Neurotrophic Factor Protection against Excitotoxic Neuronal Death

Neurotrophic factors are polypeptides capable of promoting neuronal survival in both the developing and the adult brain. In addition to the neurotrophins, NGF, brain-derived neurotropic factor, and NT-3 to -6, other neurotrophic factors include ciliary neurotrophic factor, fibroblast growth factors, insulin-like growth factors, members of the transforming growth factor superfamily, members of the epidermal growth factor family, and other cytokines such as leukemia inhibitory factor, oncostatin M, and interleukins-6 and -11. One condition under which these factors promote survival is the challenge of neurons with analogs of excitatory amino acid transmitters. Such analogs, including quinolinic acid, kainic acid, and ibotenic acid, are frequently employed as models of neurological diseases such as Huntington's disease, Parkinson's disease, Alzheimer's disease, epilepsy, cerebellar degenerations, and amyotrophic lateral sclerosis. Excitotoxicity also plays a role in neu ronal death caused by focal ischemia, hypoglycemia, or trauma. Although much has been learned about the mechanisms of both the action of neurotrophic factors and of cell death in response to excitotoxins, the mechanism of protection by these factors remains uncertain. This review explores the biochemical and phys iological changes mediated by neurotrophic factors that may underlie their ability to protect against excito toxic cell death. Second messenger pathways used degenerately by both excitotoxins and neurotrophic factors are discussed as a potential site of interaction mediating the protective effects of neurotrophic factors. Particular attention is also paid to the importance of the route of neurotrophic factor delivery in conferring neuroprotection in particular excitotoxic models. The Neuroscientist 1:286-297, 1995

Impact of systemic targeted agents on the clinical outcomes of patients with brain metastases

BACKGROUND

To determine the clinical benefits of systemic targeted agents across multiple histologies after stereotactic radiosurgery (SRS) for brain metastases.

METHODS

Between 2000 and 2013, 737 patients underwent upfront SRS for brain metastases. Patients were stratified by whether or not they received targeted agents with SRS. 167 (23%) received targeted agents compared to 570 (77%) that received other available treatment options. Time to event data were summarized using Kaplan-Meier plots, and the log rank test was used to determine statistical differences between groups.

RESULTS

Patients who received SRS with targeted agents vs those that did not had improved overall survival (65% vs. 30% at 12 months, p < 0.0001), improved freedom from local failure (94% vs 90% at 12 months, p = 0.06), improved distant failure-free survival (32% vs. 18% at 12 months, p = 0.0001) and improved freedom from whole brain radiation (88% vs. 77% at 12 months, p = 0.03). Improvement in freedom from local failure was driven by improvements seen in breast cancer (100% vs 92% at 12 months, p < 0.01), and renal cell cancer (100% vs 88%, p = 0.04). Multivariate analysis revealed that use of targeted agents improved all cause mortality (HR = 0.6, p < 0.0001).

CONCLUSIONS

Targeted agent use with SRS appears to improve survival and intracranial outcomes.

Local control of brain metastases after stereotactic radiosurgery: the impact of whole brain radiotherapy and treatment paradigm

PURPOSE

We investigate clinical, pathologic, and treatment paradigm-related factors affecting local control of brain metastases after stereotactic radiosurgery (SRS) with or without whole brain radiotherapy (WBRT).

METHODS AND MATERIALS

Patients with brain metastases treated with SRS alone, before or after WBRT were considered to determine predictors of local failure (LF), time to failure and survival.

RESULTS

Among 137 patients, 411 brain metastases were analyzed. 23% of patients received SRS alone, 51% received WBRT prior to SRS, and 26% received SRS followed by WBRT. LF occurred in 125 metastases: 63% after SRS alone, 20% after WBRT then SRS, and 22% after SRS then WBRT. Median time to local failure was significantly less after SRS alone compared to WBRT then SRS (12.1 v. 22.7 months, p=0.003). Tumor volume was significantly associated with LF (HR:5.2, p<0.001, 95% CI:3.4-7.8).

CONCLUSIONS

WBRT+SRS results in reduced LF. Local control was not significantly different after SRS as salvage therapy versus upfront SRS.

Predictors of trigeminal nerve dysfunction following stereotactic radiosurgery for trigeminal neuralgia

BACKGROUND/AIMS

To evaluate clinical and dosimetric predictors of trigeminal nerve dysfunction (TND) following stereotactic radiosurgery (SRS) for Trigeminal Neuralgia (TN).

METHODS

We retrospectively reviewed our cohort of 446 patients with TN who underwent SRS between 1999-2008. Median follow-up was 25.1 and 17.4 months (mo) in those with and without TND respectively. Dosimetric and anatomic measurements and clinical features including Burchiel subtype, pain quality, prior procedures, comorbidities, and medications were evaluated for their influence on the TND using univariate and multivariate logistic regression modeling.

RESULTS

TND was observed in 44.6% of patients and was similar across facial pain types. Those with TND had prolonged time to pain relapse [(TND, 68.48 mo) vs. (No TND, 29.37 mo)]. Multivariate analysis identified sharp pain at diagnosis (OR 0.594; 95%CI 0.38-0.91), and dorsal root entry zone (DREZ) maximum dose (OR 1.022; 95%CI 1.00-1.04) as predictors of TND.

CONCLUSIONS

The presence of sharp pain and increasing DREZ maximum dose were independently associated with TND. Patients with atypical facial pain were at lower risk of TND with increasing dose relative to Type 1 and Type 2 TN.

Association between subthalamic nucleus deep brain stimulation and weight gain: Results of a case-control study

OBJECTIVE

To evaluate whether weight change in patients with Parkinson's disease (PD) is different in those undergoing deep brain stimulation (DBS) of the subthalamic nucleus (STN) compared to those not undergoing DBS.

PATIENTS AND METHODS

A retrospective case-control study was performed in PD patients who had undergone STN DBS (cases) compared to matched PD patients without DBS (controls). Demographic and clinical data including Unified Parkinson's Disease Rating Scale (UPDRS) motor scores were collected. Repeated measures mixed model regression was used to identify variables associated with weight gain.

RESULTS

Thirty-five cases and 34 controls were identified. Baseline age, gender, diagnosis and weight were similar. Duration of diagnosis was longer in cases (6.3 vs 4.9 years, p=0.0015). At 21.3 months, cases gained 2.9 kg (+4.65%) while controls lost 1.8 kg (-3.05%, p<0.02). Postoperative UPDRS motor scores improved by 49% indicating surgical efficacy. Only younger age (p=0.0002) and DBS (p=0.008) were significantly associated with weight gain.

CONCLUSION

In this case-control study, PD patients undergoing STN DBS experienced post-operative weight gain that was significantly different from the weight loss observed in non-DBS PD controls. Patients, especially overweight individuals, should be informed that STN DBS can result in weight gain.

Repeat Radiosurgery for Trigeminal Neuralgia

BACKGROUND

Repeat Gamma Knife radiosurgery (GKRS) is an established option for patients whose pain has recurred after the initial procedure, with reported success rates varying from 68% to 95%. Predictive factors for response to the repeat GKRS are ill-defined.

OBJECTIVE

This cohort study aimed to report the outcomes and factors predictive of success for patients who have undergone repeated GKRS for trigeminal neuralgia at Wake Forest University Baptist Medical Center.

METHODS

Between 1999 and 2013, 152 patients underwent repeat GKRS at Wake Forest, 125 of whom were available for long-term follow-up. A retrospective chart review and telephone interviews were conducted to determine background medical history, dosimetric data, outcomes, and adverse effects of the procedure.

RESULTS

Eighty-four percent of patients achieved at least Barrow Neurological Institute (BNI) IIIb pain relief, with 46% achieving BNI I. The 1-, 3-, and 5-year rates of BNI I pain relief were 63%, 50%, and 37%, respectively. The 1-, 3-, and 5-year rates of BNI IIIb or better pain relief were 74%, 59%, and 46%, respectively. One patient experienced bothersome numbness and 2 patients developed anesthesia dolorosa. The dominant predictive factors for pain relief were facial numbness after the first GKRS and a positive pain response to the first GKRS.

CONCLUSION

Repeat GKRS is an effective method of treating recurrent trigeminal neuralgia. Patients who have facial numbness after the first treatment and a positive pain response to the first GKRS are significantly more likely to respond well to the second treatment.

Short pauses in thalamic deep brain stimulation promote tremor and neuronal bursting

OBJECTIVE

We conducted intraoperative measurements of tremor during DBS containing short pauses (⩽50 ms) to determine if there is a minimum pause duration that preserves tremor suppression.

METHODS

Nine subjects with ET and thalamic DBS participated during IPG replacement surgery. Patterns of DBS included regular 130 Hz stimulation interrupted by 0, 15, 25 or 50 ms pauses. The same patterns were applied to a model of the thalamic network to quantify effects of pauses on activity of model neurons.

RESULTS

All patterns of DBS decreased tremor relative to 'off'. Patterns with pauses generated less tremor reduction than regular high frequency DBS. The model revealed that rhythmic burst-driver inputs to thalamus were masked during DBS, but pauses in stimulation allowed propagation of bursting activity. The mean firing rate of bursting-type model neurons as well as the firing pattern entropy of model neurons were both strongly correlated with tremor power across stimulation conditions.

CONCLUSIONS

The temporal pattern of stimulation influences the efficacy of thalamic DBS. Pauses in stimulation resulted in decreased tremor suppression indicating that masking of pathological bursting is a mechanism of thalamic DBS for tremor.

SIGNIFICANCE

Pauses in stimulation decreased the efficacy of open-loop DBS for suppression of tremor.

Neurosurgical Techniques for Disruption of the Blood-Brain Barrier for Glioblastoma Treatment

The blood-brain barrier remains a main hurdle to drug delivery to the brain. The prognosis of glioblastoma remains grim despite current multimodal medical management. We review neurosurgical technologies that disrupt the blood-brain barrier (BBB). We will review superselective intra-arterial mannitol infusion, focused ultrasound, laser interstitial thermotherapy, and non-thermal irreversible electroporation (NTIRE). These technologies can lead to transient BBB and blood-brain tumor barrier disruption and allow for the potential of more effective local drug delivery. Animal studies and preliminary clinical trials show promise for achieving this goal.

Competing Risk Analysis of Neurologic versus Nonneurologic Death in Patients Undergoing Radiosurgical Salvage After Whole-Brain Radiation Therapy Failure: Who Actually Dies of Their Brain Metastases?

PURPOSE

To estimate the hazard for neurologic (central nervous system, CNS) and nonneurologic (non-CNS) death associated with patient, treatment, and systemic disease status in patients receiving stereotactic radiosurgery after whole-brain radiation therapy (WBRT) failure, using a competing risk model.

PATIENTS AND METHODS

Of 757 patients, 293 experienced recurrence or new metastasis following WBRT. Univariate Cox proportional hazards regression identified covariates for consideration in the multivariate model. Competing risks multivariable regression was performed to estimate the adjusted hazard ratio (aHR) and 95% confidence interval (CI) for both CNS and non-CNS death after adjusting for patient, disease, and treatment factors. The resultant model was converted into an online calculator for ease of clinical use.

RESULTS

The cumulative incidence of CNS and non-CNS death at 6 and 12 months was 20.6% and 21.6%, and 34.4% and 35%, respectively. Patients with melanoma histology (relative to breast) (aHR 2.7, 95% CI 1.5-5.0), brainstem location (aHR 2.1, 95% CI 1.3-3.5), and number of metastases (aHR 1.09, 95% CI 1.04-1.2) had increased aHR for CNS death. Progressive systemic disease (aHR 0.55, 95% CI 0.4-0.8) and increasing lowest margin dose (aHR 0.97, 95% CI 0.9-0.99) were protective against CNS death. Patients with lung histology (aHR 1.3, 95% CI 1.1-1.9) and progressive systemic disease (aHR 2.14, 95% CI 1.5-3.0) had increased aHR for non-CNS death.

CONCLUSION

Our nomogram provides individual estimates of neurologic death after salvage stereotactic radiosurgery for patients who have failed prior WBRT, based on histology, neuroanatomical location, age, lowest margin dose, and number of metastases after adjusting for their competing risk of death from other causes.

Gamma Knife radiosurgery for meningiomas in patients with neurofibromatosis Type 2

OBJECT

Neurofibromatosis Type 2 (NF2) is a rare autosomal dominant disorder predisposing patients to meningiomatosis. The role of stereotactic radiosurgery (SRS) is poorly defined in NF2, and although the procedure has excellent control rates in the non-NF2 population, its utility has been questioned because radiation has been hypothesized to predispose patients to malignant transformation of benign tumors. To the authors' knowledge, this is the first study to examine the use of SRS specifically for meningiomas in patients with NF2.

METHODS

The authors searched a tumor registry for all patients with NF2 who had undergone Gamma Knife radiosurgery (GKRS) for meningioma in the period from January 1, 1999, to September 19, 2013, at a single tertiary care cancer center. Medical records were retrospectively reviewed for patient and tumor characteristics and outcomes.

RESULTS

Among the 12 patients who met the search criteria, 125 meningiomas were identified, 87 (70%) of which were symptomatic or progressive and thus treated with GKRS. The median age at the first GKRS was 31 years (interquartile range [IQR] 27-37 years). Five patients (42%) had multiple treatments with a median of 27 months (IQR 14-50 months) until the subsequent GKRS. The median follow-up in surviving patients was 43 months (IQR 34-110 months). The 5-year local tumor control and distant treatment failure rates were 92% and 77%, respectively. Toxicities occurred in 25% of the GKRS treatments, although the majority were Grade 1 or 2. At the last follow-up, 4 patients (33%) had died a neurological death at a median age of 39 years (IQR 37-46 years), and their cases accounted for 45% of all tumors, 55% of all treated tumors, and 58% of all GKRSs. Univariate analysis revealed several predictive variables for distant failure, including male sex (HR 0.28, 95% CI 0.086-0.92, p = 0.036), age at distant failure (HR 0.92, 95% CI 0.90-0.95, p < 0.0001), and prior number of GKRS treatments (HR 1.2, 95% CI 1.1-1.4, p = 0.0049). Local failure, maximum size of the treated tumor, delivered tumor margin dose, and WHO grade were not significant. On multivariate analysis, age at distant failure (HR 0.91, 95% CI 0.88-0.95, p < 0.0001) and prior number of GKRSs (HR 1.3, 95% CI 1.1-1.5, p = 0.004) remained significant. No malignant transformation events among treated tumors were observed.

CONCLUSIONS

Radiosurgery represents a feasible modality with minimal toxicity for NF2-associated meningiomas. Increasing patient age was associated with a decreased rate of distant failure, whereas an increasing number of prior GKRS treatments predicted distant failure. Further studies are necessary to determine the long-term patterns of treatment failure in these patients.

Factors that determine local control with gamma knife radiosurgery: The role of primary histology

BACKGROUND

Stereotactic radiosurgery for the treatment of brain metastases is commonly delivered without regard to primary cancer histology. This study sought to determine if the primary site of origin for brain metastases affected the propensity for local failure.

METHODS

A total of 83 patients with 200 brain metastases were examined retrospectively for predictors of infield failure. Tumor, patient, and treatment characteristics were analyzed including primary tumor histology, radiosurgical dose and age. Cox proportional hazards models, univariate and multivariate analyses were used to identify predictors of local failure.

RESULTS

Freedom from local failure for the entire population was 83% and 65% at 6 and 12 months, respectively. Multivariate analysis revealed that breast cancer brain metastases have a significantly lower risk of local failure than melanoma (HR = 0.31, p< 0.001). Additionally, multivariate analysis revealed that increasing dose lowered risk for local failure (HR = 0.87, p<0.001).

CONCLUSIONS

Melanoma histology leads to a higher rate of local failure. Higher prescription dose results in higher incidence of local control.

Influenza vaccine immunogenicity in patients with primary central nervous system malignancy

BACKGROUND

Patients with central nervous system (CNS) malignancies represent an "at-risk" population for contracting influenza, particularly if they are receiving ongoing chemotherapy, radiation, and/or glucocorticoid treatment. The Centers for Disease Control endorses vaccination for these patients, although data are not available to indicate whether they mount an immunologic response adequate to achieve clinical protection.

METHODS

A pilot prospective cohort study was designed to evaluate the immunogenicity of the standard-dose trivalent inactivated influenza vaccine in patients with malignant CNS tumors. Baseline data collection included diagnosis, chemotherapy, timing of chemotherapy or radiation relative to vaccination, and glucocorticoid dose. Serum samples were collected at baseline, day 14, day 28, and month 3 following vaccination. Samples were tested using hemagglutinin inhibition to determine seroconversion (4-fold rise in titer) and seroprotection (titer >1:40).

RESULTS

A total of 38 patients were enrolled (mean age, 54 years ±13.5 years, 60.5% male, 94.7% Caucasian, and 5.3% African American). CNS tumor diagnoses included glioblastoma multiforme (55.2%), other high-grade glioma (13.2%), low-grade glioma (15.8%), and primary CNS lymphoma (15.8%). At enrollment, 20 patients (52.6%) were taking glucocorticoids, 25 (65.8%) were on active chemotherapy, and 3 (7.9%) were undergoing radiation. Seroconversion rates at day 28 for the A/H1N1, A/H3N2, and B strains were 37%, 23% and 23%, respectively. Seroprotection was 80%, 69%, and 74%, respectively. All rates were significantly lower than published rates in healthy adults (P < .001).

CONCLUSION

Influenza vaccine immunogenicity is significantly reduced in patients with CNS malignancies. Future studies are needed to determine the causative etiologies and appropriate vaccination strategies.

Predictors of survival, neurologic death, local failure, and distant failure after gamma knife radiosurgery for melanoma brain metastases

OBJECTIVE

This study sought to assess clinical outcomes in patients receiving gamma knife radiosurgery (GK) for treatment of brain metastases from melanoma and evaluate for potential predictive factors.

METHODS

We reviewed 188 GK procedures in 129 consecutive patients that were treated for brain metastases from melanoma. The population consisted of 84 males and 45 females with a median age of 57 years. Fifty-five patients (43%) had a single metastasis. Seventy-one patients (55%) received chemotherapy, 58 patients (45%) received biologic agents, and 36 patients (28%) received prior whole brain radiation therapy (WBRT). The median marginal dose was 18.8 Gy (range 12 to 24 Gy).

RESULTS

Actuarial survival was 52%, 26%, and 13% at 6, 12, and 24 months, respectively. The median survival time was 6.7 months. Local tumor control was 95%, 81% 53% at 6, 12, and 24 months, respectively. The median time to LBF was 25.2 months. Freedom from distant brain failure was 40%, 29%, and 10% at 6, 12, and 24 months, and the median time to DBF was 4.6 months. At the time of data analysis, 108 patients (84%) had died. Fifty-eight patients (52%) died from neurologic death. The median time to neurologic death from GK treatment was 7.9 months. Multivariate analysis revealed that hemorrhage of metastases prior to GK (P = .02) and LBF (P = .03) were the dominant predictors of neurologic death.

CONCLUSIONS

GK achieves excellent local control and may improve outcomes as a component of a multidisciplinary treatment strategy. Distant brain failure and neurologic demise remain problematic and prospective trials are necessary.

Is There a Tumor Volume Threshold for Postradiosurgical Symptoms? A Single-Institution Analysis

BACKGROUND:

Single-fraction radiosurgery may carry a higher risk of symptomatic peritumoral edema than conventionally fractionated radiotherapy, with a reported incidence of 2.5% to 37%. Previous research has shown that larger tumor volume and margin dose &gt;14 Gy are associated with increased risk of toxicity. Parasagittal location has been associated with toxicity in some studies, but not in others.

OBJECTIVE:

To determine risk factors for and patterns of postradiosurgical symptoms (PRS).

METHODS:

This single-institution retrospective chart review included 282 stereotactic radiosurgery procedures for an intracranial meningioma from January 1999 to March 2011. PRS were assessed by using the Common Terminology Criteria for Adverse Events (Version 4.0). Statistical analyses were conducted by using the 194 procedures for which treatment plans were available.

RESULTS:

PRS were observed after 65 procedures (23%); 35 (12%) were grade 2 or higher. Posttreatment edema occurred in 21% of grade I PRS, 68% of grade II PRS, and 71% of grade III PRS. Tumor volume ≥7.1 cc (adjusted hazards ratio = 4.9, P = .02), prior external beam radiotherapy (adjusted hazards ratio = 2.6, P = .03), and histological grade (P = .005) predicted PRS. On multivariate analysis, parasagittal location was not predictive of PRS, although skull base location predicted a lower risk of symptomatic posttreatment edema (adjusted hazards ratio = 0.133, P = .02).

CONCLUSION:

In our series, prior external beam radiotherapy, tumor volume, and tumor grade are risk factors for PRS, while pretreatment edema approached statistical significance. Peritumoral edema is the predominant mechanism of significant PRS, and skull base tumors have a lower risk of posttreatment edema.

Risk factors for leptomeningeal carcinomatosis in patients with brain metastases who have previously undergone stereotactic radiosurgery

Our objective was to explore the hypothesis that the risk of leptomeningeal dissemination (LMD) in patients who underwent stereotactic radiosurgery (SRS) for brain metastases is influenced by the site of the primary cancer, the addition of whole brain radiation therapy (WBRT), surgical resection, and control over their systemic disease. We conducted a retrospective cohort analysis of 805 patients who were treated with SRS for brain metastases between 1999 and 2012 at the Wake Forest Baptist Medical Center, and excluded all patients with evidence of LMD before SRS. The primary outcome was LMD. Forty-nine of 795 patients developed LMD with a cumulative incidence of 6.2% (95% Confidence Interval (CI), 4.7-8.0). Median time from SRS to LMD was 7.4 months (Interquartile Range (IQR), 3.3-15.4). A colorectal primary site (Hazard Ratio (HR), 4.5; 95% CI 2.5-8.0; p < 0.0001), distant brain failure (HR, 2.0; 95% CI 1.2-3.2; p = 0.007), breast primary site (HR, 1.6; 95% CI 1.0-2.7; p = 0.05), the number of intracranial metastases at time of initial SRS (HR, 1.1; 95% CI 1.0-1.2; p = 0.02), and age (by 5-year interval) (HR, 0.9; 95% CI 0.8, 0.9; p = 0.0006) were independent factors associated with LMD. There was no evidence that surgical resection before SRS altered the risk of LMD (HR, 1.1; 95 % CI 0.6-2.0, p = 0.78). In patients who underwent SRS for brain metastases, a colorectal or breast primary site, distant brain failure, younger age, and an increased number of intracranial metastases were independently associated with LMD. Given its relative rarity as an outcome, multi-institutional prospective studies will likely be necessary to validate and quantify these relationships.

Comparison of clinical outcomes and genomic characteristics of single focus and multifocal glioblastoma

We investigate the differences in molecular signature and clinical outcomes between multiple lesion glioblastoma (GBM) and single focus GBM in the modern treatment era. Between August 2000 and May 2010, 161 patients with GBM were treated with modern radiotherapy techniques. Of this group, 33 were considered to have multiple lesion GBM (25 multifocal and 8 multicentric). Patterns of failure, time to progression and overall survival were compared based on whether the tumor was considered a single focus or multiple lesion GBM. Genomic groupings and methylation status were also investigated as a possible predictor of multifocality in a cohort of 41 patients with available tissue for analysis. There was no statistically significant difference in overall survival (p < 0.3) between the multiple lesion tumors (8.2 months) and single focus GBM (11 months). Progression free survival was superior in the single focus tumors (7.1 months) as compared to multi-focal (5.6 months, p = 0.02). For patients with single focus, multifocal and multicentric GBM, 81, 76 and 88 % of treatment failures occurred in the 60 Gy volume (p < 0.5), while 54, 72, and 38 % of treatment failures occurred in the 46 Gy volume (p < 0.4). Out of field failures were rare in both single focus and multiple foci GBM (7 vs 3 %). Genomic groupings and methylation status were not found to predict for multifocality. Patterns of failure, survival and genomic signatures for multiple lesion GBM do not appreciably differ when compared to single focus tumors.

Neuronal oscillations in Parkinson's disease

Parkinson's Disease (PD), characterized by tremor, rigidity, and bradykinesia, is one of the most prevalent neurodegenerative disorders in the world. The pathological hallmark of PD is the loss of dopaminergic cells in the substantia nigra and other brain regions. The pathophysiological mechanisms by which dopaminergic cell loss leads to the motor manifestations of PD are yet to be fully elucidated. A growing body of evidence has revealed abnormal neuronal oscillations within and between multiple brain regions in PD. Unique oscillatory patterns are associated with specific motor abnormalities in PD. Therapies, such as dopaminergic medication and deep brain stimulation that disrupt these abnormal neuronal oscillatory patterns produce symptomatic improvement in PD patients. These findings emphasize the importance of abnormal neuronal oscillations in the pathophysiology of PD, making the disruption of these oscillatory patterns a promising target in the development of effective PD treatments.

Multisurgeon, multisite validation of a trajectory planning algorithm for deep brain stimulation procedures

Deep brain stimulation, which is used to treat various neurological disorders, involves implanting a permanent electrode into precise targets deep in the brain. Reaching these targets safely is difficult because surgeons have to plan trajectories that avoid critical structures and reach targets within specific angles. A number of systems have been proposed to assist surgeons in this task. These typically involve formulating constraints as cost terms, weighting them by surgical importance, and searching for optimal trajectories, in which constraints and their weights reflect local practice. Assessing the performance of such systems is challenging because of the lack of ground truth and clear consensus on an optimal approach among surgeons. Due to difficulties in coordinating inter-institution evaluation studies, these have been performed so far at the sites at which the systems are developed. Whether or not a scheme developed at one site can also be used at another is thus unknown. In this paper, we conduct a study that involves four surgeons at three institutions to determine whether or not constraints and their associated weights can be used across institutions. Through a series of experiments, we show that a single set of weights performs well for all surgeons in our group. Out of 60 trajectories, our trajectories were accepted by a majority of neurosurgeons in 95% of the cases and the average acceptance rate was 90%. This study suggests, albeit on a limited number of surgeons, that the same system can be used to provide assistance across multiple sites and surgeons.

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.

Tumor histology predicts patterns of failure and survival in patients with brain metastases from lung cancer treated with gamma knife radiosurgery

BACKGROUND

We review our experience with lung cancer patients with newly diagnosed brain metastases treated with Gamma Knife radiosurgery (GKRS).

OBJECTIVE

To determine whether tumor histology predicts patient outcomes.

METHODS

Between July 1, 2000, and December 31, 2010, 271 patients with brain metastases from primary lung cancer were treated with GKRS at our institution. Included in our study were 44 squamous cell carcinoma (SCC), 31 small cell carcinoma (SCLC), and 138 adenocarcinoma (ACA) patients; 47 patients with insufficient pathology to determine subtype were excluded. No non-small cell lung cancer (NSCLC) patients received whole-brain radiation therapy (WBRT) before their GKRS, and SCLC patients were allowed to have prophylactic cranial irradiation, but no previously known brain metastases. A median of 2 lesions were treated per patient with median marginal dose of 20 Gy.

RESULTS

Median survival was 10.2 months for ACA, 5.9 months for SCLC, and 5.3 months for SCC patients (P = .008). The 1-year local control rates were 86%, 86%, and 54% for ACA, SCC, and SCLC, respectively (P = .027). The 1-year distant failure rates were 35%, 63%, and 65% for ACA, SCC, and SCLC, respectively (P = .057). The likelihood of dying of neurological death was 29%, 36%, and 55% for ACA, SCC, and SCLC, respectively (P = .027). The median time to WBRT was 11 months for SCC and 24 months for ACA patients (P = .04). Multivariate analysis confirmed SCLC histology as a significant predictor of worsened local control (hazard ratio [HR]: 6.46, P = .025) and distant failure (HR: 3.32, P = .0027). For NSCLC histologies, SCC predicted for earlier time to salvage WBRT (HR: 2.552, P = .01) and worsened overall survival (HR: 1.77, P < .0121).

CONCLUSION

Histological subtype of lung cancer appears to predict outcomes. Future trials and prognostic indices should take these histology-specific patterns into account.

Predictive nomogram for the durability of pain relief from gamma knife radiation surgery in the treatment of trigeminal neuralgia

PURPOSE

To determine factors associated with the durability of stereotactic radiation surgery (SRS) for treatment of trigeminal neuralgia (TN).

METHODS AND MATERIALS

Between 1999 and 2008, 446 of 777 patients with TN underwent SRS and had evaluable follow-up in our electronic medical records and phone interview records. The median follow-up was 21.2 months. The Barrow Neurologic Institute (BNI) pain scale was used to determine pre- and post-SRS pain. Dose-volume anatomical measurements, Burchiel pain subtype, pain quality, prior procedures, and medication usage were included in this retrospective cohort to identify factors impacting the time to BNI 4-5 pain relapse by using Cox proportional hazard regression. An internet-based nomogram was constructed based on predictive factors of durable relief pre- and posttreatment at 6-month intervals.

RESULTS

Rates of freedom from BNI 4-5 failure at 1, 3, and 5 years were 84.5%, 70.4%, and 46.9%, respectively. Pain relief was BNI 1-3 at 1, 3, and 5 years in 86.1%, 74.3%, and 51.3% of type 1 patients; 79.3%, 46.2%, and 29.3% of type 2 patients; and 62.7%, 50.2%, and 25% of atypical facial pain patients. BNI type 1 pain score was achieved at 1, 3, and 5 years in 62.9%, 43.5%, and 22.0% of patients with type 1 pain and in 47.5%, 25.2%, and 9.2% of type 2 patients, respectively. Only 13% of patients with atypical facial pain achieved BNI 1 response; 42% of patients developed post-Gamma Knife radiation surgery (GKRS) trigeminal dysfunction. Multivariate analysis revealed that post-SRS numbness (hazard ratio [HR], 0.47; P<.0001), type 1 (vs type 2) TN (HR, 0.6; P=.02), and improved post-SRS BNI score at 6 months (HR, 0.009; P<.0001) were predictive of a durable pain response.

CONCLUSIONS

The durability of SRS for TN depends on the presenting Burchiel pain type, the post-SRS BNI score, and the presence of post-SRS facial numbness. The durability of pain relief can be estimated pre- and posttreatment by using our nomogram for situations when the potential of relapse may guide the decision for initial intervention.

A nomogram for predicting distant brain failure in patients treated with gamma knife stereotactic radiosurgery without whole brain radiotherapy

BACKGROUND

We review our single institution experience to determine predictive factors for early and delayed distant brain failure (DBF) after radiosurgery without whole brain radiotherapy (WBRT) for brain metastases.

MATERIALS AND METHODS

Between January 2000 and December 2010, a total of 464 patients were treated with Gamma Knife stereotactic radiosurgery (SRS) without WBRT for primary management of newly diagnosed brain metastases. Histology, systemic disease, RPA class, and number of metastases were evaluated as possible predictors of DBF rate. DBF rates were determined by serial MRI. Kaplan-Meier method was used to estimate rate of DBF. Multivariate analysis was performed using Cox Proportional Hazard regression.

RESULTS

Median number of lesions treated was 1 (range 1-13). Median time to DBF was 4.9 months. Twenty-seven percent of patients ultimately required WBRT with median time to WBRT of 5.6 months. Progressive systemic disease (χ(2)= 16.748, P < .001), number of metastases at SRS (χ(2) = 27.216, P < .001), discovery of new metastases at time of SRS (χ(2) = 9.197, P < .01), and histology (χ(2) = 12.819, P < .07) were factors that predicted for earlier time to distant failure. High risk histologic subtypes (melanoma, her2 negative breast, χ(2) = 11.020, P < .001) and low risk subtypes (her2 + breast, χ(2) = 11.343, P < .001) were identified. Progressive systemic disease (χ(2) = 9.549, P < .01), number of brain metastases (χ(2) = 16.953, P < .001), minimum SRS dose (χ(2) = 21.609, P < .001), and widespread metastatic disease (χ(2) = 29.396, P < .001) were predictive of shorter time to WBRT.

CONCLUSION

Systemic disease, number of metastases, and histology are factors that predict distant failure rate after primary radiosurgical management of brain metastases.