Laser interstitial thermal therapy for deep-seated perivascular brain tumors is not associated with distal ischemia

PURPOSE

Laser interstitial thermal therapy (LITT) is a minimally invasive cytoreductive treatment option for brain tumors with a risk of vascular injury from catheter placement or thermal energy. This may be of concern with deep-seated tumors that have surrounding end-artery perforators and critical microvasculature. The purpose of this study was to assess the risk of distal ischemia following LITT for deep-seated perivascular brain tumors.

METHODS

A retrospective review of a multi-institution database was used to identify patients who underwent LITT between 2013 and 2022 for tumors located within the insula, thalamus, basal ganglia, and anterior perforated substance. Demographic, clinical and volumetric tumor characteristics were collected. The primary outcome was radiographic evidence of distal ischemia on post-ablation magnetic resonance imaging (MRI).

RESULTS

61 LITT ablations for deep-seated perivascular brain tumors were performed. Of the tumors treated, 24 (39%) were low-grade gliomas, 32 (52%) were high-grade gliomas, and 5 (8%) were metastatic. The principal location included 31 (51%) insular, 14 (23%) thalamic, 13 (21%) basal ganglia, and 3 (5%) anterior perforated substance tumors. The average tumor size was 19.6 cm3 with a mean ablation volume of 11.1 cm3. The median extent of ablation was 92% (IQR 30%, 100%). Two patients developed symptomatic intracerebral hemorrhage after LITT. No patient had radiographic evidence of distal ischemia on post-operative diffusion weighted imaging.

CONCLUSION

We demonstrate that LITT for deep-seated perivascular brain tumors has minimal ischemic risks and is a feasible cytoreductive treatment option for otherwise difficult to access intracranial tumors.

Detection of diagnostic and prognostic methylation-based signatures in liquid biopsy specimens from patients with meningiomas

Recurrence of meningiomas is unpredictable by current invasive methods based on surgically removed specimens. Identification of patients likely to recur using noninvasive approaches could inform treatment strategy, whether intervention or monitoring. In this study, we analyze the DNA methylation levels in blood (serum and plasma) and tissue samples from 155 meningioma patients, compared to other central nervous system tumor and non-tumor entities. We discover DNA methylation markers unique to meningiomas and use artificial intelligence to create accurate and universal models for identifying and predicting meningioma recurrence, using either blood or tissue samples. Here we show that liquid biopsy is a potential noninvasive and reliable tool for diagnosing and predicting outcomes in meningioma patients. This approach can improve personalized management strategies for these patients.

Laser Interstitial Thermal Therapy for First-Line Treatment of Surgically Accessible Recurrent Glioblastoma: Outcomes Compared With a Surgical Cohort

BACKGROUND

Laser interstitial thermal therapy (LITT) for glioblastoma (GBM) has been reserved for poor surgical candidates and deep "inoperable" lesions. We present the first reported series of LITT for surgically accessible recurrent GBM (rGBM) that would otherwise be treated with surgical resection.

OBJECTIVE

To evaluate the use of LITT for unifocal, lobar, first-time rGBM compared with a similar surgical cohort.

METHODS

A retrospective institutional database was used to identify patients with unifocal, lobar, first-time rGBM who underwent LITT or resection between 2013 and 2020. Clinical and volumetric lesional characteristics were compared between cohorts. Subgroup analysis of patients with lesions ≤20 cm 3 was also completed. Primary outcomes were overall survival and progression-free survival.

RESULTS

Of the 744 patients with rGBM treated from 2013 to 2020, a LITT cohort of 17 patients were compared with 23 similar surgical patients. There were no differences in baseline characteristics, although lesions were larger in the surgical cohort (7.54 vs 4.37 cm 3 , P = .017). Despite differences in lesion size, both cohorts had similar extents of ablation/resection (90.7% vs 95.1%, P = .739). Overall survival (14.1 vs 13.8 months, P = .578) and progression-free survival (3.7 vs 3.3 months, P = 0. 495) were similar. LITT patients had significantly shorter hospital stays (2.2 vs 3.0 days, P = .004). Subgroup analysis of patients with lesions ≤20 cm 3 showed similar outcomes, with LITT allowing for significantly shorter hospital stays.

CONCLUSION

We found no difference in survival outcomes or morbidity between LITT and repeat surgery for surgically accessible rGBM while LITT resulted in shorter hospital stays and more efficient postoperative care.

Hypertrophic olivary degeneration and palatal myoclonus from a Streptococcus intermedius infection of the brain: illustrative case

BACKGROUND

Hypertrophic olivary degeneration (HOD) is a rare condition that can occur after disruption of the Guillain-Mollaret triangle. Clinically, HOD can present with palatal myoclonus with or without oculopalatal tremor, which sometimes results in symptomatic dysphagia and/or speech abnormalities. This condition is commonly associated with vascular lesions, with only three prior reported cases of HOD resulting from intracranial abscess.

OBSERVATIONS

An otherwise healthy patient developed multiple intracranial abscesses. Biopsy showed gram-positive cocci; however, culture findings were negative. Polymerase chain reaction (PCR) identified Streptococcus intermedius. The patient demonstrated palatal myoclonus and vertical nystagmus, which resulted in persistent mild dysphagia and altered speech intonation. After appropriate antimicrobial therapy with resolution of the enhancing lesions, symptoms persisted. Follow-up imaging demonstrated progressive hypertrophy of the right olive with persistent disruption of the right-sided rubro-olivo fiber pathways.

LESSONS

Although HOD classically occurs after vascular insult, it can also be seen as a postinfectious sequela. Despite eradication of the infection, palatal myoclonus and oculopalatal tremor may have a persistent impact on quality of life due to impaired speech and swallowing. This case emphasizes the utility of universal PCR in detecting fastidious organisms as well as diffusion tensor imaging for characterization of disrupted fiber pathways.

Clinically useful tumor fluorescence greater than 24 hours after 5-aminolevulinic acid administration

Background:

5-aminolevulinic acid (5-ALA) is a valuable surgical adjuvant used for the resection of glioblastoma multiforme (GBM). Since Food and Drug Administration approval in 2017, 5-ALA has been used in over 37,000 cases. The current recommendation for peak efficacy and intraoperative fluorescence is within 4 h after administration. This narrow time window imposes a perioperative time constraint which may complicate or preclude the use of 5-ALA in GBM surgery.

Case Description:

This case report describes the prolonged activity of 5-ALA in a 66-year-old patient with a newly diagnosed GBM lesion within the left supramarginal gyrus. An awake craniotomy with language and sensorimotor mapping was planned along with 5-ALA fluorescence guidance. Shortly, after receiving the preoperative 5-ALA dose, the patient developed a fever. Surgery was postponed for an infectious disease workup which proved negative. The patient was taken to surgery the following day, 36 h after 5-ALA administration. Despite the delay, intraoperative fluorescence within the tumor remained and was sufficient to guide resection. Postoperative imaging confirmed a gross total resection of the tumor.

Conclusion:

The use of 5-ALA as an intraoperative adjuvant may still be effective for patients beyond the recommended 4-h window after initial administration. Reconsideration of current use of 5-ALA is warranted.

Detection of Tumor-specific DNA Methylation Markers in the Blood of Patients with Pituitary Neuroendocrine Tumors

Background

DNA methylation abnormalities are pervasive in pituitary neuroendocrine tumors (PitNETs). The feasibility to detect methylome alterations in circulating cell-free DNA (cfDNA) has been reported for several central nervous system (CNS) tumors but not across PitNETs. The aim of the study was to use the liquid biopsy (LB) approach to detect PitNET-specific methylation signatures to differentiate these tumors from other sellar diseases.

Methods

We profiled the cfDNA methylome (EPIC array) of 59 serum and 41 plasma LB specimens from patients with PitNETs and other CNS diseases (sellar tumors and other pituitary non-neoplastic diseases, lower-grade gliomas, and skull-base meningiomas) or nontumor conditions, grouped as non-PitNET.

Results

Our results indicated that despite quantitative and qualitative differences between serum and plasma cfDNA composition, both sources of LB showed that patients with PitNETs presented a distinct methylome landscape compared to non-PitNETs. In addition, LB methylomes captured epigenetic features reported in PitNET tissue and provided information about cell-type composition. Using LB-derived PitNETs-specific signatures as input to develop machine-learning predictive models, we generated scores that distinguished PitNETs from non-PitNETs conditions, including sellar tumor and non-neoplastic pituitary diseases, with accuracies above ~93% in independent cohort sets.

Conclusions

Our results underpin the potential application of methylation-based LB profiling as a noninvasive approach to identify clinically relevant epigenetic markers to diagnose and potentially impact the prognostication and management of patients with PitNETs.

Sinonasal Packing is Not a Requisite for Successful Cerebrospinal Fluid Leak Repair

Background Numerous methods have been described to repair nasal cerebrospinal fluid (CSF) leaks. Most studies have focused on optimizing CSF leak repair success, leading to closure rates of 90 to 95%.

Objective This study aimed to determine if excellent reconstruction rates could be achieved without using sinonasal packing.

Methods A prospective case series of 73 consecutive patients with various CSF leak etiologies and skull base defects was conducted to evaluate reconstruction success without sinonasal packing. The primary outcome measure was postoperative CSF leak. Secondary outcome measures were postoperative epistaxis requiring intervention in operating room or emergency department, infectious sinusitis, and 22-item sinonasal outcome test (SNOT-22) changes.

Results Mean age was 54.5 years and 64% were female. Multilayered reconstructions were performed in 55.3% of cases, with collagen or bone epidural inlay grafts, and nasal mucosal grafts or nasoseptal flaps for onlay layers. Onlay-only reconstructions with mucosal grafts or nasoseptal flaps were performed in 44.7% of cases. Tissue sealants were used in all cases, and lumbar drains were used in 40.8% of cases. There were two initial failures (97.4% initial success), but both resolved with lumbar drains alone (no revision surgeries). There were no instances of postoperative epistaxis requiring intervention in the operating room or emergency department. Infectious sinusitis occurred in 2.7% of patients in the first 3 months postoperatively. SNOT-22 did not change significantly from preoperatively to first postoperative visits, then improved over time.

Conclusion Nasal CSF leaks from various etiologies and defect sites were successfully repaired without using sinonasal packing, and patients experienced minimal sinonasal morbidity.

Reducing Superfluous Opioid Prescribing Practices After Brain Surgery: It Is Time to Talk About Drugs

BACKGROUND

Opioids are prescribed routinely after cranial surgery despite a paucity of evidence regarding the optimal quantity needed. Overprescribing may adversely contribute to opioid abuse, chronic use, and diversion.

OBJECTIVE

To evaluate the effectiveness of a system-wide campaign to reduce opioid prescribing excess while maintaining adequate analgesia.

METHODS

A retrospective cohort study of patients undergoing a craniotomy for tumor resection with home disposition before and after a 2-mo educational intervention was completed. The educational initiative was composed of directed didactic seminars targeting senior staff, residents, and advanced practice providers. Opioid prescribing patterns were then assessed for patients discharged before and after the intervention period.

RESULTS

A total of 203 patients were discharged home following a craniotomy for tumor resection during the study period: 98 who underwent surgery prior to the educational interventions compared to 105 patients treated post-intervention. Following a 2-mo educational period, the quantity of opioids prescribed decreased by 52% (median morphine milligram equivalent per day [interquartile range], 32.1 [16.1, 64.3] vs 15.4 [0, 32.9], P < .001). Refill requests also decreased by 56% (17% vs 8%, P = .027) despite both groups having similar baseline characteristics. There was no increase in pain scores at outpatient follow-up (1.23 vs 0.85, P = .105).

CONCLUSION

A dramatic reduction in opioids prescribed was achieved without affecting refill requests, patient satisfaction, or perceived analgesia. The use of targeted didactic education to safely improve opioid prescribing following intracranial surgery uniquely highlights the ability of simple, evidence-based interventions to impact clinical decision making, lessen potential patient harm, and address national public health concerns.

Fluorescence-Guided High-Grade Glioma Surgery More Than Four Hours After 5-Aminolevulinic Acid Administration

Background: Fluorescence-guided surgery (FGS) using 5-aminolevulic acid (5-ALA) is a widely used strategy for delineating tumor tissue from surrounding brain intraoperatively during high-grade glioma (HGG) resection. 5-ALA reaches peak plasma levels ~4 h after oral administration and is currently approved by the FDA for use 2–4 h prior to induction to anesthesia.

Objective: To demonstrate that there is adequate intraoperative fluorescence in cases undergoing surgery more than 4 h after 5-ALA administration and compare survival and radiological recurrence to previous data.

Methods: Retrospective analysis of HGG patients undergoing FGS more than 4 h after 5-ALA administration was performed at two institutions. Clinical, operative, and radiographic pre- and post-operative characteristics are presented.

Results: Sixteen patients were identified, 6 of them female (37.5%), with mean (SD) age of 59.3 ± 11.5 years. Preoperative mean modified Rankin score (mRS) was 2 ± 1. All patients were dosed with 20 mg/kg 5-ALA the morning of surgery. Mean time to anesthesia induction was 425 ± 334 min. All cases had adequate intraoperative fluorescence. Eloquent cortex was involved in 12 cases (75%), and 13 cases (81.3%) had residual contrast enhancement on postoperative MRI. Mean progression-free survival was 5 ± 3 months. In the study period, 6 patients died (37.5%), mean mRS was 2.3 ± 1.3, Karnofsky score 71.9 ± 22.1, and NIHSS 3.9 ± 2.4.

Conclusion: Here we demonstrate that 5-ALA-guided HGG resection can be performed safely more than 4 h after administration, with clinical results largely similar to previous reports. Relaxation of timing restrictions could improve procedure workflow in busy neurosurgical centers, without additional risk to patients.

Minimally Invasive Surgery Strategies: Changing the Treatment of Spine Tumors

Innovation in surgical technique and contemporary spinal instrumentation paired with intraoperative navigation/imaging concepts allows for safer and less-invasive surgical approaches. The combination of stereotactic body radiotherapy, contemporary surgical adjuncts, and less-invasive techniques serves to minimize blood loss, soft tissue injury, and length of hospital stay without compromising surgical efficacy, potentially enabling patients to begin adjuvant treatment sooner.

Adapting to Space Limitations During Prone Real-Time Magnetic Resonance Imaging-Guided Stereotaxic Laser Ablation: Technical Pearls

BACKGROUND

New techniques of intraoperative magnetic resonance imaging (MRI)-guided stereotaxy enable minimally invasive approaches to intracranial pathology. Laser interstitial thermal therapy (LITT), convection-enhanced drug delivery, and stereotactic biopsy can be performed with a real-time confirmation of location and the ability to adjust for intracranial shift during the procedure. However, these procedures are constrained by patient positioning and the need for trajectories that avoid collision between stereotactic elements and the small MRI bore. To our knowledge, this is the first report to outline the technical details of safe intraoperative MRI (iMRI)-guided stereotaxy, performed with prone positioning.

OBJECTIVE

To present technical pearls to guide the safe conduction of iMRI-guided stereotaxy and LITT while in the prone position.

METHODS

The details of the positioning and trajectories for a series of patients who underwent Clearpoint® (MRI Interventions Inc) frameless real-time MRI-guided stereotaxis using a posterior approach were reviewed.

RESULTS

In this series, 5 patients underwent selective amygdalohippocampectomy, and 2 underwent tumor biopsy/ablation while in the prone position without any complications.

CONCLUSION

Prone iMRI procedures can be performed safely even in a 60-cm MRI bore.

Trends in the Abscopal Effect After Radiation to Spinal Metastases: A Systematic Review

While the abscopal effect has been previously described, the phenomenon has been poorly defined in the case of spinal metastases. This article is unique in that we present the first systematic review of the abscopal effect after radiation therapy to metastatic spinal cancer, especially since the spinal column represents one of the most common metastatic locations. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in the Enhancing the QUAlity and Transparency Of health Research (EQUATOR) resources, a systematic review identified relevant studies via a computer-aided search of MEDLINE and Embase. Ten publications that met the inclusion and exclusion criteria from the PRISMA flow diagram described a total of 13 patients, 76.9% of whom demonstrated image findings of the abscopal effect. In summary, important trends in the nine patients who experienced the abscopal effect in this review include higher doses of radiation and treatment with immunomodulators, both of which may help guide treatment paradigms for spinal metastases superimposed on diffuse metastatic disease. These trends, however, still warrant further investigations with experimental and clinical studies for a mechanistic understanding of the abscopal effect.

Abstract LB-234: Pre-surgical identification of diagnostic, prognostic and predictive DNA methylation-based markers in serum (liquid biopsy) of patients harboring gliomas

Central nervous system-related tumors release tumoral material into circulating blood and the cerebrospinal fluid (e.g. cell free DNA). The sampling of these biofluids, i.e. liquid biopsy (LB), may offer an opportunity for diagnosis, prognostication and response prediction in a constantly evolving and biologically and prognostically heterogeneous tumor, such as glioma, in real-time. In glioma-tumor tissue, genome-wide DNA methylation profiling has shown that epigenetic abnormalities play significant biological and clinical roles, making DNA methylome profiling attractive for LB application in these tumors. Thus far, studies of epigenetic LB (eLB) focused on targeted markers which have shown low sensitivity; however, this can be potentially circumvented by a comprehensive genome-wide CpG methylation profiling. Herein, we profiled the genome-wide CpG methylation landscape of matching serum/tissue from 22 patients who received surgical resection for a glioma diagnosis (15 IDH-mutant and 7 IDH-wildtype) and 4 who received surgical resection of the brain for a non-tumor brain related disease. We identified 199 glioma specific DNA methylation-serum based markers (Wilcoxon Rank Sum test, p-value &lt; 0.001) that differentiated glioma from non-tumor brain tissues (diagnostic eLB). These eLB diagnostic markers were found to be enriched for CpG islands and depleted for open seas and shores. Interestingly, CpG methylation of MYC and CD34 promoters, previously described in the tissue, were detectable in the serum of glioma patients as part of the 199 CpG eLB signature. We also identified 987 eLB markers (Wilcoxon Rank Sum test, p-value &lt; 0.01) that discriminated patients with IDH-mutant from IDH-wildtype (prognostic eLB). Among the initial cohort, comprised by 4 MGMT-unmethylated and 18 MGMT-methylated gliomas, we also identified 428 specific eLB markers that discriminated the MGMT status among the patients (predictive eLB). Harnessing DNA methylation data of The Cancer Genome Atlas (TCGA) consortium, derived from 10,000 primary and untreated tumor tissue samples, spanning 33 cancer types, we found our three eLB signatures (diagnostic, prognostic and predictive) to be highly specific to gliomas. Our results suggest that serum eLB profiling may be useful as a surrogate or complementary for tissue-based approach for diagnosis, prognostication and treatment prediction of gliomas. In addition, our eLB signatures can be applied as a real-time non-invasive approach to improve detection of glioma progression and recurrence. Once validated, the application of the eLB panels discovered in this study have the potential to significantly and positively improve the pre- and post-surgical quality of care for patients harboring gliomas.

Citation Format: Houtan Noushmehr, Thais S. Sabedot, Tathiane M. Malta, Kevin K. Nelson, James Snyder, Michael Wells, Maritza S. Mosella, Ana C. deCarvalho, Karam Asmaro, Lisa Scarpace, Adam M. Robin, Mark L. Rosenblum, Tom Mikkelsen, Jack Rock, Tobias Walbert, Ian Lee, Laila M. Poisson, Steven N. Kalkanis, Ana V. Castro. Pre-surgical identification of diagnostic, prognostic and predictive DNA methylation-based markers in serum (liquid biopsy) of patients harboring gliomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-234.

Delirium and topographical disorientation associated with glioblastoma multiforme tumour progression into the isthmus of the cingulate gyrus

Since there is no cure for glioblastoma multiforme (GBM), the goal of treatment becomes prolonging the survival through cytoreduction while minimising neurological deficits. In this case report, laser interstitial thermal therapy (LITT) was used once the tumour progressed into the isthmus of the cingulate gyrus. One year after temporal lobectomy, disorders of memory, emotion, personality and navigation, likely related to limbic system involvement along with hallucinations and fluctuating cognition occurred as the tumour progressed. After ablation of the posterior cingulum, worsening of topographical disorientation was observed.Per literature review, delirium has been noted in patients with strokes involving the right-sided temporo-parieto-occipital junction, and topographical disorientation has been associated with lesions of the right posterior cingulum. Alternative causes of these deficits were ruled out, leaving structural changes as the primary explanation. This is the first report of the neurological deficits associated with tumour progression and vasogenic oedema in this region.

Complications of ventricular entry during craniotomy for brain tumor resection

OBJECTIVE Recent studies have demonstrated that periventricular tumor location is associated with poorer survival and that tumor location near the ventricle limits the extent of resection. This finding may relate to the perception that ventricular entry leads to further complications and thus surgeons may choose to perform less aggressive resection in these areas. However, there is little support for this view in the literature. This study seeks to determine whether ventricular entry is associated with more complications during craniotomy for brain tumor resection. METHODS A retrospective analysis of patients who underwent craniotomy for tumor resection at Henry Ford Hospital between January 2010 and November 2012 was conducted. A total of 183 cases were reviewed with attention to operative entry into the ventricular system, postoperative use of an external ventricular drain (EVD), subdural hematoma, hydrocephalus, and symptomatic intraventricular hemorrhage (IVH). RESULTS Patients in whom the ventricles were entered had significantly higher rates of any complication (46% vs 21%). Complications included development of subdural hygroma, subdural hematoma, intraventricular hemorrhage, subgaleal collection, wound infection, urinary tract infection/deep venous thrombosis, hydrocephalus, and ventriculoperitoneal (VP) shunt placement. Specifically, these patients had significantly higher rates of EVD placement (23% vs 1%, p < 0.001), hydrocephalus (6% vs 0%, p = 0.03), IVH (14% vs 0%, p < 0.001), infection (15% vs 5%, p = 0.04), and subgaleal collection (20% vs 4%, p < 0.001). It was also observed that VP shunt placement was only seen in cases of ventricular entry (11% vs 0%, p = 0.001) with 3 of 4 of these patients having a large ventricular entry (defined here as entry greater than a pinhole [< 3 mm] entry). Furthermore, in a subset of glioblastoma patients with and without ventricular entry, Kaplan-Meier estimates for survival demonstrated a median survival time of 329 days for ventricular entry compared with 522 days for patients with no ventricular entry (HR 1.13, 95% CI 0.65-1.96; p = 0.67). CONCLUSIONS There are more complications associated with ventricular entry during brain tumor resection than in nonviolated ventricular systems. Better strategies for management of periventricular tumor resection should be actively sought to improve resection and survival for these patients.

Further evidence for a pain pathway involving the cingulate gyrus: a case of chronic cluster headache cured by glioblastoma

The authors report a case of a 49-year-old man with long-standing, chronic cluster headache (CH) refractory to medical therapy and occipital nerve stimulation that resolved a few weeks prior to the diagnosis of glioblastoma involving primarily the right cingulate gyrus. An attempt to explore the underlying role of the cingulate cortex in pain modulation by appraising the current literature is presented. This report suggests that the cingulate gyri could be a potential target for neuromodulation in patients with medically refractory chronic CH.

Through the patient's eyes: an emphasis on patient-centered values in operative decision making in the management of malignant glioma

The Joint Section on Tumors of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons is now in its 30th year. In many ways its growth and development has paralleled neurosurgery and medicine as a whole. This is most evident in our endeavor towards more patient-centered care and focus on quantity and quality of life. As the push towards evidence-based care continues, it is important to ensure that individualized care remains a guiding principle. Conscientious surgeons continue to refine techniques and develop technologies that push the boundaries of surgical efficacy while better defining the risks of surgery and the impacts of surgical complications. This article provides a review of the factors involved in minimizing risk and obtaining maximal outcomes for patients through insightful patient selection and evidence-based surgical decision-making. Herein, we present the philosophy and practice of the Hermelin Brain Tumor Center at the Henry Ford Health System as one type of approach to caring for the patient with a malignant glioma.

Current approaches to the treatment of metastatic brain tumours

Metastatic tumours involving the brain overshadow primary brain neoplasms in frequency and are an important complication in the overall management of many cancers. Importantly, advances are being made in understanding the molecular biology underlying the initial development and eventual proliferation of brain metastases. Surgery and radiation remain the cornerstones of the therapy for symptomatic lesions; however, image-based guidance is improving surgical technique to maximize the preservation of normal tissue, while more sophisticated approaches to radiation therapy are being used to minimize the long-standing concerns over the toxicity of whole-brain radiation protocols used in the past. Furthermore, the burgeoning knowledge of tumour biology has facilitated the entry of systemically administered therapies into the clinic. Responses to these targeted interventions have ranged from substantial toxicity with no control of disease to periods of useful tumour control with no decrement in performance status of the treated individual. This experience enables recognition of the limits of targeted therapy, but has also informed methods to optimize this approach. This Review focuses on the clinically relevant molecular biology of brain metastases, and summarizes the current applications of these data to imaging, surgery, radiation therapy, cytotoxic chemotherapy and targeted therapy.

Neuroblast division during migration toward the ischemic striatum: a study of dynamic migratory and proliferative characteristics of neuroblasts from the subventricular zone

Ischemic stroke induces neurogenesis in the subventricular zone (SVZ), and newly generated neurons in the SVZ migrate toward the ischemic boundary. However, the characteristics of migrating SVZ cells have not been investigated after stroke. Using time-lapse imaging in both SVZ cells and organotypic brain slice cultures, we measured the dynamics of SVZ cell division and migration of adult rats subjected to stroke. In normal brain slices, SVZ cells primarily migrated dorsally and ventrally along the lateral ventricular surface. However, in stroke brain slices, SVZ cells migrated laterally toward the striatal ischemic boundary. Cultured stroke-derived SVZ cells exhibited a significant (p < 0.01) increase in the migration distance (212 +/- 21 microm) compared with the nonstroke-derived SVZ cells (97 +/- 12 microm). Migrating stroke-derived SVZ cells spent significantly (p = 0.01) less time in cytokinesis (0.63 +/- 0.04 h) compared with the time (1.09 +/- 0.09 h) for nonstroke-derived SVZ cells. Newborn cells with a single leading process exhibited fast migration (7.2 +/- 0.8 microm/h), and cells with multiple processes showed stationary migration (3.6 +/- 0.8 microm/h). Stroke SVZ daughter cells further divided during their migration. The morphology of doublecortin (DCX)-positive cells in fixed brain sections resembled those observed in cultured newborn cells, and the DCX-positive cells proliferated in the ischemic striatum. Collectively, the present study suggests that stroke promotes cytokinesis of migrating neuroblasts, and these cells migrate toward the ischemic striatum with distinct migratory behaviors and retain the capacity for cell division during migration.

Stromal cell-derived factor 1alpha mediates neural progenitor cell motility after focal cerebral ischemia

In the adult rodent, stroke induces an increase in endogenous neural progenitor cell (NPC) proliferation in the subventricular zone (SVZ) and neuroblasts migrate towards the ischemic boundary. We investigated the role of stromal cell-derived factor 1alpha (SDF-1alpha) in mediating NPC migration after stroke. We found that cultured NPCs harvested from the normal adult SVZ, when they were overlaid onto stroke brain slices, exhibited significantly (P<0.01) increased migration (67.2+/-25.2 microm) compared with the migration on normal brain slices (29.5+/-29.5 microm). Immunohistochemistry showed that CXCR 4, a receptor of SDF-1alpha, is expressed in the NPCs and migrating neuroblasts in stroke brain. Blocking SDF-1alpha by a neutralizing antibody against CXCR 4 significantly attenuated stroke-enhanced NPC migration. ELISA analysis revealed that SDF-1alpha levels significantly increased (P<0.01) in the stroke hemisphere (43.6+/-6.5 pg/mg) when compared with the normal brain (25.2+/-1.9 pg/mg). Blind-well chamber assays showed that SDF-1alpha enhanced NPC migration in a dose-dependent manner with maximum migration at a dose of 500 ng/mL. In addition, SDF-1alpha induced directionally selective migration. These findings show that SDF-1alpha generated in the stroke hemisphere may guide NPC migration towards the ischemic boundary via binding to its receptor CXCR 4 in the NPC. Thus, our data indicate that SDF-1alpha/CXCR 4 is important for mediating specific migration of NPCs to the site of ischemic damaged neurons.

Biphasic effects of exogenous VEGF on VEGF expression of adult neural progenitors

Vascular endothelial growth factor (VEGF) regulates neurogenesis. The present study investigated the direct effect of VEGF on the enhancement of proliferation and differentiation of the adult mouse subventricular zone (SVZ) neural progenitors in vitro. A high dose (500 ng/ml) of VEGF significantly downregulated endogenous VEGF receptors 1 and 2, which was associated with significantly reduced neural progenitor cell proliferation and enhancement of neuronal differentiation. A low dose (50 ng/ml) of VEGF significantly upregulated endogenous VEGF receptors 1 and 2 but did not increase proliferation and differentiation. These data suggest that exogenous VEGF has a biphasic effect on the expression of endogenous VEGF receptors, and the high dose of VEGF enhances adult neural progenitor cell differentiation into neurons.

Low-dose photodynamic therapy increases endothelial cell proliferation and VEGF expression in nude mice brain

We tested whether low-dose photodynamic therapy (PDT) induces an angiogenic response in the normal brain of nude mice (n=20). Normal brains of nude mice were subjected to PDT at low doses (Photofrin: 2 mg/kg; optical: 2 J/cm(2) and 4 J/cm(2)). BrdU (50 mg/kg) was injected (intraperitoneally, i.p.) daily from PDT treatment to sacrifice (1 and 2 weeks after PDT). Laser scanning confocal microscopy, immunohistochemistry, and immunofluorescence staining were performed to assay angiogenic response. Morphological results show no significant tissue damage induced by PDT and two- and three-dimensional image analyses revealed no significant difference in vascular structure between the areas of exposure to PDT and contralateral areas in all mice. However, the number of BrdU immunoreactive cells were significantly increased in the areas of PDT treatment compared with contralateral hemisphere in both groups, and the number of BrdU-positive cells increased in a PDT-dose-dependent manner. Furthermore, immunohistochemical data indicate that PDT at these low doses significantly induces the expression of the vascular endothelial growth factor (VEGF) in PDT-treated regions in the 1-week group, but not in the 2-week group. These data indicate that low-dose PDT results in increased VEGF expression and endothelial cell proliferation in normal brains.

A Quantitative Model of Tumor-induced Angiogenesis in the Nude Mouse

OBJECTIVE

Novel animal models allowing for the quantification of tumor-induced angiogenesis and cell migration may offer significant insight into the characterization and multidisciplinary treatment of brain tumors. In this study, we seek to establish such a model in tumor-bearing brain, allowing for a clear demarcation of primary and satellite tumor tissue in conjunction with precise quantification of cerebral microvasculature.

METHODS

We used green fluorescent protein-transfected 9L-gliosarcoma cells stereotactically injected into the brain parenchyma of nude mice perfused with tetramethylrhodamine-dextran immediately before they were killed. New three-dimensional analytical software developed in our laboratory provided a quantitative analysis of laser-scanning confocal microscopy images of dextran-labeled cerebral microvessels.

RESULTS

Our data confirm significant angiogenesis in tumor and brain adjacent to tumor.

CONCLUSION

Because these highly infiltrative malignant brain tumors interdigitate with normal brain parenchyma through finger-like projections at the periphery of the solid tumor boundary, therapeutic options targeting tumor blood flow--combined with novel three-dimensional imaging to localize and track such interventions--may offer new hope for glioma management. To our knowledge, this system represents the first animal brain tumor model allowing for the precise colocalization and quantification of angiogenesis and tumor cell invasion, which may play an important role in the development of future therapy for brain tumors.

Angiogenesis induced by photodynamic therapy in normal rat brains

Angiogenesis promotes tumor growth and invasiveness in brain. Because brain injury often induces expression of angiogenic-promoting molecules, we hypothesize that oxidative insult induced by photodynamic therapy (PDT) could lead to an endogenous angiogenic response, possibly diminishing the efficacy of PDT treatment of tumors. Therefore, we sought to establish whether PDT induced an angiogenic response within the nontumored brain. PDT using Photofrin as a sensitizer at an optical dose of 140 J/cm2 was performed on normal rat brain (n = 30). Animals were sacrificed at 24 h, and 1, 2, 3 and 6 weeks after PDT treatment. Fluorescein isothiocyanatedextran perfusion was performed, and brains were fixed for immunohistological study. Immunostaining revealed that vascular endothelial growth factor (VEGF) expression increased within the PDT-treated hemisphere 1 week after treatment and remained elevated for 6 weeks. Three-dimensional morphologic analysis of vasculature within PDT-treated and contralateral brain demonstrated PDT-induced angiogenesis, as indicated by a significant increase in vessel connectivity (P < 0.001) concomitant with decreased (P < 0.05) mean segment length compared with vessels within the contralateral hemisphere. Volumetric measurement of angiogenic regions indicate that neovascular expansion continued for 4 weeks after PDT. These data demonstrate that PDT induces VEGF expression and neovascularization within normal brain. Because angiogenesis promotes growth and invasiveness of tumor, antagonizing this endogenous angiogenic response to PDT may present a practical means to enhance the efficacy of PDT.

In vivo magnetic resonance imaging tracks adult neural progenitor cell targeting of brain tumor

Using magnetic resonance imaging (MRI), we described a method for noninvasively tracking grafted neural progenitor cells and bone marrow stromal cells (MSCs) in brain tumor of the rat. Neural progenitor cells and MSCs were labeled with lipophilic dye-coated superparamagnetic particles. The labeled neural progenitor cells and MSCs were transplanted to rats via the cisterna magna and a tail vein, respectively, 1 week after 9L-gliosarcoma cell implantation. Three-dimensional (3D) gradient echo and contrast agent images revealed dynamic migration of adult neural progenitor cells and MSCs detected by loss of MRI signals towards tumor mass and infiltrated tumor cells. Prussian blue staining and fluorescent microscope analysis showed that grafted cells targeted tumor cells and areas with grafted cells corresponded to areas with loss of MRI signals. These results demonstrate that the MRI technique provides a sensitive method for in vivo assessment of grafted cells targeting tumor mass and infiltrated tumor cells and that adult neural progenitor cells and MSCs can target tumor aggregates in the brain.

Photodynamic therapy with photofrin in combination with Buthionine Sulfoximine (BSO) of human glioma in the nude rat

High concentrations of cellular glutathione (GSH) within tumour cells may reduce the ability of photodynamic therapy (PDT) to selectively destroy tumour, consequently, a means of improving the therapeutic ratio of PDT in brain tumour is necessary. Therefore, we hypothesize that PDT in combination with Buthionine Sulfoximine (BSO), an agent which lowers cellular glutathione, can significantly enhance destruction of U87 and U251n tumour cells. PDT was performed using Photofrin as a photosensitiser in combination with BSO administration on male Fisher rats with intracerebral U87 and on non-tumour rats (administered at different optical doses in combination with Photofrin). In vitro experimentation utilising colony forming, cell cytotoxicity, and matrigel artificial basement membrane invasion assays showed significant enhancement of tumour kill and significant reduction of migration in tumour cells treated with BSO in combination with Photofrin PDT in comparison with individual therapies for both U87 and U251n cell lines. In vivo combination PDT-BSO treatment of U87 tumour rats exhibited significantly more tumour necrosis than individual treatments. In conclusion, our data suggests BSO enhances Photofrin PDT treatment of human glioma.