Glioma Extent of Resection and Ultra-Low-Field iMRI: Interim Analysis of a Prospective Randomized Trial

Simulation of surgery for supratentorial gliomas in virtual reality using a 3D volume rendering technique: a poor man's neuronavigation

OBJECTIVE

Different techniques of performing image-guided neurosurgery exist, namely, neuronavigation systems, intraoperative ultrasound, and intraoperative MRI, each with its limitations. Except for ultrasound, other methods are expensive. Three-dimensional virtual reconstruction and surgical simulation using 3D volume rendering (VR) is an economical and excellent technique for preoperative surgical planning and image-guided neurosurgery. In this article, the authors discuss several nuances of the 3D VR technique that have not yet been described.

METHODS

The authors included 6 patients with supratentorial gliomas who underwent surgery between January 2019 and March 2021. Preoperative clinical data, including patient demographics, preoperative planning details (done using the VR technique), and intraoperative details, including relevant photos and videos, were collected. RadiAnt software was used for generating virtual 3D images using the VR technique on a computer running Microsoft Windows.

RESULTS

The 3D VR technique assists in glioma surgery with a preoperative simulation of the skin incision and craniotomy, virtual cortical surface marking and navigation for deep-seated gliomas, preoperative visualization of morbid cortical surface and venous anatomy in surfacing gliomas, identifying the intervenous surgical corridor in both surfacing and deep-seated gliomas, and pre- and postoperative virtual 3D images highlighting the exact spatial geometric residual tumor location and extent of resection for low-grade gliomas (LGGs).

CONCLUSIONS

Image-guided neurosurgery with the 3D VR technique using RadiAnt software is an economical, easy-to-learn, and user-friendly method of simulating glioma surgery, especially in resource-constrained countries where expensive neuronavigation systems are not readily available. Apart from cortical sulci/gyri anatomy, FLAIR sequences are ideal for the 3D visualization of nonenhancing diffuse LGGs using the VR technique. In addition to cortical vessels (especially veins), contrast MRI sequences are perfect for the 3D visualization of contrast-enhancing high-grade gliomas.

5-ALA in Suspected Low-Grade Gliomas: Current Role, Limitations, and New Approaches

Radiologically suspected low-grade gliomas (LGG) represent a special challenge for the neurosurgeon during surgery due to their histopathological heterogeneity and indefinite tumor margin. Therefore, new techniques are required to overcome these current surgical drawbacks. Intraoperative visualization of brain tumors with assistance of 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) fluorescence is one of the major advancements in the neurosurgical field in the last decades. Initially, this technique was exclusively applied for fluorescence-guided surgery of high-grade glioma (HGG). In the last years, the use of 5-ALA was also extended to other indications such as radiologically suspected LGG. Here, we discuss the current role of 5-ALA for intraoperative visualization of focal malignant transformation within suspected LGG. Furthermore, we discuss the current limitations of the 5-ALA technology in pure LGG which usually cannot be visualized by visible fluorescence. Finally, we introduce new approaches based on fluorescence technology for improved detection of pure LGG tissue such as spectroscopic PpIX quantification fluorescence lifetime imaging of PpIX and confocal microscopy to optimize surgery.

Intraoperative Magnetic Resonance Imaging for Low-Grade and High-Grade Gliomas: What Is the Evidence? A Meta-Analysis

BACKGROUND

The benefit of intraoperative magnetic resonance imaging (iMRI) in gliomas remains unclear. We performed a meta-analysis of outcomes with iMRI-guided surgery in high-grade gliomas (HGGs) and low-grade gliomas (LGGs).

METHODS

Databases were searched until November 29, 2018 for randomized controlled trials (RCTs) and observational studies (OBS) comparing iMRI use with conventional neurosurgery. Pooled risk ratios (RRs) or hazard ratios were evaluated with the random-effects model. Outcomes included extent of resection (EOR), gross total resection (GTR), progression-free survival (PFS), overall survival (OS), and length of surgery (LOS), stratified by study design and glioma grade.

RESULTS

Fifteen articles (3 RCTs and 12 OBS) were included. In RCTs, GTR was higher in iMRI compared with conventional neurosurgery (RR, 1.42; 95% confidence interval [CI], 1.17-1.73; I², 7%) overall, for LGGs (1.91; 95% CI, 1.19-3.06), but not HGGs (1.24; 95% CI, 0.89-1.73), with no difference in EOR, PFS, OS, and LOS. For OBS, GTR was higher (RR, 1.65; 95% CI, 1.43-1.90; I², 4%) overall, and for LGGs (1.63; 95% CI, 1.17-2.28; I², 0%) and HGGs (1.62; 95% CI, 1.36-1.92; I², 19%). EOR was greater with iMRI (6%; 95% CI, 4%-8%; I², 44%) overall, in LGGs (5%; 95% CI, 2%-8%; I², 37%) and HGGs (7%; 95% CI, 4%-10%; I², 13%). There was no difference in PFS, OS, and LOS with iMRI.

CONCLUSIONS

IMRI use improved GTR in gliomas, including LGGs. However, no PFS and OS benefit was shown in the meta-analysis.

Intraoperative imaging technology to maximise extent of resection for glioma: a network meta-analysis

BACKGROUND

Multiple studies have identified the prognostic relevance of extent of resection in the management of glioma. Different intraoperative technologies have emerged in recent years with unknown comparative efficacy in optimising extent of resection. One previous Cochrane Review provided low- to very low-certainty evidence in single trial analyses and synthesis of results was not possible. The role of intraoperative technology in maximising extent of resection remains uncertain. Due to the multiple complementary technologies available, this research question is amenable to a network meta-analysis methodological approach.

OBJECTIVES

To establish the comparative effectiveness and risk profile of specific intraoperative imaging technologies using a network meta-analysis and to identify cost analyses and economic evaluations as part of a brief economic commentary.

SEARCH METHODS

We searched CENTRAL (2020, Issue 5), MEDLINE via Ovid to May week 2 2020, and Embase via Ovid to 2020 week 20. We performed backward searching of all identified studies. We handsearched two journals, Neuro-oncology and the Journal of Neuro-oncology from 1990 to 2019 including all conference abstracts. Finally, we contacted recognised experts in neuro-oncology to identify any additional eligible studies and acquire information on ongoing randomised controlled trials (RCTs).

SELECTION CRITERIA

RCTs evaluating people of all ages with presumed new or recurrent glial tumours (of any location or histology) from clinical examination and imaging (computed tomography (CT) or magnetic resonance imaging (MRI), or both). Additional imaging modalities (e.g. positron emission tomography, magnetic resonance spectroscopy) were not mandatory. Interventions included fluorescence-guided surgery, intraoperative ultrasound, neuronavigation (with or without additional image processing, e.g. tractography), and intraoperative MRI.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results for relevance, undertook critical appraisal according to known guidelines, and extracted data using a prespecified pro forma.

MAIN RESULTS

We identified four RCTs, using different intraoperative imaging technologies: intraoperative magnetic resonance imaging (iMRI) (2 trials, with 58 and 14 participants); fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) (1 trial, 322 participants); and neuronavigation (1 trial, 45 participants). We identified one ongoing trial assessing iMRI with a planned sample size of 304 participants for which results are expected to be published around winter 2020. We identified no published trials for intraoperative ultrasound. Network meta-analyses or traditional meta-analyses were not appropriate due to absence of homogeneous trials across imaging technologies. Of the included trials, there was notable heterogeneity in tumour location and imaging technologies utilised in control arms. There were significant concerns regarding risk of bias in all the included studies. One trial of iMRI found increased extent of resection (risk ratio (RR) for incomplete resection was 0.13, 95% confidence interval (CI) 0.02 to 0.96; 49 participants; very low-certainty evidence) and one trial of 5-ALA (RR for incomplete resection was 0.55, 95% CI 0.42 to 0.71; 270 participants; low-certainty evidence). The other trial assessing iMRI was stopped early after an unplanned interim analysis including 14 participants; therefore, the trial provided very low-quality evidence. The trial of neuronavigation provided insufficient data to evaluate the effects on extent of resection. Reporting of adverse events was incomplete and suggestive of significant reporting bias (very low-certainty evidence). Overall, the proportion of reported events was low in most trials and, therefore, issues with power to detect differences in outcomes that may or may not have been present. Survival outcomes were not adequately reported, although one trial reported no evidence of improvement in overall survival with 5-ALA (hazard ratio (HR) 0.82, 95% CI 0.62 to 1.07; 270 participants; low-certainty evidence). Data for quality of life were only available for one study and there was significant attrition bias (very low-certainty evidence).

AUTHORS' CONCLUSIONS

Intraoperative imaging technologies, specifically 5-ALA and iMRI, may be of benefit in maximising extent of resection in participants with high-grade glioma. However, this is based on low- to very low-certainty evidence. Therefore, the short- and long-term neurological effects are uncertain. Effects of image-guided surgery on overall survival, progression-free survival, and quality of life are unclear. Network and traditional meta-analyses were not possible due to the identified high risk of bias, heterogeneity, and small trials included in this review. A brief economic commentary found limited economic evidence for the equivocal use of iMRI compared with conventional surgery. In terms of costs, one non-systematic review of economic studies suggested that, compared with standard surgery, use of image-guided surgery has an uncertain effect on costs and that 5-ALA was more costly. Further research, including completion of ongoing trials of ultrasound-guided surgery, is needed.

Cost-Effectiveness of Low-Field Intraoperative Magnetic Resonance in Glioma Surgery

Object

Low-field intraoperative magnetic resonance (LF-iMR) has demonstrated a slight increase in the extent of resection of intra-axial tumors while preserving patient`s neurological outcomes. However, whether this improvement is cost-effective or not is still matter of controversy. In this clinical investigation we sought to evaluate the cost-effectiveness of the implementation of a LF-iMR in glioma surgery.

Methods

Patients undergoing LF-iMR guided glioma surgery with gross total resection (GTR) intention were prospectively collected and compared to an historical cohort operated without this technology. Socio-demographic and clinical variables (pre and postoperative KPS; histopathological classification; Extent of resection; postoperative complications; need of re-intervention within the first year and 1-year postoperative survival) were collected and analyzed. Effectiveness variables were assessed in both groups: Postoperative Karnofsky performance status scale (pKPS); overall survival (OS); Progression-free survival (PFS); and a variable accounting for the number of patients with a greater than subtotal resection and same or higher postoperative KPS (R-KPS). All preoperative, procedural and postoperative costs linked to the treatment were considered for the cost-effectiveness analysis (diagnostic procedures, prosthesis, operating time, hospitalization, consumables, LF-iMR device, etc). Deterministic and probabilistic simulations were conducted to evaluate the consistency of our analysis.

Results

50 patients were operated with LF-iMR assistance, while 146 belonged to the control group. GTR rate, pKPS, R-KPS, PFS, and 1-year OS were respectively 13,8% (not significative), 7 points (p < 0.05), 17% (p < 0.05), 38 days (p < 0.05), and 3.7% (not significative) higher in the intervention group. Cost-effectiveness analysis showed a mean incremental cost per patient of 789 € in the intervention group. Incremental cost-effectiveness ratios were 111 € per additional point of pKPS, 21 € per additional day free of progression, and 46 € per additional percentage point of R-KPS.

Conclusion

Glioma patients operated under LF-iMR guidance experience a better functional outcome, higher resection rates, less complications, better PFS rates but similar life expectancy compared to conventional techniques. In terms of efficiency, LF-iMR is very close to be a dominant technology in terms of R-KPS, PFS and pKPS.

Cost-effectiveness of Intraoperative MRI for Treatment of High-Grade Gliomas

Background Intraoperative MRI has been shown to improve gross-total resection of high-grade glioma. However, to the knowledge of the authors, the cost-effectiveness of intraoperative MRI has not been established. Purpose To construct a clinical decision analysis model for assessing intraoperative MRI in the treatment of high-grade glioma. Materials and Methods An integrated five-state microsimulation model was constructed to follow patients with high-grade glioma. One-hundred-thousand patients treated with intraoperative MRI were compared with 100 000 patients who were treated without intraoperative MRI from initial resection and debulking until death (median age at initial resection, 55 years). After the operation and treatment of complications, patients existed in one of three health states: progression-free survival (PFS), progressive disease, or dead. Patients with recurrence were offered up to two repeated resections. PFS, valuation of health states (utility values), probabilities, and costs were obtained from randomized controlled trials whenever possible. Otherwise, national databases, registries, and nonrandomized trials were used. Uncertainty in model inputs was assessed by using deterministic and probabilistic sensitivity analyses. A health care perspective was used for this analysis. A willingness-to-pay threshold of $100 000 per quality-adjusted life year (QALY) gained was used to determine cost efficacy. Results Intraoperative MRI yielded an incremental benefit of 0.18 QALYs (1.34 QALYs with intraoperative MRI vs 1.16 QALYs without) at an incremental cost of $13 447 ($176 460 with intraoperative MRI vs $163 013 without) in microsimulation modeling, resulting in an incremental cost-effectiveness ratio of $76 442 per QALY. Because of parameter distributions, probabilistic sensitivity analysis demonstrated that intraoperative MRI had a 99.5% chance of cost-effectiveness at a willingness-to-pay threshold of $100 000 per QALY. Conclusion Intraoperative MRI is likely to be a cost-effective modality in the treatment of high-grade glioma. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Bettmann in this issue.

How to Build a Neurosurgical Oncology Practice Specializing in Gliomas

For the neurosurgical oncologist, a specialty practice in gliomas represents an intersection of tailored surgical approaches, emerging intraoperative technologies, expanding surgical trial portfolios, and new paradigms in glioma biology. Assembling these disparate pieces into a cohesive career trajectory is a difficult task but ultimately enables the subspecialist to navigate all domains relevant to improving glioma patient outcomes. Within the larger clinical and basic science community, thoughtful integration and intensive collaborations are essential mechanisms when building a multidisciplinary glioma program.

Intraoperative imaging technology to maximise extent of resection for glioma

BACKGROUND

Extent of resection is considered to be a prognostic factor in neuro-oncology. Intraoperative imaging technologies are designed to help achieve this goal. It is not clear whether any of these sometimes very expensive tools (or their combination) should be recommended as standard care for people with brain tumours. We set out to determine if intraoperative imaging technology offers any advantage in terms of extent of resection over standard surgery and if any one technology was more effective than another.

OBJECTIVES

To establish the overall effectiveness and safety of intraoperative imaging technology in resection of glioma. To supplement this review of effects, we also wished to identify cost analyses and economic evaluations as part of a Brief Economic Commentary (BEC).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 7, 2017), MEDLINE (1946 to June, week 4, 2017), and Embase (1980 to 2017, week 27). We searched the reference lists of all identified studies. We handsearched two journals, the Journal of Neuro-Oncology and Neuro-oncology, from 1991 to 2017, including all conference abstracts. We contacted neuro-oncologists, trial authors, and manufacturers regarding ongoing and unpublished trials.

SELECTION CRITERIA

Randomised controlled trials evaluating people of all ages with presumed new or recurrent glial tumours (of any location or histology) from clinical examination and imaging (computed tomography (CT) or magnetic resonance imaging (MRI), or both). Additional imaging modalities (e.g. positron emission tomography, magnetic resonance spectroscopy) were not mandatory. Interventions included intraoperative MRI (iMRI), fluorescence-guided surgery, ultrasound, and neuronavigation (with or without additional image processing, e.g. tractography).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results for relevance, undertook critical appraisal according to known guidelines, and extracted data using a prespecified pro forma.

MAIN RESULTS

We identified four randomised controlled trials, using different intraoperative imaging technologies: iMRI (2 trials including 58 and 14 participants, respectively); fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) (1 trial, 322 participants); and neuronavigation (1 trial, 45 participants). We identified one ongoing trial assessing iMRI with a planned sample size of 304 participants for which results are expected to be published around autumn 2018. We identified no trials for ultrasound.Meta-analysis was not appropriate due to differences in the tumours included (eloquent versus non-eloquent locations) and variations in the image guidance tools used in the control arms (usually selective utilisation of neuronavigation). There were significant concerns regarding risk of bias in all the included studies. All studies included people with high-grade glioma only.Extent of resection was increased in one trial of iMRI (risk ratio (RR) of incomplete resection 0.13, 95% confidence interval (CI) 0.02 to 0.96; 1 study, 49 participants; very low-quality evidence) and in the trial of 5-ALA (RR of incomplete resection 0.55, 95% CI 0.42 to 0.71; 1 study, 270 participants; low-quality evidence). The other trial assessing iMRI was stopped early after an unplanned interim analysis including 14 participants, therefore the trial provides very low-quality evidence. The trial of neuronavigation provided insufficient data to evaluate the effects on extent of resection.Reporting of adverse events was incomplete and suggestive of significant reporting bias (very low-quality evidence). Overall, reported events were low in most trials. There was no clear evidence of improvement in overall survival with 5-ALA (hazard ratio 0.83, 95% CI 0.62 to 1.07; 1 study, 270 participants; low-quality evidence). Progression-free survival data were not available in an appropriate format for analysis. Data for quality of life were only available for one study and suffered from significant attrition bias (very low-quality evidence).

AUTHORS' CONCLUSIONS

Intra-operative imaging technologies, specifically iMRI and 5-ALA, may be of benefit in maximising extent of resection in participants with high grade glioma. However, this is based on low to very low quality evidence, and is therefore very uncertain. The short- and long-term neurological effects are uncertain. Effects of image-guided surgery on overall survival, progression-free survival, and quality of life are unclear. A brief economic commentary found limited economic evidence for the equivocal use of iMRI compared with conventional surgery. In terms of costs, a non-systematic review of economic studies suggested that compared with standard surgery use of image-guided surgery has an uncertain effect on costs and that 5-aminolevulinic acid was more costly. Further research, including studies of ultrasound-guided surgery, is needed.

Defining Glioblastoma Resectability Through the Wisdom of the Crowd: A Proof-of-Principle Study

BACKGROUND

Extent of resection (EOR) correlates with glioblastoma outcomes. Resectability and EOR depend on anatomical, clinical, and surgeon factors. Resectability likely influences outcome in and of itself, but an accurate measurement of resectability remains elusive. An understanding of resectability and the factors that influence it may provide a means to control a confounder in clinical trials and provide reference for decision making.

OBJECTIVE

To provide proof of concept of the use of the collective wisdom of experienced brain tumor surgeons in assessing glioblastoma resectability.

METHODS

We surveyed 13 academic tumor neurosurgeons nationwide to assess the resectability of newly diagnosed glioblastoma. Participants reviewed 20 cases, including digital imaging and communications in medicine-formatted pre- and postoperative magnetic resonance images and clinical vignettes. The selected cases involved a variety of anatomical locations and a range of EOR. Participants were asked about surgical goal, eg, gross total resection, subtotal resection (STR), or biopsy, and rationale for their decision. We calculated a "resectability index" for each lesion by pooling responses from all 13 surgeons.

RESULTS

Neurosurgeons' individual surgical goals varied significantly ( P = .015), but the resectability index calculated from the surgeons' pooled responses was strongly correlated with the percentage of contrast-enhancing residual tumor ( R = 0.817, P < .001). The collective STR goal predicted intraoperative decision of intentional STR documented on operative notes ( P < .01) and nonresectable residual ( P < .01), but not resectable residual.

CONCLUSION

In this pilot study, we demonstrate the feasibility of measuring the resectability of glioblastoma through crowdsourcing. This tool could be used to quantify resectability, a potential confounder in neuro-oncology clinical trials.

Intraoperative high-field magnetic resonance imaging, multimodal neuronavigation, and intraoperative electrophysiological monitoring-guided surgery for treating supratentorial cavernomas

Objective

To determine the beneficial effects of intraoperative high-field magnetic resonance imaging (MRI), multimodal neuronavigation, and intraoperative electrophysiological monitoring-guided surgery for treating supratentorial cavernomas.

Methods

Twelve patients with 13 supratentorial cavernomas were prospectively enrolled and operated while using a 1.5 T intraoperative MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring. All cavernomas were deeply located in subcortical areas or involved critical areas. Intraoperative high-field MRIs were obtained for the intraoperative “visualization” of surrounding eloquent structures, “brain shift” corrections, and navigational plan updates.

Results

All cavernomas were successfully resected with guidance from intraoperative MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring. In 5 cases with supratentorial cavernomas, intraoperative “brain shift” severely deterred locating of the lesions; however, intraoperative MRI facilitated precise locating of these lesions. During long-term (>3 months) follow-up, some or all presenting signs and symptoms improved or resolved in 4 cases, but were unchanged in 7 patients.

Conclusions

Intraoperative high-field MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring are helpful in surgeries for the treatment of small deeply seated subcortical cavernomas.

Impact of intraoperative MRI-guided resection on resection and survival in patient with gliomas: a meta-analysis

OBJECTIVE

This study addressed the benefit of intraoperative magnetic resonance imaging (iMRI) compared with conventional neuronavigation-guided resection in patients with gliomas.

RESEARCH DESIGN AND METHODS

The Medline, PubMed, Cochrane, and Google Scholar databases were searched up to 26 September 2015. Randomized controlled trials (RCTs), two-arm prospective studies, and retrospective studies in patients with glioblastoma/glioma who had received surgical treatment were included.

MAIN OUTCOME MEASURES

The primary outcome measures were the extent of tumor resection and tumor size reduction for using iMRI-guided or conventional neuronavigation-guided neurosurgery. Secondary outcomes included impact of surgery on 6 month progression-free survival (PFS), 12 month overall survival (OS) rates and surgical duration.

RESULTS

We found that iMRI was associated with greater rate of gross total resection (rGTR) compared with conventional neuronavigation procedures (3.16, 95% confidence interval [CI] 2.07-4.83, P < .001). We found no difference between the two neuronavigation approaches in extent of resection (EOR), tumor size reduction, or time required for surgery (P values ≥.065). Intraoperative MRI was associated with a higher rate of progression-free survival (PFS) compared with conventional neuronavigation (odds ratio, 1.84; 95% CI 1.15-2.95; P = .012), but the rate of overall survival (OS) between groups was similar (P = .799). Limitations of the study included the fact that data from non-RCTs was used, the small study population, and heterogeneity of outcomes across studies.

CONCLUSIONS

Our findings indicate that iMRI more frequently resulted in more complete resections leading to improved PFS in patients with malignant gliomas.

Optimization of tumor resection with intra-operative magnetic resonance imaging

Intra-operative MRI (ioMRI) may be used to optimize tumor resection. Utilization of this technology allows for the removal of residual tumor mass following initial tumor removal, maximizing the extent of resection. This, in turn, has been shown to lead to improved outcomes. Individual studies have examined the impact of ioMRI on the rate of extended resection, but a comprehensive review of this topic is needed. A literature review of the MEDLINE, EMBASE, CENTRAL, and Google Scholar databases revealed 12 eligible studies. This included 804 primary operations and 238 extended resections based on ioMRI findings. Use of ioMRI led to extended tumor resection in 13.3-54.8% of patients (mean 37.3%). Stratification by tumor type showed additional resection occurred, on average, in 39.1% of glioma resections (range 13.3-70.0%), 23.5% of pituitary tumor resections (range 13.3-33.7%), and 35.0% of nonspecific tumor resections (range 17.5-40%). Tumor type (glioma vs. pituitary) did not significantly influence the rate of further excision following ioMRI (p=0.309). There was no difference in secondary resection rate between studies limited to pediatric patients and those including adults (p=0.646). Thus, the use of intra-operative MRI frequently results in further resection of tumors. It is primarily used for the resection of gliomas and pituitary tumors. Tumor type does not appear to be a significant contributing factor to the rate of secondary tumor removal. Limited evidence suggests that extended resection may translate into improved clinical outcomes and mortality rates. However, results have not been unanimous, while clinical effect sizes have often been modest.

Glioblastoma stem cells: new insights in therapeutic strategies

ABSTRACT 

Despite notable achievements in glioblastoma diagnosis and treatment, the prognosis of glioblastoma patients remains poor and reflects the failure of current therapeutic modalities. In this context, innovative therapeutic strategies have recently been developed to specifically target glioblastoma stem cells, a subpopulation of tumor cells involved in experimental tumorigenesis and known to be critical for tumor recurrence and therapeutic resistance. The current review summarizes the different trails which make glioblastoma stem cells resistant to treatments, mainly focusing on radio-, chemo- and immunotherapy. This broad overview might actually help to set up new bases for glioblastoma therapy in order to better fight tumor relapses and to improve the patients’ prognosis.

Image guided surgery for the resection of brain tumours

BACKGROUND

Extent of resection is believed to be a key prognostic factor in neuro-oncology. Image guided surgery uses a variety of tools or technologies to help achieve this goal. It is not clear whether any of these, sometimes very expensive, tools (or their combination) should be recommended as part of standard care for patient with brain tumours. We set out to determine if image guided surgery offers any advantage in terms of extent of resection over surgery without any image guidance and if any one tool or technology was more effective.

OBJECTIVES

To compare image guided surgery with surgery either not using any image guidance or to compare surgery using two different forms of image guidance. The primary outcome criteria was extent of resection and adverse events. Other outcome criteria were overall survival; progression free survival; and quality of life (QoL).

SEARCH METHODS

The following databases were searched, the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 1, 2013), MEDLINE (1948 to March, week 10, 2013) and EMBASE (1970 to 2013, week 10). Reference lists of all identified studies were searched. Two journals, the Journal of Neuro-Oncology and Neuro-oncology, were handsearched from 1991 to 2013, including all conference abstracts. Neuro-oncologists, trial authors and manufacturers were contacted regarding ongoing and unpublished trials.

SELECTION CRITERIA

Study participants included patients of all ages with a presumed new or recurrent brain tumour (any location or histology) from clinical examination and imaging (computed tomography (CT), magnetic resonance imaging (MRI) or both). Image guidance interventions included intra-operative MRI (iMRI); fluorescence guided surgery; neuronavigation including diffusion tensor imaging (DTI); and ultrasonography. Included studies had to be randomised controlled trials (RCTs) with comparisons made either with patients having surgery without the image guidance tool in question or with another type of image guidance tool. Subgroups were to include high grade glioma; low grade glioma; brain metastasis; skull base meningiomas; and sellar or parasellar tumours.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results for relevance, undertook critical appraisal according to known guidelines, and extracted data using a pre-specified pro forma.

MAIN RESULTS

Four RCTs were identified, each using a different image guided technique: 1. iMRI (58 patients), 2. 5-aminolevulinic acid (5-ALA) fluorescence guided surgery (322 patients), 3. neuronavigation (45 patients) and 4. DTI-neuronavigation (238 patients). Meta-analysis was not appropriate due to differences in the tumours included (eloquent versus non-eloquent locations) and variations in the image guidance tools used in the control arms (usually selective utilisation of neuronavigation). There were significant concerns regarding risk of bias in all the included studies, especially for the study using DTI-neuronavigation. All studies included patients with high grade glioma, with one study also including patients with low grade glioma. The extent of resection was increased with iMRI (risk ratio (RR) (incomplete resection) 0.13, 95% CI 0.02 to 0.96, low quality evidence), 5-ALA (RR 0.55, 95% CI 0.42 to 0.71) and DTI-neuronavigation (RR 0.35, 95% CI 0.20 to 0.63, very low quality evidence). Insufficient data were available to evaluate the effects of neuronavigation on extent of resection. Reporting of adverse events was incomplete, with a suggestion of significant reporting bias. Overall, reported events were low in most studies, but there was concern that surgical resection using 5-ALA may lead to more frequent early neurological deficits. There was no clear evidence of improvement in overall survival (OS) with 5-ALA (hazard ratio (HR) 0.82, 95% CI 0.62 to 1.07) or DTI-neuronavigation (HR 0.57, 95% CI 0.32 to 1.00) in patients with high grade glioma. Progression-free survival (PFS) data were not available in the appropriate format for analysis.Data for quality of life (QoL) were only available for one study and suffered from significant attrition bias.

AUTHORS' CONCLUSIONS

There is low to very low quality evidence (according to GRADE criteria) that image guided surgery using iMRI, 5-ALA or DTI-neuronavigation increases the proportion of patients with high grade glioma that have a complete tumour resection on post-operative MRI. There is a theoretical concern that maximising the extent of resection may lead to more frequent adverse events but this was poorly reported in the included studies. Effects of image guided surgery on survival and QoL are unclear. Further research, including studies of ultrasound guided surgery, is needed.

Emerging operative strategies in neurosurgical oncology

PURPOSE OF REVIEW

In recent years, the safety and efficacy of neurosurgical intervention has rapidly improved for brain tumor patients. Technological advances, combined with refined intraoperative techniques, now enable well tolerated surgical access to any region of the human brain. For patients with gliomas, these improvements have redefined the clinical possibilities, and here we review several emerging operative strategies that are essential for next-generation neurosurgical oncologists and major brain tumor centers.

RECENT FINDINGS

The value of glioma extent of resection remains controversial, but review of the modern literature reveals important opportunities for early neurosurgical intervention. Although microsurgical resection must be balanced by the risk of neurological compromise, improvements in intraoperative stimulation techniques now enable resection of highly eloquent tumors with minimal morbidity. Additionally, the emergence of fluorescence-guided surgery as a new operative paradigm provides a unique opportunity to resect tumors to the margins of microscopic infiltration.

SUMMARY

Neurosurgical intervention remains the first step in effective glioma management. With intraoperative mapping techniques, aggressive microsurgical resection can be safely pursued even when tumors occupy essential functional pathways. With the development of tumor-specific fluorophores, such as 5-aminolevulinic acid, real-time microscopic visualization of tumor infiltration can be surgically targeted prior to adjuvant therapy.

Fluorescence-guided resection of primary and recurrent malignant gliomas with 5-aminolevulinic acid. Preliminary results

BACKGROUND AND PURPOSE

Extent of resection plays a key role in the treatment of malignant gliomas (MGs). Patients with complete glioma removal, followed by chemoradiation, obtain the longest overall and progression-free survival. Fluorescence-guided resection of MGs enables intraoperative visualization of glioma tissue and increases control of the resection. The authors present preliminary results of 5-aminolevulinic acid (5-ALA) application during the resection of primary and recurrent MGs.

MATERIAL AND METHODS

Six patients with either a suspected malignant glioma based on magnetic resonance imaging (MRI) or with recurrent glioblastoma multiforme were enrolled in the study. The extent of resection was calculated according to the postoperative MRI performed within 72 hours. Preoperative and early postoperative neurological status and Karnofsky Performance Scale (KPS) were compared.

RESULTS

Fluorescence of tumour tissue was observed in 5/6 patients (five with the histopathological diagnosis of glioblastoma multiforme and one with neurotoxoplasmosis and AIDS). Complete tumour resection was achieved in 5 patients. Postoperative KPS and neurological status deteriorated in 2 cases. Radiotherapy and chemotherapy did not interfere with the sensitivity of the fluorescence guided tumour visualization.

CONCLUSIONS

Fluorescence-guided resection of primary and recurrent MGs with 5-ALA improves control of the tumour resection. It enables the cytoreduction to be maximized but experience in neuro-oncological surgery is required to avoid serious, postoperative neurological deficits.

Intraoperative image guidance in neurosurgery: development, current indications, and future trends

Introduction. As minimally invasive surgery becomes the standard of care in neurosurgery, it is imperative that surgeons become skilled in the use of image-guided techniques. The development of image-guided neurosurgery represents a substantial improvement in the microsurgical treatment of tumors, vascular malformations, and other intracranial lesions. Objective. There have been numerous advances in neurosurgery which have aided the neurosurgeon to achieve accurate removal of pathological tissue with minimal disruption of surrounding healthy neuronal matter including the development of microsurgical, endoscopic, and endovascular techniques. Neuronavigation systems and intraoperative imaging should improve success in cranial neurosurgery. Additional functional imaging modalities such as PET, SPECT, DTI (for fiber tracking), and fMRI can now be used in order to reduce neurological deficits resulting from surgery; however the positive long-term effect remains questionable for many indications. Method. PubMed database search using the search term "image guided neurosurgery." More than 1400 articles were published during the last 25 years. The abstracts were scanned for prospective comparative trials. Results and Conclusion. 14 comparative trials are published. To date significant data amount show advantages in intraoperative accuracy influencing the perioperative morbidity and long-term outcome only for cerebral glioma surgery.

Prospective study on the efficacy of low-field intraoperative magnetic resonance imaging in neurosurgical operations

BACKGROUND AND PURPOSE

The application of intraoperative magnetic resonance imaging (iMRI) is related to a series of challenges of both a technical and an organizational nature. We present our experience in the application of low-field iMRI in everyday neurosurgical practice.

MATERIAL AND METHODS

A group of 58 patients operated on using low-field iMRI was subject to prospective controlled observation. The significance of differences in the range of preparation time, duration and direct operation results between the iMRI group and controls was analysed. The influence of epidemiological and demographic factors and technical aspects related to iMRI application on direct outcome of the surgery was assessed.

RESULTS

Twenty-eight tumour resections using craniotomy, 17 transsphenoidal resections of pituitary adenomas and 13 stereotactic procedures were conducted in the group of 24 men and 34 women operated on using iMRI. The control group was not significantly different in terms of epidemiological and demographic factors. The preparation and operation times were significantly longer in the iMRI group (p < 0.001 and p = 0.002, respectively). Longer duration of the surgery was not related to an increased frequency of complications. A higher percentage of postoperative improvement in neurological status (31% vs. 14%, p = 0.045), lower complication percentage (10% vs. 28%, p = 0.03) and a similar time of hospitalization (13 ± 7 vs. 12 ± 4 days, p = 0.33) were noted in the iMRI group.

CONCLUSIONS

The application of low-field iMRI prolongs the duration of neurosurgical procedures but does not negatively influence their safety. It is associated with above-average functional results and a lower percentage of total complications.

Intraoperative MRI guidance and extent of resection in glioma surgery: a randomised, controlled trial

BACKGROUND

Intraoperative MRI is increasingly used in neurosurgery, although there is little evidence for its use. We aimed to assess efficacy of intraoperative MRI guidance on extent of resection in patients with glioma.

METHODS

In our prospective, randomised, parallel-group trial, we enrolled adults (≥18 years) with contrast enhancing gliomas amenable to radiologically complete resection who presented to Goethe University (Frankfurt, Germany). We randomly assigned patients (1:1) with computer-generated blocks of four and a sealed-envelope design to undergo intraoperative MRI-guided surgery or conventional microsurgery (control group). Surgeons and patients were unmasked to treatment group allocation, but an independent neuroradiologist was masked during analysis of all preoperative and postoperative imaging data. The primary endpoint was rate of complete resections as established by early postoperative high-field MRI (1·5 T or 3·0 T). Analysis was done per protocol. This study is registered with ClinicalTrials.gov, number NCT01394692.

FINDINGS

We enrolled 58 patients between Oct 1, 2007, and July 1, 2010. 24 (83%) of 29 patients randomly allocated to the intraoperative MRI group and 25 (86%) of 29 controls were eligible for analysis (four patients in each group had metastasis and one patient in the intraoperative MRI group withdrew consent after randomisation). More patients in the intraoperative MRI group had complete tumour resection (23 [96%] of 24 patients) than did in the control group (17 [68%] of 25, p=0·023). Postoperative rates of new neurological deficits did not differ between patients in the intraoperative MRI group (three [13%] of 24) and controls (two [8%] of 25, p=1·0). No patient for whom use of intraoperative MRI led to continued resection of residual tumour had neurological deterioration. One patient in the control group died before 6 months.

INTERPRETATION

Our study provides evidence for the use of intraoperative MRI guidance in glioma surgery: such imaging helps surgeons provide the optimum extent of resection.

FUNDING

None.

Intraoperative confocal microscopy in the visualization of 5-aminolevulinic acid fluorescence in low-grade gliomas

OBJECT

Greater extent of resection (EOR) for patients with low-grade glioma (LGG) corresponds with improved clinical outcome, yet remains a central challenge to the neurosurgical oncologist. Although 5-aminolevulinic acid (5-ALA)-induced tumor fluorescence is a strategy that can improve EOR in gliomas, only glioblastomas routinely fluoresce following 5-ALA administration. Intraoperative confocal microscopy adapts conventional confocal technology to a handheld probe that provides real-time fluorescent imaging at up to 1000× magnification. The authors report a combined approach in which intraoperative confocal microscopy is used to visualize 5-ALA tumor fluorescence in LGGs during the course of microsurgical resection.

METHODS

Following 5-ALA administration, patients with newly diagnosed LGG underwent microsurgical resection. Intraoperative confocal microscopy was conducted at the following points: 1) initial encounter with the tumor; 2) the midpoint of tumor resection; and 3) the presumed brain-tumor interface. Histopathological analysis of these sites correlated tumor infiltration with intraoperative cellular tumor fluorescence.

RESULTS

Ten consecutive patients with WHO Grades I and II gliomas underwent microsurgical resection with 5-ALA and intraoperative confocal microscopy. Macroscopic tumor fluorescence was not evident in any patient. However, in each case, intraoperative confocal microscopy identified tumor fluorescence at a cellular level, a finding that corresponded to tumor infiltration on matched histological analyses.

CONCLUSIONS

Intraoperative confocal microscopy can visualize cellular 5-ALA-induced tumor fluorescence within LGGs and at the brain-tumor interface. To assess the clinical value of 5-ALA for high-grade gliomas in conjunction with neuronavigation, and for LGGs in combination with intraoperative confocal microscopy and neuronavigation, a Phase IIIa randomized placebo-controlled trial (BALANCE) is underway at the authors' institution.