Comparison of intraoperative fluorescence and MRI image guided neuronavigation in malignant brain tumours, a prospective controlled study

Focus session on sodium fluorescein in pediatric oncological neurosurgery

Many tools and techniques have been developed to obtain maximal safe tumoral resection in neurosurgery. Fluorescent dyes, including sodium fluorescein, have become also part of this armamentarium to localize the lesion and its boundaries peroperatively. Considering its alleged safety profile and its ability to diffuse in areas of altered blood-brain barrier, a typical characteristic of a number of both benign and malignant pediatric tumors, sodium fluorescein may appear an ideal candidate as intraoperative adjunct in pediatric neurosurgery. Nevertheless, a definitive role of this dye in children has not been established yet, and the reports on the pediatric population remain scarce. For this reason, we propose focusing on the use of sodium fluorescein in pediatric oncological neurosurgery by collecting articles reporting the result of the application of the technique in the management of intracranial pediatric tumors.

The Extent of Resection in Gliomas-Evidence-Based Recommendations on Methodological Aspects of Research Design

OBJECTIVE

Modern neurosurgery has established maximal safe resection as a cornerstone in the management of diffuse gliomas. Evaluation of the extent of resection (EOR), and its association with certain outcomes or interventions, heavily depends on an adequate methodology to draw strong conclusions. We aim to identify weaknesses and limitations that may threaten the internal validity and generalizability of studies involving the EOR in patients with glioma and to suggest methodological recommendations that may help mitigate these threats.

METHODS

A systematic search was performed by querying PubMed, Web of Science, and Scopus since inception to April 30, 2021 using PICOS/PRISMA guidelines. Articles were then screened to identify high-impact studies evaluating the EOR in patients diagnosed with diffuse gliomas in accordance with predefined criteria. We identify common weakness and limitations during the evaluation of the EOR in the selected studies and then delineate potential methodological recommendations for future endeavors dealing with the EOR.

RESULTS

We identified 31 high-impact studies and found several research design issues including inconsistencies regarding EOR terminology, measurement, data collection, analysis, and reporting. Although some of these issues were related to now outdated reporting standards, many were still present in recent publications and deserve attention in contemporary and future research.

CONCLUSIONS

There is a current need to focus more attention to the methodological aspects of glioma research. Methodological inconsistencies may introduce weaknesses into the internal validity of the studies and hamper comparative analysis of cohorts from different institutions. We hope our recommendations will eventually help develop stronger methodological designs in future research endeavors.

Accounting for intraoperative brain shift ascribable to cavity collapse during intracranial tumor resection

Purpose: For many patients with intracranial tumors, accurate surgical resection is a mainstay of their treatment paradigm. During surgical resection, image guidance is used to aid in localization and resection. Intraoperative brain shift can invalidate these guidance systems. One cause of intraoperative brain shift is cavity collapse due to tumor resection, which will be referred to as "debulking." We developed an imaging-driven finite element model of debulking to create a comprehensive simulation data set to reflect possible intraoperative changes. The objective was to create a method to account for brain shift due to debulking for applications in image-guided neurosurgery. We hypothesized that accounting for tumor debulking in a deformation atlas data framework would improve brain shift predictions, which would enhance image-based surgical guidance. Approach: This was evaluated in a six-patient intracranial tumor resection intraoperative data set. The brain shift deformation atlas data framework consisted of n = 756 simulated deformations to account for effects due to gravity-induced and hyperosmotic drug-induced brain shift, which reflects previous developments. An additional complement of n = 84 deformations involving simulated tumor growth followed by debulking was created to capture observed intraoperative effects not previously included. Results: In five of six patient cases evaluated, inclusion of debulking mechanics improved brain shift correction by capturing global mass effects resulting from the resected tumor. Conclusions: These findings suggest imaging-driven brain shift models used to create a deformation simulation data framework of observed intraoperative events can be used to assist in more accurate image-guided surgical navigation in the brain.

Liposomal Lapatinib in Combination with Low-Dose Photodynamic Therapy for the Treatment of Glioma

BACKGROUND

Malignant gliomas are highly invasive and extremely difficult to treat tumours with poor prognosis and outcomes. Photodynamic therapy (PDT), mediated by Gleolan®, has been studied previously with partial success in treating these tumours and extending lifetime. We aim to determine whether combining PDT using ALA-protoporphyrin IX (PpIX) with a liposomal formulation of the clinical epidermal growth factor receptor (EGFR) inhibitor, lapatinib, would increase the anti-tumour PDT efficacy.

METHODS

Lapatinib was given in vitro and in vivo 24 h prior to PDT and for 3-5 days following PDT to elicit whether the combination provided any benefits to PDT therapy. Live-cell imaging, in vitro PDT, and in vivo studies were performed to elucidate the effect lapatinib had on PDT for a variety of glioma cell lines and as well as GSC-30 neurospheres in vivo.

RESULTS

PDT combined with lapatinib led to a significant increase in PpIX accumulation, and reductions in the LD₅₀ of PpIX mediated PDT in two EGFR-driven cell lines, U87 and U87vIII, tested (p < 0.05). PDT + lapatinib elicited stronger MRI-quantified glioma responses following PDT for two human glioma-derived tumours (U87 and GSC-30) in vivo (p < 0.05). Furthermore, PDT leads to enhanced survival in rats following treatment with lapatinib compared to lapatinib alone and PDT alone (p < 0.05).

CONCLUSIONS

As lapatinib is approved for other oncological indications, a realization of its potential combination with PDT and in fluorescence-guided resection could be readily tested clinically. Furthermore, as its use would only be in acute settings, long-term resistance should not pose an issue as compared to its use as monotherapy.

Functional Change of Effector Tumor-Infiltrating CCR5+CD38+HLA-DR+CD8+ T Cells in Glioma Microenvironment

Human glioma facilitates an impaired anti-tumor immunity response, including defects in circulation of T lymphocytes. The level of CD8⁺ T-cell activation acts as an immune regulator associated with disease progression. However, little is known about the characteristics of peripheral and tumor-infiltrating CD8⁺ T cells in patients with glioma. In this study, we examined the level of CD8⁺ T-cell activation in a group of 143 patients with glioma and determined that peripheral CD3⁺ T cells decreased in accordance with disease severity. The patients' peripheral CD8⁺ T-cell populations were similar to that of healthy donors, and a small amount of CD8⁺ tumor-infiltrating lymphocytes was identified in glioma tissues. An increase in activated CD8⁺ T cells, characterized as CD38⁺HLA-DR⁺, and their association with disease progression were identified in the patients' peripheral blood and glioma, and shown to display enriched CCR5⁺ and TNFR2⁺ expression levels. Ex vivo examination of CD38⁺HLA-DR⁺CD8⁺ T cells indicated that this subset of cells displayed stronger secretion of IFN-γ and IL-2 before and after a 6-h stimulation with phorbol 12-myristate 13-acetate (PMA) and ionomycin (ION) relative to healthy CD38⁺HLA-DR⁺CD8⁺ T cells, indicating the functional feasibility of CD38⁺HLA-DR⁺CD8⁺ T cells. Higher CCL5 protein and mRNA levels were identified in glioma tissues, which was consistent with the immunohistochemistry results revealing both CCL5 and CD38⁺HLA-DR⁺CD8⁺ T cell expression. Patients' CCR5⁺CD38⁺HLA-DR⁺CD8⁺ T cells were further validated and shown to display increases in CD45RA⁺CCR7^- and T-bet⁺ accompanied by substantial CD107-a, IFN-γ, and Granzyme B levels in response to glioma cells.

Delta-Aminolevulinic Acid-Mediated Photodiagnoses in Surgical Oncology: A Historical Review of Clinical Trials

Fluorescence imaging is an emerging clinical technique for real-time intraoperative visualization of tumors and their boundaries. Though multiple fluorescent contrast agents are available in the basic sciences, few fluorescence agents are available for clinical use. Of the clinical fluorophores, delta aminolevulinic acid (5ALA) is unique for generating visible wavelength tumor-specific fluorescence. In 2017, 5ALA was FDA-approved for glioma surgery in the United States. Additionally, clinical studies suggest this agent may have utility in surgical subspecialties outside of neurosurgery. Data from dermatology, OB/GYN, urology, cardiothoracic surgery, and gastrointestinal surgery show 5ALA is helpful for intraoperative visualization of malignant tissues in multiple organ systems. This review summarizes data from English-language 5ALA clinical trials across surgical subspecialties. Imaging systems, routes of administration, dosing, efficacy, and related side effects are reviewed. We found that modified surgical microscopes and endoscopes are the preferred imaging devices. Systemic dosing across surgical specialties range between 5 and 30 mg/kg bodyweight. Multiple studies discussed potential for skin irritation with sun exposure, however this side effect is infrequently reported. Overall, 5ALA has shown high sensitivity for labeling malignant tissues and providing a means to visualize malignant tissue not apparent with standard operative light sources.

Established and emerging uses of 5-ALA in the brain: an overview

INTRODUCTION

5-aminolevulinic acid (5-ALA) was approved by the FDA in June 2017 as an intra-operative optical imaging agent for patients with gliomas (suspected World Health Organization Grades III or IV on preoperative imaging) as an adjunct for the visualization of malignant tissue during surgery. 5-ALA fluorescence-guided surgery (FGS) has been in widespread use in Europe and other continents since 2007.

METHODS

We reviewed the data available and summarize the most important known uses of 5-ALA FGS and its potential future applications.

RESULTS/CONCLUSIONS

The technique has been extensively studied, and more than 300 papers have been published on this topic. Visualization of high-grade glioma tissue is robust and reproducible, and can impact the extent of tumor resection and patient outcomes. 5-ALA FGS for other kind of tumors needs further development.

Various shades of red-a systematic analysis of qualitative estimation of ALA-derived fluorescence in neurosurgery

5-Aminolevulinic acid (5-ALA)-fluorescence-guided resection is well established in many neuro-oncologic centers. Different classifications of 5-ALA-induced fluorescence have been reported. The aim of the systematic analysis was to evaluate the frequency of graduations, definitions, and designations of 5-ALA-induced fluorescence qualities. A systematic database search of PubMed was performed to identify studies reporting (1) on 5-ALA fluorescence-guided either spinal or cranial surgery, (2) on qualitative estimation and/or categorization of 5-ALA-induced fluorescence, (3) in English, and (4) were published as peer-reviewed original studies. Totally, 93 studies were identified. Different classification systems of 5-ALA-induced fluorescence were found. Over 60 % of the included studies used a dichotomized categorization of 5-ALA-induced fluorescence and 27.5 % of studies distinguished two different intensities of 5-ALA fluorescent tissue in addition to non-fluorescing tissue. More than 50 % of studies explicitly defined criteria for categorization of 5-ALA-induced fluorescence. The major limitation of the present analysis might be that it mainly comprises data from retrospective, uncontrolled, non-randomized trials. However, a precise definition of each 5-ALA-induced fluorescence quality is essential. Although dichotomized classification is the most common and simple graduation system, it may not be suitable for every clinical or scientific task. A three-level 5-ALA-induced fluorescence classification with precise definition of each fluorescence quality and their correlation with histological features would be more useful and reproducible in these cases.

Comprehensive high-throughput image analysis for therapeutic efficacy of architecturally complex heterotypic organoids

Bioengineered three-dimensional (3D) tumor models that incorporate heterotypic cellular communication are gaining interest as they can recapitulate key features regarding the intrinsic heterogeneity of cancer tissues. However, the architectural complexity and heterogeneous contents associated with these models pose a challenge for toxicological assays to accurately report treatment outcomes. To address this issue, we describe a comprehensive image analysis procedure for structurally complex organotypic cultures (CALYPSO) applied to fluorescence-based assays to extract multiparametric readouts of treatment effects for heterotypic tumor cultures that enables advanced analyses. The capacity of this approach is exemplified on various 3D models including adherent/suspension, mono-/heterocellular cultures and several disease types. The subsequent analysis revealed specific morphological effects of oxaliplatin chemotherapy, radiotherapy, and photodynamic therapy. The procedure can be readily implemented in most laboratories to facilitate high-throughput toxicological screening of pharmaceutical agents and treatment regimens on organotypic cultures of human disease to expedite drug and therapy development.

Fluorescence image-guided neurosurgery

Surgery plays an important role in the management of high-grade gliomas (HGG) and imparts significant tumor-free and overall survival advantages. However HGG margins are often invisible, making their gross total resection (GTR) a difficult task. Hence intraoperative technology such as intraoperative fluorescence was a revolutionary discovery. A critical literature review revealed fluorescence improved the GTR of HGG from 36% using standard surgery to 74.5 and 84.4% using aminolevulinic acid (ALA) or fluorescein (FLCN), respectively. The differences between ALA-fluorescence image-guided neurosurgery (FIGS) and FLCN-FIGS in HGG were not statistically significant. However, the cost per quality added life years was US$16,218 and US$3181 for ALA-FIGS and FLCN-FIGS, respectively. Therefore, FIGS provided a reliable intraoperative tumor marker. Both ALA- and FLCN-FIGS significantly improved GTR and were cost-effective.

Awake Craniotomy for Tumor Resection: Further Optimizing Therapy of Brain Tumors

In recent years more and more data have emerged linking the most radical resection to prolonged survival in patients harboring brain tumors. Since total tumor resection could increase postoperative morbidity, many methods have been suggested to reduce the risk of postoperative neurological deficits: awake craniotomy with the possibility of continuous patient-surgeon communication is one of the possibilities of finding out how radical a tumor resection can possibly be without causing permanent harm to the patient.In 1994 we started to perform awake craniotomy for glioma resection. In 2005 the use of intraoperative high-field magnetic resonance imaging (MRI) was included in the standard tumor therapy protocol. Here we review our experience in performing awake surgery for gliomas, gained in 219 patients.Patient selection by the operating surgeon and a neuropsychologist is of primary importance: the patient should feel as if they are part of the surgical team fighting against the tumor. The patient will undergo extensive neuropsychological testing, functional MRI, and fiber tractography in order to define the relationship between the tumor and the functionally relevant brain areas. Attention needs to be given at which particular time during surgery the intraoperative MRI is performed. Results from part of our series (without and with ioMRI scan) are presented.

Auditory display for fluorescence-guided open brain tumor surgery

PURPOSE

Protoporphyrin (PpIX) fluorescence allows discrimination of tumor and normal brain tissue during neurosurgery. A handheld fluorescence (HHF) probe can be used for spectroscopic measurement of 5-ALA-induced PpIX to enable objective detection compared to visual evaluation of fluorescence. However, current technology requires that the surgeon either views the measured values on a screen or employs an assistant to verbally relay the values. An auditory feedback system was developed and evaluated for communicating measured fluorescence intensity values directly to the surgeon.

METHODS

The auditory display was programmed to map the values measured by the HHF probe to the playback of tones that represented three fluorescence intensity ranges and one error signal. Ten persons with no previous knowledge of the application took part in a laboratory evaluation. After a brief training period, participants performed measurements on a tray of 96 wells of liquid fluorescence phantom and verbally stated the perceived measurement values for each well. The latency and accuracy of the participants' verbal responses were recorded. The long-term memorization of sound function was evaluated in a second set of 10 participants 2-3 and 7-12 days after training.

RESULTS

The participants identified the played tone accurately for 98% of measurements after training. The median response time to verbally identify the played tones was 2 pulses. No correlation was found between the latency and accuracy of the responses, and no significant correlation with the musical proficiency of the participants was observed on the function responses. Responses for the memory test were 100% accurate.

CONCLUSION

The employed auditory display was shown to be intuitive, easy to learn and remember, fast to recognize, and accurate in providing users with measurements of fluorescence intensity or error signal. The results of this work establish a basis for implementing and further evaluating auditory displays in clinical scenarios involving fluorescence guidance and other areas for which categorized auditory display could be useful.

In vivo multimodal tumor imaging and photodynamic therapy with novel theranostic agents based on the porphyrazine framework-chelated gadolinium (III) cation

BACKGROUND

A promising strategy for cancer diagnosis and therapy is the development of an agent for multimodal imaging and treatment. In the present paper we report on two novel multifunctional agents prepared on the porphyrazine pigment platform using a gadolinium (III) cation chelated by red-fluorescent tetrapyrrole macrocycles (GdPz1 and GdPz2).

METHODS

Spectral and magnetic properties of the compounds were analyzed. Monitoring of GdPz1 and GdPz2 accumulation in the murine colon carcinoma CT26 was performed in vivo using fluorescence imaging and MRI. The photobleaching of GdPz1 or GdPz2 and tumor growth rate after photodynamic therapy (PDT) were assessed.

RESULTS

GdPz1 and GdPz2 demonstrated the selective accumulation in tumor that was indicated by higher fluorescence intensity in the tumor area in comparison with the normal tissues. The results of MRI in vivo showed that GdPz1 or GdPz2 provided significant contrast enhancement of the tumor in T1 MR images. PDT with GdPz2 resulted in ~20% decrease in fluorescence intensity of the compound and the inhibition of tumor growth.

CONCLUSIONS

We assessed the efficiency of two innovative Gd(III) cation-porphyrazine chelates as bimodal MR and fluorescent probes and photosensitizers for PDT and showed their potentials for tumor diagnostics and treatment.

GENERAL SIGNIFICANCE

Water-soluble structures simple in preparation and administration into the body represent special interest for theranostics of tumors. Novel porphyrazine macrocycles chelating a central gadolinium cation demonstrated a good prospect as effective multimodal agents, representing a new approach to MRI and fluorescence imaging guided PDT.

Combination of hand-held probe and microscopy for fluorescence guided surgery in the brain tumor marginal zone

BACKGROUND

Visualization of the tumor is crucial for differentiating malignant tissue from healthy brain during surgery, especially in the tumor marginal zone. The aim of the study was to introduce a fluorescence spectroscopy-based hand-held probe (HHF-probe) for tumor identification in combination with the fluorescence guided resection surgical microscope (FGR-microscope), and evaluate them in terms of diagnostic performance and practical aspects of fluorescence detection.

MATERIAL AND METHODS

Eighteen operations were performed on 16 patients with suspected high-grade glioma. The HHF-probe and the FGR-microscope were used for detection of protoporphyrin (PpIX) fluorescence induced by 5-aminolevulinic acid (5-ALA) and evaluated against histopathological analysis and visual grading done through the FGR-microscope by the surgeon. A ratio of PpIX fluorescence intensity to the autofluorescence intensity (fluorescence ratio) was used to quantify the spectra detected by the probe.

RESULTS

Fluorescence ratio medians (range 0 - 40) measured by the probe were related to the intensity of the fluorescence in the FGR-microscope, categorized as "none" (0.3, n=131), "weak" (1.6, n=34) and "strong" (5.4, n=28). Of 131 "none" points in the FGR-microscope, 88 (67%) exhibited fluorescence with the HHF-probe. For the tumor marginal zone, the area under the receiver operator characteristics (ROC) curve was 0.49 for the FGR-microscope and 0.65 for the HHF-probe.

CONCLUSIONS

The probe was integrated in the established routine of tumor resection using the FGR-microscope. The HHF-probe was superior to the FGR-microscope in sensitivity; it detected tumor remnants after debulking under the FGR-microscope. The combination of the HHF-probe and the FGR-microscope was beneficial especially in the tumor marginal zone.

Fluorescence intensity and bright spot analyses using a confocal microscope for photodynamic diagnosis of brain tumors

BACKGROUND

In photodynamic diagnosis using 5-aminolevulinic acid (5-ALA), discrimination between the tumor and normal tissue is very important for a precise resection. However, it is difficult to distinguish between infiltrating tumor and normal regions in the boundary area. In this study, fluorescent intensity and bright spot analyses using a confocal microscope is proposed for the precise discrimination between infiltrating tumor and normal regions.

METHODS

From the 5-ALA-resected brain tumor tissue, the red fluorescent and marginal regions were sliced for observation under a confocal microscope. Hematoxylin and eosin (H&E) staining were performed on serial slices of the same tissue. According to the pathological inspection of the H&E slides, the tumor and infiltrating and normal regions on confocal microscopy images were investigated. From the fluorescent intensity of the image pixels, a histogram of pixel number with the same fluorescent intensity was obtained. The fluorescent bright spot sizes and total number were compared between the marginal and normal regions.

RESULTS

The fluorescence intensity distribution and average intensity in the tumor were different from those in the normal region. The probability of a difference from the dark enhanced the difference between the tumor and the normal region. The bright spot size and number in the infiltrating tumor were different from those in the normal region.

CONCLUSIONS

Fluorescence intensity analysis is useful to distinguish a tumor region, and a bright spot analysis is useful to distinguish between infiltrating tumor and normal regions. These methods will be important for the precise resection or photodynamic therapy of brain tumors.

The effectiveness and cost-effectiveness of intraoperative imaging in high-grade glioma resection; a comparative review of intraoperative ALA, fluorescein, ultrasound and MRI

BACKGROUND

Surgical resection of high-grade gliomas (HGG) is standard therapy because it imparts significant progression free (PFS) and overall survival (OS). However, HGG-tumor margins are indistinguishable from normal brain during surgery. Hence intraoperative technology such as fluorescence (ALA, fluorescein) and intraoperative ultrasound (IoUS) and MRI (IoMRI) has been deployed. This study compares the effectiveness and cost-effectiveness of these technologies.

METHODS

Critical literature review and meta-analyses, using MEDLINE/PubMed service. The list of references in each article was double-checked for any missing references. We included all studies that reported the use of ALA, fluorescein (FLCN), IoUS or IoMRI to guide HGG-surgery. The meta-analyses were conducted according to statistical heterogeneity between studies. If there was no heterogeneity, fixed effects model was used; otherwise, a random effects model was used. Statistical heterogeneity was explored by χ² and inconsistency (I²) statistics. To assess cost-effectiveness, we calculated the incremental cost per quality-adjusted life-year (QALY).

RESULTS

Gross total resection (GTR) after ALA, FLCN, IoUS and IoMRI was 69.1%, 84.4%, 73.4% and 70% respectively. The differences were not statistically significant. All four techniques led to significant prolongation of PFS and tended to prolong OS. However none of these technologies led to significant prolongation of OS compared to controls. The cost/QALY was $16,218, $3181, $6049 and $32,954 for ALA, FLCN, IoUS and IoMRI respectively.

CONCLUSIONS

ALA, FLCN, IoUS and IoMRI significantly improve GTR and PFS of HGG. Their incremental cost was below the threshold for cost-effectiveness of HGG-therapy, denoting that each intraoperative technology was cost-effective on its own.

The role of 5-aminolevulinic acid in enhancing surgery for high-grade glioma, its current boundaries, and future perspectives: A systematic review

5-Aminolevulinic acid (5-ALA) has been approved as an intraoperative adjunct in glioma surgery in Europe, but not North America. A systematic review was conducted to assess the evidence regarding 5-ALA as a surgical adjunct. The MEDLINE, EMBASE, and CENTRAL databases were searched, using terms relevant to "5-ALA" and "high-grade gliomas." Included studies were based on adults aged ≥18 years who underwent surgical resection/biopsy. No language or date limitations were used. Forty-three studies (1830 patients) were identified. Thirty-six were coordinated by European countries, 2 were in the United States, and none were in Canada. One was randomized, 28 were prospective, and 14 were retrospective. Twenty-six studies assessed the utility of 5-ALA as a diagnostic tool, 24 assessed its influence on the extent of resection (EOR), 9 assessed survival, and 22 reported adverse events. 5-ALA had high sensitivity and positive predictive value, whereas its specificity increased with additional adjuncts. The EOR increased with 5-ALA, but only progression-free survival was significantly influenced. Reporting of adverse events was not systematic. The use of 5-ALA improved tumor visualization and thus enabled a greater EOR and perhaps increased survival. However, additional adjuncts may be necessary for maximizing the specificity of resection and patient safety. Additional parameters, such as patient quality of life and health economic analyses, would be informative. Thus, additional systematic collection of prospective evidence may be necessary for the global incorporation of this potentially valuable surgical adjunct into routine practice. Cancer 2016;122:2469-78. © 2016 American Cancer Society.

Intraoperative Ultrasound-Guided Resection of Gliomas: A Meta-Analysis and Review of the Literature

BACKGROUND

Image-guided surgery has become standard practice during surgical resection, using preoperative magnetic resonance imaging. Intraoperative ultrasound (IoUS) has attracted interest because of its perceived safety, portability, and real-time imaging. This report is a meta-analysis of intraoperative ultrasound in gliomas.

METHODS

Critical literature review and meta-analyses, using the MEDLINE/PubMed service. The list of references in each article was double-checked for any missing references. We included all studies that reported the use of ultrasound to guide glioma-surgery. The meta-analyses were conducted according to statistical heterogeneity between the studies using Open MetaAnalyst Software. If there was no heterogeneity, fixed effects model was used for meta-analysis; otherwise, a random effect model was used. Statistical heterogeneity was explored by χ(2) and inconsistency (I(2)) statistics; an I(2) value of 50% or more represented substantial heterogeneity.

RESULTS

A wide search yielded 19,109 studies that might be relevant, of which 4819 were ultrasound in neurosurgery; 756 studies used ultrasound in cranial surgery, of which 24 studies used intraoperative ultrasound to guide surgical resection and 74 studies used it to guide biopsy. Fifteen studies fulfilled our stringent inclusion criteria, giving a total of 739 patients. The estimated average gross total resection rate was 77%. Furthermore, the relationship between extent of surgical resection and study population was not linear. Gross total resection was more likely under IoUS when the lesion was solitary and subcortical, with no history of surgery or radiotherapy. IoUS image quality, sensitivity, specificity, and positive and negative predictive values deteriorated as surgical resection proceeded.

CONCLUSION

IoUS-guided surgical resection of gliomas is a useful tool for guiding the resection and for improving the extent of resection. IoUS can be used in conjunction with other complementary technologies that can improve anatomic orientation during surgery. Real-time imaging, improved image quality, small probe sizes, repeatability, portability, and relatively low cost make IoUS a realistic, cost-effective tool that complements any existing tools in any neurosurgical operating environment.

Effect of Metalation on Porphyrin-Based Bifunctional Agents in Tumor Imaging and Photodynamic Therapy

Herein we report the syntheses and comparative photophysical, electrochemical, in vitro, and in vivo biological efficacy of 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-cyanine dye (HPPH-CD) and the corresponding indium (In), gallium (Ga), and palladium (Pd) conjugates. The insertion of a heavy metal in the HPPH moiety makes a significant difference in FRET (Förster resonance energy transfer) and electrochemical properties, which correlates with singlet oxygen production [a key cytotoxic agent for photodynamic therapy (PDT)] and long-term in vivo PDT efficacy. Among the metalated analogs, the In(III) HPPH-CD showed the best cancer imaging and PDT efficacy. Interestingly, in contrast to free base HPPH-CD, which requires a significantly higher therapeutic dose (2.5 μmol/kg) than imaging dose (0.3 μmol/kg), the corresponding In(III) HPPH-CD showed excellent imaging and therapeutic potential at a remarkably low dose (0.3 μmol/kg) in BALB/c mice bearing Colon26 tumors. A comparative study of metalated and corresponding nonmetalated conjugates further confirmed that STAT-3 dimerization can be used as a biomarker for determining the level of photoreaction and tumor response.

The Art of Intraoperative Glioma Identification

A major dilemma in brain-tumor surgery is the identification of tumor boundaries to maximize tumor excision and minimize postoperative neurological damage. Gliomas, especially low-grade tumors, and normal brain have a similar color and texture, which poses a challenge to the neurosurgeon. Advances in glioma resection techniques combine the experience of the neurosurgeon and various advanced technologies. Intraoperative methods to delineate gliomas from normal tissue consist of (1) image-based navigation, (2) intraoperative sampling, (3) electrophysiological monitoring, and (4) enhanced visual tumor demarcation. The advantages and disadvantages of each technique are discussed. A combination of these methods is becoming widely accepted in routine glioma surgery. Gross total resection in conjunction with radiation, chemotherapy, or immune/gene therapy may increase the rates of cure in this devastating disease.

Impact of Substituents in Tumor Uptake and Fluorescence Imaging Ability of Near-Infrared Cyanine-like Dyes

This report presents a simple strategy to introduce various functionalities in a cyanine dye (bis-indole-N-butylsulfonate-polymethine bearing a fused cyclic chloro-cyclohexene ring structure), and assess the impact of these substitutions in tumor uptake, retention and imaging. The results obtained from the structural activity relationship (SAR) study demonstrate that certain structural features introduced in the cyanine dye moiety make a remarkable difference in tumor avidity. Among the compounds investigated, the symmetrical CDs containing an amino-phenyl thioether group attached to a cyclohexene ring system and the two N-butyl linkers with terminal sulfonate groups in benzoindole moieties exhibited excellent tumor imaging ability in BALB/c mice bearing Colon26 tumors. Compared to indocyanine green (ICG), approved by FDA as a blood pooling agent, which has also been investigated for the use in tumor imaging, the modified CD selected on the basis of SAR study produced enhanced uptake and longer retention in tumor(s). A facile approach reported herein for introducing a variety of functionalities in tumor-avid CD provides an opportunity to create multi-imaging modality agent(s). Using a combination of mass spectrometry and absorbance techniques, the photobleaching of one of the CDs was analyzed and significant regioselective photooxidation was observed.

Glioblastoma multiforme: emerging treatments and stratification markers beyond new drugs

Glioblastoma multiforme (GBM) is the most common primary brain tumour in adults. The standard therapy for GBM is maximal surgical resection followed by radiotherapy with concurrent and adjuvant temozolomide (TMZ). In spite of the extensive treatment, the disease is associated with poor clinical outcome. Further intensification of the standard treatment is limited by the infiltrating growth of the GBM in normal brain areas, the expected neurological toxicities with radiation doses >60 Gy and the dose-limiting toxicities induced by systemic therapy. To improve the outcome of patients with GBM, alternative treatment modalities which add low or no additional toxicities to the standard treatment are needed. Many Phase II trials on new chemotherapeutics or targeted drugs have indicated potential efficacy but failed to improve the overall or progression-free survival in Phase III clinical trials. In this review, we will discuss contemporary issues related to recent technical developments and new metabolic strategies for patients with GBM including MR (spectroscopy) imaging, (amino acid) positron emission tomography (PET), amino acid PET, surgery, radiogenomics, particle therapy, radioimmunotherapy and diets.

5-ALA Fluorescence Image Guided Resection of Glioblastoma Multiforme: A Meta-Analysis of the Literature

BACKGROUND

Glioblastoma multiforme (GBM) is one of the most deadly cancers in humans. Despite recent advances in anti-cancer therapies, most patients with GBM die from local disease progression. Fluorescence image guided surgical resection (FIGR) was recently advocated to enhance local control of GBM. This is meta-analyses of 5-aminolevulinic (5-ALA) induced FIGR.

MATERIALS

Review of the literature produced 503 potential publications; only 20 of these fulfilled the inclusion criteria of this analysis, including a total of 565 patients treated with 5-ALA-FIGR reporting on its outcomes and 800 histological samples reporting 5-ALA-FIGR sensitivity and specificity.

RESULTS

The mean gross total resection (GTR) rate was 75.4% (95% CI: 67.4-83.5, p<0.001). The mean time to tumor progression (TTP) was 8.1 months (95% CI: 4.7-12, p<0.001). The mean overall survival gain reported was 6.2 months (95% CI: -1-13, p<0.001). The specificity was 88.9% (95% CI: 83.9-93.9, p<0.001) and the sensitivity was 82.6% (95% CI: 73.9-91.9, p<0.001).

CONCLUSION

5-ALA-FIGR in GBM is highly sensitive and specific, and imparts significant benefits to patients in terms of improved GTR and TTP.

Colour contrasting between tissues predicts the resection in 5-aminolevulinic acid-guided surgery of malignant gliomas

Due to the various intensities of 5-aminolevulinic acid (5-ALA) fluorescence, neurosurgeons tend to be uncertain about which tissues to resect. This study aimed to reveal the shortcomings of the human visual perception of fluorescence, particularly the factors guiding the tissue removal and the correlation of fluorescence with contrast enhancement (CE) on magnetic resonance imaging (MRI). Various colour features [CIE L*a*b* colour space, colour difference described by ΔE and contrast ratio (CR)] of total 206 noticed fluorescent areas and their surroundings were measured from the video recordings of 21 primary high grade glioma (HGG) surgeries. The position of a fluorescent region was related to the corecorded navigational image. Following early postoperative MRI, 17 additional regions of corresponding to CE remnants were identified, their colour features were compared to the resected CEs. The targeted video post-processing method was designed, based on the results. There were no complications attributed to 5-ALA use and the median survival was <10 months. 82.5 % of recognised fluorescent areas were removed. Colour spaces of the resected regions and their backgrounds did not overlap. Opposite to the separate colour components (p > 0.05), the distant background colour (p < 0.05) and higher CR and ΔE (p < 0.01) determined the resection of a fluorescent region. Noneloquent location and CR both independently increased the resection rate in logistic regression. However, greater area under the receiver operating characteristic curve (AUC) in case of CR (AUC = 0.78; 95 % CI 0.71-0.83) determined its dominant role in neurosurgeon's fluorescence perception. CE regions presented with a significantly more saturated shade of violet (consistently higher a* and b*) than other tumour parts (p < 0.05). Regions corresponding to tumour remnants had a significantly lower a* component value (p = 0.02) as well as a lower ΔE than the matched background (AUC = 0.73; 95 % CI 0.65-0.80). In order to increase the resection rate, ΔE > 60 was needed. These results directed essential improvements in the 5-ALA fluorescence visualisation toward enhanced resection rate. The conventional filtering, unadjusted to the 5-ALA colour space converted some background shades to colours resembling relevant fluorescence. This is one of the first studies to demonstrate that perceived colours, their contrasting and CR are of significance in the decision-making during HGG 5-ALA fluorescence-guided surgery. Irrespective of the shortcomings of conventional video filtering, further development of a tailored post-processed contrast stretching will allow to achieve safe and radical tumour resection.

Protoporphyrin-IX fluorescence guided surgical resection in high-grade gliomas: The potential impact of human colour perception

INTRODUCTION

Protoporphyrin-IX (Pp-IX) fluorescence had been used frequently in recent years to guide microsurgical resection of high-grade gliomas (HGG), particularly following the publication of a randomized controlled trial demonstrating its advantages. However, Pp-IX fluorescence is dependent upon the surgeons' eyes' perception of red fluorescent colour. This study was designed to evaluate human eye fluorescence perception and establish a fluorescence scale.

MATERIALS AND METHODS

20 of 108 pre-recorded images from intraoperative fluorescence of HGG were used to construct an 8-panel visual analogue fluorescence scale. The scale was validated by testing 56 participants with normal colour vision and three red-green colour-blind participants. For intra-rater agreement ten participants were tested twice and for inter-observer reliability the whole cohort were tested.

RESULTS

The intra- and inter-observer reliability of the scale in normal colour vision participants was excellent. The scale was less reliable in the violet-blue panels of the scale. Colour-blind participants were not able to distinguish between red fluorescence and blue-violet colours.

CONCLUSION

The 8-panel fluorescence scale is valid in differentiating red, pink and blue colours in a fluorescence surgical field among participants with normal colour perception and potentially useful to standardize fluorescence-guided surgery. However, colourblind surgeons should not use fluorescence-guided surgery.