Subsecond dopamine fluctuations in human striatum encode superposed error signals about actual and counterfactual reward.

In the mammalian brain, dopamine is a critical neuromodulator whose actions underlie learning, decision-making, and behavioral control. Degeneration of dopamine neurons causes Parkinson's disease, whereas dysregulation of dopamine signaling is believed to contribute to psychiatric conditions such as schizophrenia, addiction, and depression. Experiments in animal models suggest the hypothesis that dopamine release in human striatum encodes reward prediction errors (RPEs) (the difference between actual and expected outcomes) during ongoing decision-making. Blood oxygen level-dependent (BOLD) imaging experiments in humans support the idea that RPEs are tracked in the striatum; however, BOLD measurements cannot be used to infer the action of any one specific neurotransmitter. We monitored dopamine levels with subsecond temporal resolution in humans (n = 17) with Parkinson's disease while they executed a sequential decision-making task. Participants placed bets and experienced monetary gains or losses. Dopamine fluctuations in the striatum fail to encode RPEs, as anticipated by a large body of work in model organisms. Instead, subsecond dopamine fluctuations encode an integration of RPEs with counterfactual prediction errors, the latter defined by how much better or worse the experienced outcome could have been. How dopamine fluctuations combine the actual and counterfactual is unknown. One possibility is that this process is the normal behavior of reward processing dopamine neurons, which previously had not been tested by experiments in animal models. Alternatively, this superposition of error terms may result from an additional yet-to-be-identified subclass of dopamine neurons.

Local control and toxicity outcomes in brainstem metastases treated with single fraction radiosurgery: is there a volume threshold for toxicity?

Gamma Knife Radiosurgery (GKRS) has been reported in the treatment of brainstem metastases while dose volume toxicity thresholds remain mostly undefined. A retrospective review of 52 brainstem metastases in 44 patients treated with GKRS was completed. A median dose of 18 Gy (range 10-22 Gy) was prescribed to the tumor margin (median 50 % isodose). 25 patients had undergone previous whole brain radiation therapy. Toxicity was graded by the LENT-SOMA scale. Mean and median follow-up was 10 and 6 months. Only 3 of the 44 patients are living. Multiple brain metastases were treated in 75 % of patients. Median size of lesions was 0.134 cc, (range 0.013-6.600 cc). Overall survival rate at 1 year was 32 % (95 % CI 51.0-20.1 %) with a median survival time of 6 months (95 % CI 5.0-16.5). Local control rate at 6 months and 1 year was 88 % (95 % CI 70-95 %) and 74 % (95 % CI 52-87 %). Cause of death was neurologic in 17 patients, non-neurologic in 20 patients, and unknown in four. Four patients experienced treatment related toxicities. Univariate analysis of tumor volume revealed that volume greater than 1.0 cc predicted for toxicity. A strategy of using lower marginal doses with GKRS to brain stem metastases appears to lead to a lower local control rate than seen with lesions treated within the standard dose range in other locations. Tumor size greater than 1.0 cc predicted for treatment-related toxicity.

Breast cancer subtype affects patterns of failure of brain metastases after treatment with stereotactic radiosurgery.

We investigate the variance in patterns of failure after Gamma Knife™ radiosurgery (GKRS) for patients with brain metastases based on the subtype of the primary breast cancer. Between 2000 and 2010, 154 breast cancer patients were treated with GKRS for brain metastases. Tumor subtypes were approximated based on hormone receptor (HR) and HER2 status of the primary cancer: Luminal A/B (HR+/HER2(-)); HER2 (HER2+/HR(-)); Luminal HER2 (HR+/HER2+), Basal (HR(-)/HER2(-)), and then based on HER2 status alone. The median follow-up period was 54 months. Kaplan-Meier method was used to estimate survival times. Multivariable analysis was performed using Cox regression models. Median number of lesions treated was two (range 1-15) with a median dose of 20 Gy (range 9-24 Gy). Median overall survival (OS) was 7, 9, 11 and 22 months for Basal, Luminal A/B, HER2, and Luminal HER2, respectively (p = 0.001), and was 17 and 8 months for HER2+ and HER(-) patients, respectively (p < 0.001). Breast cancer subtype did not predict time to local failure (p = 0.554), but did predict distant brain failure rate (76, 47, 47, 36 % at 1 year for Basal, Luminal A/B, HER2, and Luminal HER2 respectively, p < 0.001). An increased proportion of HER2+ patients experienced neurologic death (46 vs 31 %, p = 0.066). Multivariate analysis revealed that HER2+ patients (p = 0.007) independently predicted for improved survival. Women with basal subtype have high rates of distant brain failure and worsened survival. Our data suggest that differences in biologic behavior of brain metastasis occur across breast cancer subtypes.

Patterns of failure after treatment of atypical meningioma with gamma knife radiosurgery.

Atypical meningiomas have poor local control with emerging literature indicating the use of radiosurgery in treatment. The purpose of this study was to evaluate clinical outcomes including local control and failure pattern after Gamma Knife radiosurgery (GKRS) and factors that may affect these outcomes. Between 1999 and 2008, 24 patients were treated with GKRS as either primary or salvage treatment for pathologically proven atypical meningiomas. Treatment failures were determined by serial magnetic resonance imaging. A median marginal dose of 14 Gy was used (range 10.5-18 Gy). Overall local control rates at 1, 2, and 5 years were 75, 51, and 44%, respectively. With median follow-up time of 42.5 months, 14 of 24 patients experienced a treatment failure at time of last follow-up. Eight recurrences were in-field, four were marginal failures, and two were distant failures. Wilcoxon analysis revealed that the conformality index (CI) was a significant predictor of local recurrence (P = 0.04). CI did not predict for distant recurrences (P = 0.16). On multivariate analysis evaluating factors predicting progression free survival, dose >14 Gy was found to be statistically significant (P = 0.01). There appears to be a dose response using GKRS beyond 14 Gy but given the suboptimal local control rates in this study, higher doses may still be needed to obtain better local control.

A phase II trial of thalidomide and procarbazine in adult patients with recurrent or progressive malignant gliomas.

Thalidomide and procarbazine have demonstrated single agent activity against malignant gliomas (MG). We evaluated the combination of thalidomide and procarbazine with a single arm phase II trial in adults with recurrent or progressive MG. Procarbazine was given at a dose of 250 mg/m(2)/d × 5day q 28 days. Thalidomide was administered at a dose of 200 mg/day continuously. Intrapatient dose escalation of thalidomide was attempted (increase by 100 mg/day weekly as tolerated) to a maximum of 800 mg/day. The primary outcome was tumor response, assessed by MRI and CT. Secondary outcomes were progression free survival (PFS), overall survival (OS) and toxicity. In addition, quality of life questionnaires were performed at baseline and prior to each odd cycle in all treated patients. Eighteen patients (median age of 50) were accrued and received a total of 36 cycles (median 2) of therapy. The median maximum thalidomide dose achieved was 400 mg (range 0-800). No complete or partial responses were seen. One patient (6%) experienced stable disease, fourteen (78%) progressed as best response and three (17%) were not evaluable for response. Median time to progression was 2.1 months (95% CI, 1.5-2.5). Seventeen patients have died (one patient lost to follow-up after progression); median survival from enrollment was 7.6 months (95% CI, 3.5-9.4). Grade 3/4 drug related toxicity was minimal. Quality of life diminished over time. The combination of thalidomide and procarbazine demonstrated no efficacy in this trial.

Gamma knife stereotactic radiosurgery for radiation-induced meningiomas.

BACKGROUND: Radiation-induced meningiomas present a unique clinical dilemma given the fact that patients with these tumors have often received a prior full course of radiotherapy. As such, traditional radiotherapy is limited by lifetime tissue tolerances to radiation, leaving surgery and radiosurgery as attractive treatment options. OBJECTIVES: To ascertain the safety and efficacy of Gamma Knife radiosurgery as a treatment for radiation-induced meningiomas. METHODS: A retrospective chart review was conducted to identify patients who received Gamma Knife radiosurgery for a meningioma and met the criteria for this being a radiation-induced tumor. Serial imaging was used to determine the outcome of treatment and clinical notes used to assess for toxicity. RESULTS: We present our series of 12 patients with radiation-induced meningiomas treated with Gamma Knife stereotactic radiosurgery over a 12-year period at our institution. With a median follow-up of 35 months, local control was 100%. Two patients experienced distant brain failure (>2 cm from previous radiosurgical volume). Two patients experienced posttreatment toxicity related to treatment-related edema. A review of data collected from the scientific literature suggests that tumor volume predicts for treatment failure of radiosurgery. CONCLUSIONS: Gamma Knife radiosurgery is both a safe and effective treatment for radiation-induced meningiomas.

Gamma knife radiosurgery in the treatment of tumor-related facial pain.

BACKGROUND: Intracranial neoplasms can cause pain similar to trigeminal neuralgia. Literature regarding radiosurgery for this is limited. We present a retrospective review of patients with tumor-related facial pain from benign lesions treated with gamma knife radiosurgery (GKRS) at Wake Forest University. OBJECTIVES: The primary objectives were to determine long-term pain relief and predictive factors for pain alleviation. METHODS: We reviewed 515 patients treated with GKRS for benign meningioma, vestibular schwannoma or trigeminal schwannoma between August 1999 and August 2010. Twenty-one eligible patients had tumor-related facial pain prior to GKRS. The median marginal tumor dose was 12 Gy. Long-term pain relief data were obtained by chart review and telephone interview. RESULTS: The median follow-up for symptom evaluation was 3.8 years. Seventeen of 21 patients (81%) experienced a Barrow Neurological Institute (BNI) score of I-III at 6 months following GKRS. Kaplan-Meier estimates of freedom from BNI IV-V relapse were 66% at 1 year and 53% at 2 years. No pain relapses occurred after 2 years. CONCLUSION: GKRS of benign lesions is a noninvasive option for patients with tumor-related facial pain. Pain relief is modest, with the majority of pain relapses occurring within 2 years and approximately one half of patients maintaining relief beyond 2 years.

A parametric study delineating irreversible electroporation from thermal damage based on a minimally invasive intracranial procedure.

BACKGROUND: Irreversible electroporation (IRE) is a new minimally invasive technique to kill undesirable tissue in a non-thermal manner. In order to maximize the benefits from an IRE procedure, the pulse parameters and electrode configuration must be optimized to achieve complete coverage of the targeted tissue while preventing thermal damage due to excessive Joule heating. METHODS: We developed numerical simulations of typical protocols based on a previously published computed tomographic (CT) guided in vivo procedure. These models were adapted to assess the effects of temperature, electroporation, pulse duration, and repetition rate on the volumes of tissue undergoing IRE alone or in superposition with thermal damage. RESULTS: Nine different combinations of voltage and pulse frequency were investigated, five of which resulted in IRE alone while four produced IRE in superposition with thermal damage. CONCLUSIONS: The parametric study evaluated the influence of pulse frequency and applied voltage on treatment volumes, and refined a proposed method to delineate IRE from thermal damage. We confirm that determining an IRE treatment protocol requires incorporating all the physical effects of electroporation, and that these effects may have significant implications in treatment planning and outcome assessment. The goal of the manuscript is to provide the reader with the numerical methods to assess multiple-pulse electroporation treatment protocols in order to isolate IRE from thermal damage and capitalize on the benefits of a non-thermal mode of tissue ablation.

Staged gamma knife radiosurgery for large cerebral arteriovenous malformations.

BACKGROUND: We present our experience over a 10-year period of staged radiosurgery for large arteriovenous malformations (AVMs) including patient outcomes and methods. METHODS: From July 2000 to December 2010, 80 patients with AVMs were treated with gamma knife radiosurgery (GKS) at our institution; of these patients, 5 were treated for large AVMs with staged GKS (volumes >20 cm(3)). The mean interval between treatments was 10 months (range 7-16). The mean dose for the margin used was 18.0 Gy (range 16-20). The mean volume treated was 37.2 cm(3) (range 22-50). The mean total follow-up was 76.5 months (range 42-120). RESULTS: Two patients had complete obliteration of the AVM nidus. One patient had 95% obliteration (31 months after radiosurgery), one had 90% obliteration (38 months after radiosurgery), and one had less than 50% obliteration at 53 months with a 16-month interval between staged treatments. CONCLUSIONS: Staged radiosurgery is an effective and safe method for the treatment of large AVMs. We report achieving higher marginal doses with staging in planned intervals of 6-9 months between staged treatments. It appears that the longer the wait between treatments, the less likely it is that complete obliteration will be achieved.

Intracranial nonthermal irreversible electroporation: in vivo analysis.

Nonthermal irreversible electroporation (NTIRE) is a new minimally invasive technique to treat cancer. It is unique because of its nonthermal mechanism of tumor ablation. Intracranial NTIRE procedures involve placing electrodes into the targeted area of the brain and delivering a series of short but intense electric pulses. The electric pulses induce irreversible structural changes in cell membranes, leading to cell death. We correlated NTIRE lesion volumes in normal brain tissue with electric field distributions from comprehensive numerical models. The electrical conductivity of brain tissue was extrapolated from the measured in vivo data and the numerical models. Using this, we present results on the electric field threshold necessary to induce NTIRE lesions (495-510 V/cm) in canine brain tissue using 90 50-mus pulses at 4 Hz. Furthermore, this preliminary study provides some of the necessary numerical tools for using NTIRE as a brain cancer treatment. We also computed the electrical conductivity of brain tissue from the in vivo data (0.12-0.30 S/m) and provide guidelines for treatment planning and execution. Knowledge of the dynamic electrical conductivity of the tissue and electric field that correlates to lesion volume is crucial to ensure predictable complete NTIRE treatment while minimizing damage to surrounding healthy tissue.

Deep brain stimulation for medically refractory epilepsy.

Epilepsy is a chronic neurological disorder that affects 0.5-1% of the population. Up to one-third of patients will have incompletely controlled seizures or debilitating side effects of anticonvulsant medications. Although some of these patients may be candidates for resection, many are not. The desire to find alternative treatments for epilepsy has led to a resurgence of interest in the use of deep brain stimulation (DBS), which has been used quite successfully in movement disorders. Small pilot studies and open-label trials have yielded results that may support the use of DBS in selected patients with refractory seizures. Because of the diversity of regions involved with seizure initiation and propagation, a variety of targets for stimulation have been examined. Moreover, stimulation parameters such as amplitude, frequency, pulse duration, and continuous versus intermittent on vary from one study to the next. More studies are necessary to determine if there is an appropriate population of seizure patients for DBS, the optimal target, and the most efficacious stimulation parameters.

The Protective Action Encoding of Serotonin Transients in the Human Brain.

The role of serotonin in human brain function remains elusive due, at least in part, to our inability to measure rapidly the local concentration of this neurotransmitter. We used fast-scan cyclic voltammetry to infer serotonergic signaling from the striatum of 14 brains of human patients with Parkinson's disease. Here we report these novel measurements and show that they correlate with outcomes and decisions in a sequential investment game. We find that serotonergic concentrations transiently increase as a whole following negative reward prediction errors, while reversing when counterfactual losses predominate. This provides initial evidence that the serotonergic system acts as an opponent to dopamine signaling, as anticipated by theoretical models. Serotonin transients on one trial were also associated with actions on the next trial in a manner that correlated with decreased exposure to poor outcomes. Thus, the fluctuations observed for serotonin appear to correlate with the inhibition of over-reactions and promote persistence of ongoing strategies in the face of short-term environmental changes. Together these findings elucidate a role for serotonin in the striatum, suggesting it encodes a protective action strategy that mitigates risk and modulates choice selection particularly following negative environmental events.

Reducing set-up uncertainty in the Elekta Stereotactic Body Frame using Stealthstation software.

The Elekta Stereotactic Body Frame (SBF) is a device which allows extracranial targets to be localized and irradiated in a stereotactic coordinate system. Errors of positioning of the body relative to the frame are indirectly estimated by image fusion of multiple CT scans. A novel repositioning methodology, based on neurosurgical Stealth technology, is presented whereby accurate patient repositioning is directly confirmed before treatment delivery. Repositioning was performed on four extracranial stereotactic radiosurgery patients and a radiotherapy simulation phantom. The setup error was quantitatively measured by fiducial localization. A confirmatory CT scan was performed and the resulting image set registered to the initial scan to quantify shifts in the GTV isocenter. Alignment confirmation using Stealth took between 5 and 10 minutes. For the phantom studies, a reproducibly of 0.6 mm accuracy of phantom-to-SBF alignment was measured. The results on four actual patients showed setup errors of 1.5 mm or less. Using the Stealth Station process, rapid confirmation of alignment on the treatment table is possible.

Does dose rate affect efficacy? The outcomes of 256 gamma knife surgery procedures for trigeminal neuralgia and other types of facial pain as they relate to the half-life of cobalt.

OBJECT: Gamma Knife surgery (GKS) is a treatment option for patients with refractory typical trigeminal neuralgia (TN), TN with atypical features, and atypical types of facial pain. The Gamma Knife's 201 60Co sources decay with a half-life of 5.26 years. The authors examined whether the decrease in dose rate over 4.6 years between Co source replacements affected the control rates of facial pain in patients undergoing GKS. METHODS: The authors collected complete follow-up data on 239 of 326 GKS procedures performed in patients with facial pain. Patients were classified by their type of pain. The isocenter of a 4-mm collimator helmet was targeted at the proximal trigeminal nerve root, and the dose (80-90 Gy) was prescribed at the 100% isodose line. Patients reported the amount of pain control following radiosurgery by answering a standardized questionnaire. Eighty percent of patients experienced greater than 50% pain relief, and 56% of patients experienced complete pain relief after GKS. Neither dose rate nor treatment time was significantly associated with either the control rate or degree of pain relief. A significant association between the type of facial pain and the pain control rate after GKS was observed (p < 0.001; Pearson chi-square test). In their statistical analysis, the authors accounted for changes in prescription dose over time to prevent the dose rate from being a confounding variable. There was no observable effect of the dose rate or of the treatment duration within the typical period to source replacement. CONCLUSIONS: Patients with facial pain appear to receive consistent treatment with GKS at any time during the first half-life of the Co sources.

Results of a phase II trial of the GliaSite radiation therapy system for the treatment of newly diagnosed, resected single brain metastases.

OBJECT: The aim of this study was to evaluate the effectiveness of brachytherapy using the GliaSite Radiation Therapy System in patients with a newly diagnosed resected single brain metastasis. The primary end point of the study was local tumor control. The secondary end points included patient survival, distant brain recurrence, quality of life, and treatment toxicity. METHODS: The authors conducted a prospective multiinstitutional phase II study of GliaSite brachytherapy prescribed at a 60-Gy dose administered to a 1-cm depth after resection of a single brain metastasis. No whole-brain radiation therapy was given. Patients were assessed at 1 and 3 months after brachytherapy and every 3 months thereafter for up to 2 years. Seventy-one patients were enrolled at 13 centers. A GliaSite balloon catheter was implanted in 62 patients. Fifty-four patients received brachytherapy. The median patient age was 60 years. The most common tumor (54%) was non-small cell lung cancer. Fifty-seven percent of patients had brain metastasis only, whereas 43% had extracranial metastasis. The median final administered dose was 60 Gy. The magnetic resonance imaging--determined local control rate, based on several different methods, was 82 to 87%. Both the median patient survival time and the median duration of functional independence were 40 weeks. Among the 35 patients who died, the cause of death was neurological in 11%. Thirteen patients underwent reoperation for suspected tumor recurrence or radiation necrosis, and histological diagnoses included radiation necrosis without tumor (nine patients), radiation necrosis mixed with tumor (two patients), and tumor only (two patients). Extracranial metastasis, tumor size, and radiation necrosis were significant factors affecting patient survival. CONCLUSIONS: In patients with a resected single brain metastasis, GliaSite brachytherapy leads to a local control rate, median patient survival time, and duration of functional independence similar to those achieved with resection plus whole-brain radiation therapy.

Gamma Knife surgery targeting the resection cavity of brain metastasis that has progressed after whole-brain radiotherapy.

OBJECT: Salvage treatment of large, symptomatic brain metastases after failure of whole-brain radiotherapy (WBRT) remains challenging. When these lesions require resection, there are few options to lower expected rates of local recurrence at the resection cavity margin. The authors describe their experience in using Gamma Knife surgery (GKS) to target the resection cavity in patients whose tumors had progressed after WBRT. METHODS: The authors retrospectively identified 143 patients in whom GKS had been used to target a brain metastasis resection cavity between 2000 and 2005. Seventy-nine of these patients had undergone WBRT prior to resection and GKS. The median patient age was 53 years, and the median prescribed dose was 18 Gy (range 8-24 Gy), with resection cavities of relatively larger volume (> 15 cm3). The GKS dose was prescribed at the 40 to 95% isodose contour (mode 50%). Local recurrence within 1 cm of the treatment volume occurred in four (5.1%) of 79 cases. The median duration of time to local recurrence was 6.1 months (range 2-13 months). The median duration of time to occurrence of distant metastases following GKS of the resection cavity was 10.8 months (range 2-86 months). Carcinomatous meningitis developed in four (5.1%) of 79 cases. Symptomatic radionecrosis requiring surgical treatment occurred in three (3.8%) of 79 cases. The median duration of survival following GKS of the resection cavity was 69.6 weeks. The median 2- and 5-year survival rates were 20.2 and 6.3%, respectively. CONCLUSIONS: When metastases progress after WBRT and require resection, GKS targeting the resection cavity is a viable strategy. In 75 (94.9%) of 79 cases, GKS of the resection cavity in patients in whom WBRT had failed appears to have achieved its goal of local disease control.

Glossopharyngeal neuralgia treated with gamma knife surgery: treatment outcome and failure analysis. Case report.

Glossopharyngeal neuralgia (GPN) is a rare condition in which patients present with intractable deep throat pain. Similar to trigeminal neuralgia (TN), treatment with microvascular decompression (MVD) has been successful in both. Because gamma knife surgery (GKS) has also been shown to be effective in treating TN, it seemed reasonable to apply it to GPN. The authors present the first report of GKS-treated GPN in a patient who presented with severe, poorly controlled GPN and who refused MVD.

Safety and feasibility of the NanoKnife system for irreversible electroporation ablative treatment of canine spontaneous intracranial gliomas.

OBJECT: Irreversible electroporation (IRE) is a novel nonthermal ablation technique that has been used for the treatment of solid cancers. However, it has not been evaluated for use in brain tumors. Here, the authors report on the safety and feasibility of using the NanoKnife IRE system for the treatment of spontaneous intracranial gliomas in dogs. METHODS: Client-owned dogs with a telencephalic glioma shown on MRI were eligible. Dog-specific treatment plans were generated by using MRI-based tissue segmentation, volumetric meshing, and finite element modeling. After biopsy confirmation of glioma, IRE treatment was delivered stereotactically with the NanoKnife system using pulse parameters and electrode configurations derived from therapeutic plans. The primary end point was an evaluation of safety over the 14 days immediately after treatment. Follow-up was continued for 12 months or until death with serial physical, neurological, laboratory, and MRI examinations. RESULTS: Seven dogs with glioma were treated. The mean age of the dogs was 9.3 ± 1.6 years, and the mean pretreatment tumor volume was 1.9 ± 1.4 cm(3). The median preoperative Karnofsky Performance Scale score was 70 (range 30-75). Severe posttreatment toxicity was observed in 2 of the 7 dogs; one developed fatal (Grade 5) aspiration pneumonia, and the other developed treatment-associated cerebral edema, which resulted in transient neurological deterioration. Results of posttreatment diagnostic imaging, tumor biopsies, and neurological examinations indicated that tumor ablation was achieved without significant direct neurotoxicity in 6 of the 7 dogs. The median 14-day post-IRE Karnofsky Performance Scale score of the 6 dogs that survived to discharge was 80 (range 60-90), and this score was improved over the pretreatment value in every case. Objective tumor responses were seen in 4 (80%) of 5 dogs with quantifiable target lesions. The median survival was 119 days (range 1 to > 940 days). CONCLUSION: With the incorporation of additional therapeutic planning procedures, the NanoKnife system is a novel technology capable of controlled IRE ablation of telencephalic gliomas.

Current controversies in the radiotherapeutic management of adult low-grade glioma.

Over the last decade, the results of four prospective clinical trials of supratentorial low-grade glioma (LGG) in adults have been published. The data from the nearly 1,000 patients treated on these studies are summarized in this presentation, addressing the following three current controversies in the radiotherapeutic management of these patients: (1) optimum timing of radiation therapy (RT); (2) optimum RT dose; and (3) addition of chemotherapy to RT. The 5-year overall survival (OS) and progression-free survival (PFS) rates in these four studies ranged from 58% to 72% and from 37% to 55%, respectively. Significant prognostic factors included extent of surgical resection, histology, tumor size, and age. The European Organization for Research and Treatment of Cancer (EORTC) study 22845 randomized 311 adults to postoperative observation or RT. There was no difference in the 5-year OS rate between the two arms, but the irradiated patients had a significantly improved 5-year PFS rate. EORTC study 22844 randomized 379 adults to low- versus high-dose RT. Similarly, an intergroup study conducted by the North Central Cancer Treatment Group (NCCTG), Radiation Therapy Oncology Group (RTOG), and Eastern Cooperative Group (ECOG) randomized 211 adults to low- versus high-dose RT. There was no difference in the 5-year OS or PFS rates between the two dose groups in either study. A Southwest Oncology Group (SWOG) study randomized 60 adults with incompletely resected LGG to RT alone or RT plus lomustine (CCNU) chemotherapy. There was no difference in outcome between the two treatment arms. Further prospective clinical trials are needed to define the optimal management strategy for adults with supratentorial LGG. The schemata from recently completed and ongoing LGG studies will be presented.