropriate for review. Of these 17, 6 reported currently commercially available systems and as well as magnetic resonance thermometry to monitor the ablation and, thus, were thought to be most appropriate for this review. These studies were then reviewed for complications associated with LITT. Ablation volume, tumor coverage, and treatment times were also reviewed.

RESULTS

Sixty-four lesions in 63 patients with recurrent HGGs were treated with LITT. Frontal (n = 34), temporal (n = 14), and parietal (n = 16) were the most common locations. Permanent neurological deficits were seen in 7 patients (12%), vascular injuries occurred in 2 patients (3%), and wound infection was observed in 1 patient (2%). Ablation coverage of the lesions ranged from 78% to 100%.

CONCLUSION

Although experience using LITT for recurrent HGGs is growing, current evidence is insufficient to offer a recommendation about its role in the treatment paradigm for recurrent HGGs.

ABBREVIATIONS

BBB, blood-brain barrierFDA, US Food and Drug AdministrationGBM, glioblastoma multiformeHGG, high-grade gliomaLITT, laser interstitial thermal therapy.

Laser Ablation of Newly Diagnosed Malignant Gliomas: a Meta-Analysis

BACKGROUND

Magnetic resonance-guided laser-interstitial thermotherapy (MR-LITT) is a minimally invasive technique that shows promise in neuro-oncology because of its superiority in delivering precise minimally invasive thermal energy with minimal collateral damage.

OBJECTIVE

In this analysis, we investigate initial data on the use of MR-LITT in the treatment of newly diagnosed high-grade gliomas.

METHODS

With the use of the PubMed, OVID, and Google-scholar database systems, a comprehensive search of the English literature was performed. Eighty-five articles were identified plus 1 that is pending publication. Four articles were accounted for in this review, including 25 patients with newly diagnosed high-grade gliomas who underwent MR-LITT treatment. We evaluated safety, progression-free survival, and overall survival.

RESULTS

Twenty-five patients with a mean age of 53.8 years underwent LITT treatments. On average, 82.9% of the pretreatment lesion volume was ablated. The average tumor volume treated was 16.5 cm. The mean follow-up time was 7.6 months. Median overall survival was found to be 14.2 months (range 0.1-23 months). The median progression-free survival was 5.1 months (range 2.4-23 months); however, these data are limited by the relatively short follow-up of the patients reviewed and small sample size of only 25 patients. There was 1 (3.4%) major perioperative complication, which was a central nervous system infection.

CONCLUSION

MR-LITT is a promising technology for the treatment of small, yet difficult-to-treat newly diagnosed high-grade gliomas. This study demonstrates that MR-LITT is safe, and future randomized studies are needed to evaluate its role as a treatment adjunct for newly diagnosed high-grade gliomas.

ABBREVIATIONS

BBB, blood-brain barrierHGG, high-grade gliomaLITT, laser-interstitial thermal therapyWHO, World Health Organization.

Image-guided thermal ablation with MR-based thermometry

Thermal ablation techniques such as radiofrequency, microwave, high intensity focused ultrasound (HIFU) and laser have been used as minimally invasive strategies for the treatment of variety of cancers. MR thermometry methods are readily available for monitoring thermal distribution and deposition in real time, leading to decrease of incidents of normal tissue damage around targeted lesion. HIFU and laser-induced thermal therapy (LITT) are the two widely accepted tumor ablation techniques because of their compatibility with MR systems. MRI provides multiple temperature dependent parameters for thermal imaging, such as signal intensity, T1, T2, diffusion coefficient, magnetization transfer, proton resonance frequency shift (PRFS, including phase imaging and spectroscopy) as well as frequency shift of temperature sensitive contrast agents. Absolute temperature mapping techniques, including both spectroscopic imaging using metabolites as a reference and phase imaging using fat as a reference, are immune to susceptibility effects and are not dependent on phase differences. These techniques are intrinsically more reliable than relative temperature measurement by phase mapping methods. If the limitation of low temporal and spatial resolution could be overcome, these methods may be preferred for MR-guided thermal ablation systems. As of today, the most popular MR thermal imaging method applied in tumor thermal ablation surgery is, however, still PRFS based phase mapping technique, which only provides relative temperature change and is prone to motion artifacts.

[Stereotactic laser thermocoagulation in epilepsy surgery]

In common with other stereotactic procedures, stereotactic laser thermocoagulation (SLT) promises gentle destruction of pathological tissue, which might become especially relevant for epilepsy surgery in the future. Compared to standard resection, no large craniotomy is necessary, cortical damage during access to deep-seated lesions can be avoided and interventions close to eloquent brain areas become possible. We describe the history and rationale of laser neurosurgery as well as the two available SLT systems (Visualase® and NeuroBlate®; CE marks pending). Both systems are coupled with magnetic resonance imaging (MRI) and MR thermometry, thereby increasing patient safety. We report the published clinical experiences with SLT in epilepsy surgery (altogether approximately 200 cases) with respect to complications, brain structural alterations, seizure outcome, neuropsychological findings and treatment costs. The rate of seizure-free patients seems to be slightly lower than for resection surgery. Due to the inadequate quality of studies, the neuropsychological superiority of SLT has not yet been unambiguously demonstrated.

Stereotactic Laser Ablation for Medically Intractable Epilepsy: The Next Generation of Minimally Invasive Epilepsy Surgery

Epilepsy is a common, disabling illness that is refractory to medical treatment in approximately one-third of patients, particularly among those with mesial temporal lobe epilepsy. While standard open mesial temporal resection is effective, achieving seizure freedom in most patients, efforts to develop safer, minimally invasive techniques have been underway for over half a century. Stereotactic ablative techniques, in particular, radiofrequency (RF) ablation, were first developed in the 1960s, with refinements in the 1990s with the advent of modern computed tomography and magnetic resonance-based imaging. In the past 5 years, the most recent techniques have used MRI-guided laser interstitial thermotherapy (LITT), the development of which began in the 1980s, saw refinements in MRI thermal imaging through the 1990s, and was initially used primarily for the treatment of intracranial and extracranial tumors. The present review describes the original stereotactic ablation trials, followed by modern imaging-guided RF ablation series for mesial temporal lobe epilepsy. The developments of LITT and MRI thermometry are then discussed. Finally, the two currently available MRI-guided LITT systems are reviewed for their role in the treatment of mesial temporal lobe and other medically refractory epilepsies.

Magnetic resonance-guided laser interstitial thermal therapy: report of a series of pediatric brain tumors

OBJECTIVE Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a novel, minimally invasive treatment that has multiple advantages in pediatric use and broad applicability for different types of lesions. Here, the authors report the preliminary results of the first series of pediatric brain tumors treated with MRgLITT at Golisano Children's Hospital in Syracuse, New York. METHODS Pediatric brain tumors treated with MRgLITT between February 2012 and August 2014 at Golisano Children's Hospital were evaluated retrospectively. Medical records, radiological findings, surgical data, complications, and results of tumor volumetric analyses were reviewed. The Visualase thermal laser system (Medtronic) was used in all MRgLITT procedures. RESULTS This series included 11 patients with 12 tumors (pilocytic astrocytoma, ependymoma, medulloblastoma, choroid plexus xanthogranuloma, subependymal giant cell astrocytoma, and ganglioglioma). A single laser and multiple overlapping ablations were used for all procedures. The mean laser dose was 10.23 W, and the mean total ablation time was 68.95 seconds. The mean initial target volume was 6.79 cm(3), and the mean immediate post-ablation volume was 7.86 cm(3). The mean hospital stay was 3.25 days, and the mean follow-up time was 24.5 months. Tumor volume decreased in the first 3 months after surgery (n = 11; p = 0.007) and continued to decrease by the 4- to 6-month followup (n = 11; mean volume 2.61 cm(3); p = 0.009). Two patients experienced post-ablation complications: transient right leg weakness in one patient, and transient hemiparesis, akinetic mutism, and eye movement disorder in the other. CONCLUSIONS Magnetic resonance-guided laser interstitial thermal therapy is an effective first- or second-line treatment for select pediatric brain tumors. Larger multiinstitutional clinical trials are necessary to evaluate its use for different types of lesions to further standardize practices.

Tissue Ablation Dynamics During Magnetic Resonance-Guided, Laser-Induced Thermal Therapy

BACKGROUND

Magnetic resonance-guided, laser-induced thermal therapy is a real-time magnetic resonance thermometry-guided, minimally invasive procedure used in the treatment of intracranial tumors, epilepsy, and pain. Little is known about its dynamics and the effects of various pathologies on overall ablation.

OBJECTIVE

To determine the relationship between thermal energy delivery and the time to maximal estimated thermal damage and whether differences exist between various intracranial pathologies.

METHODS

We used real-time ablation data from 28 patients across 5 unique intracranial pathologies. All ablations were performed using the Visualase Thermal Therapy System (Medtronic, Inc, Minneapolis, Minnesota), which uses a 980-nm diffusing tip diode laser. The thermal damage area was plotted against time for each ablation. We then estimated the duration of time required to reach 50% (t50) and 97% (t97) of maximal damage. Comparisons were then made between different intracranial pathologies.

RESULTS

The duration required to reach maximal thermal damage estimate (TDE) among all ablations was 159 ± 62 seconds, and the t50 and t97 were 43 ± 21 and 136 ± 57 seconds, respectively, where t97 was reached at an average of 23 seconds before the maximal TDE. The t97 was shorter in the recurrent metastasis/radiation necrosis and epilepsy groups compared with the previously untreated glioblastoma multiforme group.

CONCLUSION

The optimal duration can be estimated by the t97, which can be achieved in less than 3 minutes and differs across ablation targets. TDE expansion decelerates with prolonged ablation. Future studies are needed to examine the radiographic and clinical outcomes as well as the effects of ablation power, irrigation speed, and the effect of previous therapies on ablation dynamics.

Laser ablation therapy: An alternative treatment for medically resistant mesial temporal lobe epilepsy after age 50

Selective anterior mesial temporal lobe (AMTL) resection is considered a safe and effective treatment for medically refractory mesial temporal lobe epilepsy (MTLE). However, as with any open surgical procedure, older patients (aged 50+) face greater risks. Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) has shown recent potential as an alternative treatment for MTLE. As a less invasive procedure, MRgLITT could be particularly beneficial to older patients. To our knowledge, no study has evaluated the safety and efficacy of MRgLITT in this population. Seven consecutive patients (aged 50+) undergoing MRgLITT for MTLE were followed prospectively to assess surgical time, complications, postoperative pain control, length of stay (LOS), operating room (OR) charges, total hospitalization charges, and seizure outcome. Five of these patients were assessed at the 1-year follow-up for seizure outcome. These data were compared with data taken from 7 consecutive patients (aged 50+) undergoing AMTL resection. Both groups were of comparable age (mean: 60.7 (MRgLITT) vs. 53 (AMTL)). One AMTL resection patient had a complication of aseptic meningitis. One MRgLITT patient experienced an early postoperative seizure, and two MRgLITT patients had a partial visual field deficit. Seizure-freedom rates were comparable (80% (MRgLITT) and 100% (AMTL) (p>0.05)) beyond 1year postsurgery (mean follow-up: 1.0years (MRgLITT) vs. 1.8years (AMTL)). Mean LOS was shorter in the MRgLITT group (1.3days vs. 2.6days (p<0.05)). Neuropsychological outcomes were comparable. Short-term follow-up suggests that MRgLITT is safe and provides outcomes comparable to AMTL resection in this population. It also decreases pain medication requirement and reduces LOS. Further studies are necessary to assess the long-term efficacy of the procedure.

Accuracy of Laser Placement With Frameless Stereotaxy in Magnetic Resonance-Guided Laser-Induced Thermal Therapy

BACKGROUND

As magnetic resonance-guided laser-induced thermal therapy (MRgLITT) becomes more accepted, there needs to be an evaluation of the techniques required to achieve accurate laser placement.

OBJECTIVE

To report our experience with frameless stereotaxy and the ability to achieve accurate laser placements. We also evaluate the variables associated with proper placement.

METHODS

We performed a retrospective analysis from 3 years of MRgLITT. Demographics and operational parameters, including trajectory length, target alignment error, registration error, and radial error were recorded and compared. Blinded review was used for completeness of ablation.

RESULTS

In the study, 90 laser placements were evaluated for 72 cases. Trajectory length and target alignment error was 95.3 ± 26.0 mm and 0.7 ± 0.3 mm, respectively. Significant differences existed in registration error between 4 (0.6 ± 0.3 mm) and 5 (0.5 ± 0.2 mm) skull pins (P = .04), but no significant decreases in registration error as additional skull pins were registered. Fifteen laser placements resulted in subtotal ablations. The overall radial error using frameless stereotaxy was 0.9 ± 1.6 mm. In the study, 65% of lasers were exactly on the planned trajectory. Of the 30 that were not, the radial error = 2.6 ± 1.9 mm. Radial error of subtotal laser ablations was 0.5 ± 0.9 (range, 0-2.8 mm) and was not significantly different from 0.8 ± 1.7 (range, 0-7.1 mm) radial error of lasers with total ablations (P = .52). Lasers with radial error &gt;0 mm resulted in an incomplete ablation in 26.7% of cases.

CONCLUSION

Skull pin-based frameless stereotaxy for MRgLITT results in consistent accuracy, with the majority of cases resulting in complete ablations. A significant proportion of lasers with RE &gt;0 mm still result in complete ablations.

Stereotactic laser ablation of high-grade gliomas

Evolving research has demonstrated that surgical cytoreduction of a high-grade glial neoplasm is an important factor in improving the prognosis of these difficult tumors. Recent advances in intraoperative imaging have spurred the use of stereotactic laser ablation (laser interstitial thermal therapy [LITT]) for intracranial lesions. Among other targets, laser ablation has been used in the focal treatment of high-grade gliomas (HGGs). The revived application of laser ablation for gliomas parallels major advancements in intraoperative adjuvants and groundbreaking molecular advances in neuro-oncology. The authors review the research on stereotactic LITT for the treatment of HGGs and provide a potential management algorithm for HGGs that incorporates LITT in clinical practice.

Current Applications of MRI-Guided Laser Interstitial Thermal Therapy in the Treatment of Brain Neoplasms and Epilepsy: A Radiologic and Neurosurgical Overview

Minimally invasive stereotactic tumor ablation is a viable option for the treatment of benign and malignant intracranial lesions. Although surgical excision constitutes first-line therapy for various brain pathologies, it can cause irreversible neurologic deficits. Additionally, many patients who may benefit from surgery do not qualify as surgical candidates due to multiple comorbidities. Recent advancements in laser interstitial thermal therapy, namely the ability to monitor ablation in real-time under MR imaging, have improved the safety and efficacy of the procedure. MRI-guided laser interstitial thermal therapy is currently used as a minimally invasive treatment for brain metastases, radiation necrosis, glioma, and epilepsy. This article will discuss the principles, suggested indications, complications, and imaging characteristics of MRI-guided laser interstitial thermal therapy as they pertain to the treatment of brain pathology.

Renaissance of laser interstitial thermal ablation

Laser interstitial thermal therapy (LITT) is a minimally invasive technique for treating intracranial tumors, originally introduced in 1983. Its use in neurosurgical procedures was historically limited by early technical difficulties related to the monitoring and control of the extent of thermal damage. The development of magnetic resonance thermography and its application to LITT have allowed for real-time thermal imaging and feedback control during laser energy delivery, allowing for precise and accurate provision of tissue hyperthermia. Improvements in laser probe design, surgical stereotactic targeting hardware, and computer monitoring software have accelerated acceptance and clinical utilization of LITT as a neurosurgical treatment alternative. Current commercially available LITT systems have been used for the treatment of neurosurgical soft-tissue lesions, including difficult to access brain tumors, malignant gliomas, and radiosurgery-resistant metastases, as well as for the ablation of such lesions as epileptogenic foci and radiation necrosis. In this review, the authors aim to critically analyze the literature to describe the advent of LITT as a neurosurgical, laser excision tool, including its development, use, indications, and efficacy as it relates to neurosurgical applications.

Laser ablation as treatment strategy for medically refractory dominant insular epilepsy: therapeutic and functional considerations

Since its introduction to neurosurgery in 2008, laser ablative techniques have been largely confined to the management of unresectable tumors. Application of this technology for the management of focal epilepsy in the adult population has not been fully explored. Given that nearly 1,000,000 Americans live with medically refractory epilepsy and current surgical techniques only address a fraction of epileptic pathologies, additional therapeutic options are needed. We report the successful treatment of dominant insular epilepsy in a 53-year-old male with minimally invasive laser ablation complicated by mild verbal and memory deficits. We also report neuropsychological test data on this patient before surgery and at 8 months after the ablation procedure. This account represents the first reported successful patient outcome of laser ablation as an effective treatment option for medically refractory post-stroke epilepsy in an adult.

Magnetic resonance imaging-guided focused laser interstitial thermal therapy for intracranial lesions: single-institution series

BACKGROUND:

Surgical treatments for deep-seated intracranial lesions have been limited by morbidities associated with resection. Real-time magnetic resonance imaging–guided focused laser interstitial thermal therapy (LITT) offers a minimally invasive surgical treatment option for such lesions.

OBJECTIVE:

To review treatments and results of patients treated with LITT for intracranial lesions at Washington University School of Medicine.

METHODS:

In a review of 17 prospectively recruited LITT patients (34-78 years of age; mean, 59 years), we report demographics, treatment details, postoperative imaging characteristics, and peri- and postoperative clinical courses.

RESULTS:

Targets included 11 gliomas, 5 brain metastases, and 1 epilepsy focus. Lesions were lobar (n = 8), thalamic/basal ganglia (n = 5), insular (n = 3), and corpus callosum (n = 1). Mean target volume was 11.6 cm³, and LITT produced 93% target ablation. Patients with superficial lesions had shorter intensive care unit stays. Ten patients experienced no perioperative morbidities. Morbidities included transient aphasia, hemiparesis, hyponatremia, deep venous thrombosis, and fatal meningitis. Postoperative magnetic resonance imaging showed blood products within the lesion surrounded by new thin uniform rim of contrast enhancement and diffusion restriction. In conjunction with other therapies, LITT targets often showed stable or reduced local disease. Epilepsy focus LITT produced seizure freedom at 8 months. Preliminary overall median progression-free survival and survival from LITT in tumor patients were 7.6 and 10.9 months, respectively. However, this small cohort has not been followed for a sufficient length of time, necessitating future outcomes studies.

CONCLUSION:

Early peri- and postoperative clinical data demonstrate that LITT is a safe and viable ablative treatment option for intracranial lesions, and may be considered for select patients.

ABBREVIATION:

LITT, laser interstitial thermal therapy

Laser induced thermal therapy (LITT) for pediatric brain tumors: case-based review

Integration of Laser induced thermal therapy (LITT) to magnetic resonance imaging (MRI) have created new options for treating surgically challenging tumors in locations that would otherwise have represented an intrinsic comorbidity by the approach itself. As new applications and variations of the use are discussed, we present a case-based review of the history, development, and subsequent updates of minimally invasive MRI-guided laser interstitial thermal therapy (MRgLITT) ablation in pediatric brain tumors.

The role of laser interstitial thermal therapy in enhancing progression-free survival of difficult-to-access high-grade gliomas: a multicenter study

Surgical extent-of-resection has been shown to have an impact on high-grade glioma (HGG) outcomes; however, complete resection is rarely achievable in difficult-to-access (DTA) tumors. Controlled thermal damage to the tumor may have the same impact in DTA-HGGs. We report our multicenter results of laser interstitial thermal therapy (LITT) in DTA-HGGs. We retrospectively reviewed 34 consecutive DTA-HGG patients (24 glioblastoma, 10 anaplastic) who underwent LITT at Cleveland Clinic, Washington University, and Wake Forest University (May 2011-December 2012) using the NeuroBlate(®) System. The extent of thermal damage was determined using thermal damage threshold (TDT) lines: yellow TDT line (43 °C for 2 min) and blue TDT line (43°C for 10 min). Volumetric analysis was performed to determine the extent-of-coverage of tumor volume by TDT lines. Patient outcomes were evaluated statistically. LITT was delivered as upfront in 19 and delivered as salvage in 16 cases. After 7.2 months of follow-up, 71% of cases demonstrated progression and 34% died. The median overall survival (OS) for the cohort was not reached; however, the 1-year estimate of OS was 68 ± 9%. Median progression-free survival (PFS) was 5.1 months. Thirteen cases who met the following two criteria-(1) <0.05 cm(3) tumor volume not covered by the yellow TDT line and (2) <1.5 cm(3) additional tumor volume not covered by the blue TDT line-had better PFS than the other 21 cases (9.7 vs. 4.6 months; P = 0.02). LITT can be used effectively for treatment of DTA-HGGs. More complete coverage of tumor by TDT lines improves PFS which can be translated as the extent of resection concept for surgery.

Advances in therapy for melanoma brain metastases

Melanoma cells frequently metastasize to the brain, and approximately 50% of patients with metastatic melanoma develop intracranial disease. Historically, central nervous system dissemination has portended a very poor prognosis. Recent advances in systemic therapies for melanoma, supported by improved local therapy control of brain lesions, have resulted in better median survival for these patients. We review current local and systemic approaches for patients with melanoma brain metastases.

The use of MRI-guided laser-induced thermal ablation for epilepsy

PURPOSE

Epilepsy surgery is constantly researching for new options for patients with refractory epilepsy. MRI-guided laser-induced thermal ablation for epilepsy is an exciting new minimally invasive technology with an emerging use for lesionectomy of a variety of epileptogenic focuses (hypothalamic hamartomas, cortical dysplasias, cortical malformations, tubers) or as a disconnection tool allowing a new option of treatment without the hassles of an open surgery.

METHODS

MRI-guided laser interstitial thermal therapy (MRgLITT) is a procedure for destroying tissue-using heat. To deliver this energy in a minimally invasive fashion, a small diameter fiber optic applicator is inserted into the lesion through a keyhole stereotactic procedure. The thermal energy induces damage to intracellular DNA and DNA-binding structures, ultimately leading to cell death. The ablation procedure is supervised by real-time MRI thermal mapping and confirmed by immediate post-ablation T1 or FLAIR MRI images.

RESULTS

The present report includes an overview of the development and practice of an MR-guided laser ablation therapy known as MRI-guided laser interstitial thermal therapy (MRgLITT). The role of modern image-guided trajectory planning in MRgLITT will also be discussed, with particular emphasis on the treatment of refractory epilepsy using this novel, minimally invasive technique.

CONCLUSION

MRI-guided laser-induced thermal ablation for epilepsy is an exciting new minimally invasive technology that finds potential new applications every day in the neurosurgical field. It certainly brings a new perspective on the way we practice epilepsy surgery even though long-term results should be properly collected and analyzed.

Magnetic resonance imaging-guided focused laser interstitial thermal therapy for subinsular metastatic adenocarcinoma: technical case report

BACKGROUND AND IMPORTANCE

To describe the novel use of the AutoLITT System (Monteris Medical, Winnipeg, Manitoba, Canada) for focused laser interstitial thermal therapy (LITT) with intraoperative magnetic resonance imaging (MRI) and stereotactic image guidance for the treatment of metastatic adenocarcinoma in the left insula.

CLINICAL PRESENTATION

The patient was a 61-year-old right-handed man with a history of metastatic adenocarcinoma of the colon. He had previously undergone resection of multiple lesions, Gamma Knife radiosurgery, and whole-brain radiation. Despite treatment of a left insular tumor, serial imaging revealed that the lesion continued to enlarge. Given the refractory nature of this tumor to radiation and the deep-seated location, the patient elected to undergo LITT treatment. The center of the lesion and entry point on the scalp were identified with STEALTH (Medtronic, Memphis, Tennessee) image-guided navigation. The AXiiiS Stereotactic Miniframe (Monteris Medical) for the LITT system was secured onto the skull, and a trajectory was defined to achieve access to the centroid of the tumor. After a burr hole was made, a gadolinium template probe was inserted into the AXiiiS base. The trajectory was confirmed via an intraoperative MRI, and the LITT probe driver was attached to the base and CO2-cooled, side-firing laser LITT probe. The laser was activated and thermometry images were obtained. Two trajectories, posteromedial and anterolateral, produced satisfactory tumor ablation.

CONCLUSION

LITT with intraoperative MRI and stereotactic image guidance is a newly available, minimally invasive, and therapeutically viable technique for the treatment of deep seated brain tumors.