Intraoperative fluorescence-guided resection of high-grade gliomas: a comparison of the present techniques and evolution of future strategies

Towards machine learning-based quantitative hyperspectral image guidance for brain tumor resection

BACKGROUND

Complete resection of malignant gliomas is hampered by the difficulty in distinguishing tumor cells at the infiltration zone. Fluorescence guidance with 5-ALA assists in reaching this goal. Using hyperspectral imaging, previous work characterized five fluorophores' emission spectra in most human brain tumors.

METHODS

In this paper, the effectiveness of these five spectra was explored for different tumor and tissue classification tasks in 184 patients (891 hyperspectral measurements) harboring low- (n = 30) and high-grade gliomas (n = 115), non-glial primary brain tumors (n = 19), radiation necrosis (n = 2), miscellaneous (n = 10) and metastases (n = 8). Four machine-learning models were trained to classify tumor type, grade, glioma margins, and IDH mutation.

RESULTS

Using random forests and multilayer perceptrons, the classifiers achieve average test accuracies of 84-87%, 96.1%, 86%, and 91% respectively. All five fluorophore abundances vary between tumor margin types and tumor grades (p < 0.01). For tissue type, at least four of the five fluorophore abundances are significantly different (p < 0.01) between all classes.

CONCLUSIONS

These results demonstrate the fluorophores' differing abundances in different tissue classes and the value of the five fluorophores as potential optical biomarkers, opening new opportunities for intraoperative classification systems in fluorescence-guided neurosurgery.

Recurrent Glioblastoma-Molecular Underpinnings and Evolving Treatment Paradigms

Glioblastoma is the most common and lethal central nervous system malignancy with a median survival after progression of only 6-9 months. Major biochemical mechanisms implicated in glioblastoma recurrence include aberrant molecular pathways, a recurrence-inducing tumor microenvironment, and epigenetic modifications. Contemporary standard-of-care (surgery, radiation, chemotherapy, and tumor treating fields) helps to control the primary tumor but rarely prevents relapse. Cytoreductive treatment such as surgery has shown benefits in recurrent glioblastoma; however, its use remains controversial. Several innovative treatments are emerging for recurrent glioblastoma, including checkpoint inhibitors, chimeric antigen receptor T cell therapy, oncolytic virotherapy, nanoparticle delivery, laser interstitial thermal therapy, and photodynamic therapy. This review seeks to provide readers with an overview of (1) recent discoveries in the molecular basis of recurrence; (2) the role of surgery in treating recurrence; and (3) novel treatment paradigms emerging for recurrent glioblastoma.

Metabolic Insight into Glioma Heterogeneity: Mapping Whole Exome Sequencing to In Vivo Imaging with Stereotactic Localization and Deep Learning

Intratumoral heterogeneity (ITH) complicates the diagnosis and treatment of glioma, partly due to the diverse metabolic profiles driven by underlying genomic alterations. While multiparametric imaging enhances the characterization of ITH by capturing both spatial and functional variations, it falls short in directly assessing the metabolic activities that underpin these phenotypic differences. This gap stems from the challenge of integrating easily accessible, colocated pathology and detailed genomic data with metabolic insights. This study presents a multifaceted approach combining stereotactic biopsy with standard clinical open-craniotomy for sample collection, voxel-wise analysis of MR images, regression-based GAM, and whole-exome sequencing. This work aims to demonstrate the potential of machine learning algorithms to predict variations in cellular and molecular tumor characteristics. This retrospective study enrolled ten treatment-naïve patients with radiologically confirmed glioma. Each patient underwent a multiparametric MR scan (T1W, T1W-CE, T2W, T2W-FLAIR, DWI) prior to surgery. During standard craniotomy, at least 1 stereotactic biopsy was collected from each patient, with screenshots of the sample locations saved for spatial registration to pre-surgical MR data. Whole-exome sequencing was performed on flash-frozen tumor samples, prioritizing the signatures of five glioma-related genes: IDH1, TP53, EGFR, PIK3CA, and NF1. Regression was implemented with a GAM using a univariate shape function for each predictor. Standard receiver operating characteristic (ROC) analyses were used to evaluate detection, with AUC (area under curve) calculated for each gene target and MR contrast combination. Mean AUC for five gene targets and 31 MR contrast combinations was 0.75 ± 0.11; individual AUCs were as high as 0.96 for both IDH1 and TP53 with T2W-FLAIR and ADC, and 0.99 for EGFR with T2W and ADC. These results suggest the possibility of predicting exome-wide mutation events from noninvasive, in vivo imaging by combining stereotactic localization of glioma samples and a semi-parametric deep learning method. The genomic alterations identified, particularly in IDH1, TP53, EGFR, PIK3CA, and NF1, are known to play pivotal roles in metabolic pathways driving glioma heterogeneity. Our methodology, therefore, indirectly sheds light on the metabolic landscape of glioma through the lens of these critical genomic markers, suggesting a complex interplay between tumor genomics and metabolism. This approach holds potential for refining targeted therapy by better addressing the genomic heterogeneity of glioma tumors.

Predicting glioblastoma recurrence using multiparametric MR imaging of non-enhancing peritumoral regions at baseline

Background

To assess the feasibility of multiparametric magnetic resonance imaging in predicting tumor recurrence in nonenhancing peritumoral regions in patients with glioblastoma at baseline.

Methods

Fifty-eight patients with recurrent glioblastoma underwent multiparametric magnetic resonance imaging, including T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and dynamic susceptibility contrast perfusion-weighted imaging. Nonenhancing peritumoral regions with glioblastoma recurrence were identified by coregistering preoperative and post-recurrent magnetic resonance images. Regions of interest were placed in nonenhancing peritumoral regions with and without tumor recurrence to calculate the apparent diffusion coefficient value, and relative ratios of T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and cerebral blood volume values.

Results

Significant lower relative T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and relative apparent diffusion coefficient but higher relative cerebral blood volume values were found in the nonenhancing peritumoral regions with tumor recurrence than without recurrence (all P < 0.05). The threshold values ≥ 0.89 for relative cerebral blood volume provide the optimal performance for predicting the nonenhancing peritumoral regions with future tumor recurrence, with the sensitivity, specificity, and accuracy of 84.7%, 83.6%, and 85.8%, respectively. The combination of relative T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and relative cerebral blood volume can provide better predictive performance than relative cerebral blood volume (P = 0.015).

Conclusion

The combined use of T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and dynamic susceptibility contrast perfusion-weighted imaging can effectively estimate the risk of future tumor recurrence at baseline.

Automated online safety margin (GLIOVIS) for glioma surgery model

Purpose

Glioblastoma is the most common type of primary brain malignancy and has a poor prognosis. The standard treatment strategy is based on maximal safe surgical resection followed by radiotherapy and chemotherapy. Surgical resection can be optimized by using 5-delta-aminolevulinic acid (5-ALA)-induced fluorescence, which is the current mainstay. Although 5-ALA-induced fluorescence has gained general acceptance, it is also limited by inter-observer variability and non-standardized fluorescence parameters. We present a new software for processing images analysis to better recognize the tumor infiltration margins using an intraoperative immediate safety map of 5-ALA-induced fluorescence. We tested this in a brain model using a commercial surgical exoscope.

Methods

A dedicated software GLIOVIS (ACQuF-II, Advanced Colorimetry-based Quantification of Fluorescence) was designed for processing analysis of images taken on the Intraoperative Orbital Camera Olympus Orbeye (IOC) to determine the relative quantification of Protoporphyrin IX (5-ALA metabolite) fluorescence. The software allows to superpose the new fluorescence intensity map and the safety margins over the original images. The software was tested on gel-based brain models.

Results

Two surrogate models were developed: PpIX agarose gel-integrated in gelatin-based brain model at different scales (1:25 and 1:1). The images taken with the IOC were then processed using GLIOVIS. The intensity map and safety margins could be obtained for all available models.

Conclusions

GLIOVIS for 5-ALA-guided surgery image processing was validated on various gelatin-based brain models. Different levels of fluorescence could be qualitatively digitalized using this technique. These results need to be further confirmed and corroborated in vivo and validated clinically in order to define a new standard of care for glioblastoma resection.

5-ALA induced PpIX fluorescence spectroscopy in neurosurgery: a review

The review begins with an overview of the fundamental principles/physics underlying light, fluorescence, and other light-matter interactions in biological tissues. It then focuses on 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence spectroscopy methods used in neurosurgery (e.g., intensity, time-resolved) and in so doing, describe their specific features (e.g., hardware requirements, main processing methods) as well as their strengths and limitations. Finally, we review current clinical applications and future directions of 5-ALA-induced protoporphyrin IX (PpIX) fluorescence spectroscopy in neurosurgery.

Nanoparticles drug delivery for 5-aminolevulinic acid (5-ALA) in photodynamic therapy (PDT) for multiple cancer treatment: a critical review on biosynthesis, detection, and therapeutic applications

Photodynamic therapy (PDT) is a promising cancer treatment that kills cancer cells selectively by stimulating reactive oxygen species generation with photosensitizers exposed to specific light wavelengths. 5-aminolevulinic acid (5-ALA) is a widely used photosensitizer. However, its limited tumour penetration and targeting reduce its therapeutic efficacy. Scholars have investigated nano-delivery techniques to improve 5-ALA administration and efficacy in PDT. This review summarises recent advances in biological host biosynthetic pathways and regulatory mechanisms for 5-ALA production. The review also highlights the potential therapeutic efficacy of various 5-ALA nano-delivery modalities, such as nanoparticles, liposomes, and gels, in treating various cancers. Although promising, 5-ALA nano-delivery methods face challenges that could impair targeting and efficacy. To determine their safety and biocompatibility, extensive preclinical and clinical studies are required. This study highlights the potential of 5-ALA-NDSs to improve PDT for cancer treatment, as well as the need for additional research to overcome barriers and improve medical outcomes.

PiDeeL: metabolic pathway-informed deep learning model for survival analysis and pathological classification of gliomas

MOTIVATION

Online assessment of tumor characteristics during surgery is important and has the potential to establish an intra-operative surgeon feedback mechanism. With the availability of such feedback, surgeons could decide to be more liberal or conservative regarding the resection of the tumor. While there are methods to perform metabolomics-based tumor pathology prediction, their model complexity predictive performance is limited by the small dataset sizes. Furthermore, the information conveyed by the feedback provided on the tumor tissue could be improved both in terms of content and accuracy.

RESULTS

In this study, we propose a metabolic pathway-informed deep learning model (PiDeeL) to perform survival analysis and pathology assessment based on metabolite concentrations. We show that incorporating pathway information into the model architecture substantially reduces parameter complexity and achieves better survival analysis and pathological classification performance. With these design decisions, we show that PiDeeL improves tumor pathology prediction performance of the state-of-the-art in terms of the Area Under the ROC Curve by 3.38% and the Area Under the Precision-Recall Curve by 4.06%. Similarly, with respect to the time-dependent concordance index (c-index), PiDeeL achieves better survival analysis performance (improvement of 4.3%) when compared to the state-of-the-art. Moreover, we show that importance analyses performed on input metabolite features as well as pathway-specific neurons of PiDeeL provide insights into tumor metabolism. We foresee that the use of this model in the surgery room will help surgeons adjust the surgery plan on the fly and will result in better prognosis estimates tailored to surgical procedures.

AVAILABILITY AND IMPLEMENTATION

The code is released at https://github.com/ciceklab/PiDeeL. The data used in this study are released at https://zenodo.org/record/7228791.

How Reliable Is Fluorescence-Guided Surgery in Low-Grade Gliomas? A Systematic Review Concerning Different Fluorophores

BACKGROUND

Fluorescence-guided surgery has been increasingly used to support glioma surgery with the purpose of obtaining a maximal safe resection, in particular in high-grade gliomas, while its role is less definitely assessed in low-grade gliomas.

METHODS

A systematic review was conducted. 5-aminolevulinic acid, sodium fluorescein, indocyanine green and tozuleristide were taken into account. The main considered outcome was the fluorescence rate, defined as the number of patients in whom positive fluorescence was detected out of the total number of patients. Only low-grade gliomas were considered, and data were grouped according to single fluorophores.

RESULTS

16 papers about 5-aminolevulinic acid, 4 about sodium fluorescein, 2 about indocyanine green and 1 about tozuleristide were included in the systematic review. Regarding 5-aminolevulinic acid, a total of 467 low-grade glioma patients were included, and fluorescence positivity was detected in 34 out of 451 Grade II tumors (7.3%); while in Grade I tumors, fluorescence positivity was detected in 9 out of 16 cases. In 16 sodium fluorescein patients, seven positive fluorescent cases were detected. As far as indocyanine is concerned, two studies accounting for six patients (three positive) were included, while for tozuleristide, a single clinical trial with eight patients (two positive) was retrieved.

CONCLUSIONS

The current evidence does not support the routine use of 5-aminolevulinic acid or sodium fluorescein with a standard operating microscope because of the low fluorescence rates. New molecules, including tozuleristide, and new techniques for fluorescence detection have shown promising results; however, their use still needs to be clinically validated on a large scale.

Technical Pearls to Effectively Use 5-ALA in Fluorescence-Guided Tumor Resection—5 Lessons from the Operating Room

Background: Since its introduction in 2007 in Europe and in 2017 in the United States, 5-ALA has demonstrated an undisputed advantage in providing real-time tumor visualization. The aim of the present paper is to summarize our institutional experience over a decade of routine 5-ALA-guided procedures in order to provide five surgical tricks to ease surgical workflow. Methods: Data were collected from 822 patients diagnosed with histopathologically confirmed high-grade gliomas (HGG)—according to the WHO 2021 criteria—who underwent surgery at the Fondazione Policlinico Universitario Agostino Gemelli between January 2012 and January 2022. Results: From our large institutional experience, the learned technical pearls were grouped in five distinct domains: 1. Analysis of visualization, overall workflow, and technical recommendations to improve intraoperative set-up; 2. Techniques to reduce the risk of inadvertent residuals and failure to evocate fluorescence; 3. Analysis of specific surgical conditions favoring remnants; 4. Assessment of different degrees of fluorescence and their surgical meaning; 5. Analysis of false positive cases. Conclusions: With all the limitations of a qualitative and retrospective analysis, this paper was specifically conceived as a vademecum for educational purposes to promote and maximize 5-ALA employment.

Intraoperative Fluorescein Sodium in Pediatric Neurosurgery: A Preliminary Case Series from a Singapore Children’s Hospital

(1) Background: Fluorescein sodium (Na-Fl) has been described as a safe and useful neurosurgical adjunct in adult neurooncology. However, its use has yet to be fully established in children. We designed a study to investigate the use of intraoperative Na-Fl in pediatric brain tumor surgery. (2) Methods: This is a single-institution study for pediatric brain tumor patients managed by the Neurosurgical Service, KK Women’s and Children’s Hospital. Inclusion criteria consists of patients undergoing surgery for suspected brain tumors from 3 to 19 years old. A predefined intravenous dose of 2 mg/kg of 10% Na-Fl is administered per patient. Following craniotomy, surgery is performed under alternating white light and YELLOW-560 nm filter illumination. (3) Results: A total of 21 patients with suspected brain tumours were included. Median age was 12.1 years old. For three patients (14.3%), there was no significant Na-Fl fluorescence detected and their final histologies reported a cavernoma and two radiation-induced high grade gliomas. The remaining patients (85.7%) had adequate intraoperative fluorescence for their lesions. No adverse side effects were encountered with the use of Na-Fl. (4) Conclusions: Preliminary findings demonstrate the safe and efficacious use of intraoperative Na-Fl for brain tumors as a neurosurgical adjunct in our pediatric patients.

The Conventional Dendritic Cell 1 Subset Primes CD8+ T Cells and Traffics Tumor Antigen to Drive Antitumor Immunity in the Brain

The central nervous system (CNS) antigen-presenting cell (APC) that primes antitumor CD8+ T-cell responses remains undefined. Elsewhere in the body, the conventional dendritic cell 1 (cDC1) performs this role. However, steady-state brain parenchyma cDC1 are extremely rare; cDCs localize to the choroid plexus and dura. Thus, whether the cDC1 play a function in presenting antigen derived from parenchymal sources in the tumor setting remains unknown. Using preclinical glioblastoma (GBM) models and cDC1-deficient mice, we explored the presently unknown role of cDC1 in CNS antitumor immunity. We determined that, in addition to infiltrating the brain tumor parenchyma itself, cDC1 prime neoantigen-specific CD8+ T cells against brain tumors and mediate checkpoint blockade-induced survival benefit. We observed that cDC, including cDC1, isolated from the tumor, the dura, and the CNS-draining cervical lymph nodes harbored a traceable fluorescent tumor antigen. In patient samples, we observed several APC subsets (including the CD141+ cDC1 equivalent) infiltrating glioblastomas, meningiomas, and dura. In these same APC subsets, we identified a tumor-specific fluorescent metabolite of 5-aminolevulinic acid, which fluorescently labeled tumor cells during fluorescence-guided GBM resection. Together, these data elucidate the specialized behavior of cDC1 and suggest that cDC1 play a significant role in CNS antitumor immunity.

Review of Intraoperative Adjuncts for Maximal Safe Resection of Gliomas and Its Impact on Outcomes

Maximal safe resection is the mainstay of treatment in the neurosurgical management of gliomas, and preserving functional integrity is linked to favorable outcomes. How these modalities differ in their effectiveness on the extent of resection (EOR), survival, and complications remains unknown. A systematic literature search was performed with the following inclusion criteria: published between 2005 and 2022, involving brain glioma surgery, and including one or a combination of intraoperative modalities: intraoperative magnetic resonance imaging (iMRI), awake/general anesthesia craniotomy mapping (AC/GA), fluorescence-guided imaging, or combined modalities. Of 525 articles, 464 were excluded and 61 articles were included, involving 5221 glioma patients, 7(11.4%) articles used iMRI, 21(36.8%) used cortical mapping, 15(24.5%) used 5-aminolevulinic acid (5-ALA) or fluorescein sodium, and 18(29.5%) used combined modalities. The heterogeneity in reporting the amount of surgical resection prevented further analysis. Progression-free survival/overall survival (PFS/OS) were reported in 18/61(29.5%) articles, while complications and permanent disability were reported in 38/61(62.2%) articles. The reviewed studies demonstrate that intraoperative adjuncts such as iMRI, AC/GA mapping, fluorescence-guided imaging, and a combination of these modalities improve EOR. However, PFS/OS were underreported. Combining multiple intraoperative modalities seems to have the highest effect compared to each adjunct alone.

Synthesis and application of the fluorescent furan and imidazole probes for selective in vivo and in vitro cancer cell imaging

Development of imaging probes for identification of tumors in the early stages of growth can significantly reduce the tumor-related health hazards and improve our capacity for treatment of cancer. In this work, three different furan and imidazole fluorescent derivatives abbreviated as Cyclo X, SAC and SNO are introduced for in vivo and in vitro imaging of cancer cells. The fluorescence quantum yield values were 0.226, 0.400 and 0.479 for Cyclo X, SAC and SNO, respectively. The excitation and emission wavelengths of maximum intensity were (360, 452), (350, 428) and (350, 432) nm for Cyclo X, SAC and SNO, respectively. The MTT reduction assay was used to estimate the cytotoxic activity of the proposed derivatives against HT-29 (cancer) and Vero (normal) cell lines. Cyclo X showed no cytotoxic effect, while SAC and SNO showed significantly higher cytotoxicity against the tested cell lines than cisplatin as a well-known anticancer drug. In vitro fluorescence microscopic images obtained using HT-29 cells showed that Cyclo X produced very bright images. The in vivo cancer cell imaging using 4T1 tumor-bearing mice revealed that Cyclo X is selectively accumulated in the tumor without distribution in the mice body organs. The spectral and structural stability, large Stokes shift, non-cytotoxicity and high level of selectivity for in vivo imaging are properties that make Cyclo X a suitable candidate to be used for long-term monitoring of cancer cells.

Characterization of ex vivo and in vivo intraoperative neurosurgical confocal laser endomicroscopy imaging

Background

The new US Food and Drug Administration-cleared fluorescein sodium (FNa)-based confocal laser endomicroscopy (CLE) imaging system allows for intraoperative on-the-fly cellular level imaging. Two feasibility studies have been completed with intraoperative use of this CLE system in ex vivo and in vivo modalities. This study quantitatively compares the image quality and diagnostic performance of ex vivo and in vivo CLE imaging.

Methods

Images acquired from two prospective CLE clinical studies, one ex vivo and one in vivo, were analyzed quantitatively. Two image quality parameters – brightness and contrast – were measured using Fiji software and compared between ex vivo and in vivo images for imaging timing from FNa dose and in glioma, meningioma, and intracranial metastatic tumor cases. The diagnostic performance of the two studies was compared.

Results

Overall, the in vivo images have higher brightness and contrast than the ex vivo images (p < 0.001). A weak negative correlation exists between image quality and timing of imaging after FNa dose for the ex vivo images, but not the in vivo images. In vivo images have higher image quality than ex vivo images (p < 0.001) in glioma, meningioma, and intracranial metastatic tumor cases. In vivo imaging yielded higher sensitivity and negative predictive value than ex vivo imaging.

Conclusions

In our setting, in vivo CLE optical biopsy outperforms ex vivo CLE by producing higher quality images and less image deterioration, leading to better diagnostic performance. These results support the in vivo modality as the modality of choice for intraoperative CLE imaging.

Targeted metabolomics analyses for brain tumor margin assessment during surgery

MOTIVATION

Identification and removal of micro-scale residual tumor tissue during brain tumor surgery are key for survival in glioma patients. For this goal, High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HRMAS NMR) spectroscopy-based assessment of tumor margins during surgery has been an effective method. However, the time required for metabolite quantification and the need for human experts such as a pathologist to be present during surgery are major bottlenecks of this technique. While machine learning techniques that analyze the NMR spectrum in an untargeted manner (i.e. using the full raw signal) have been shown to effectively automate this feedback mechanism, high dimensional and noisy structure of the NMR signal limits the attained performance.

RESULTS

In this study, we show that identifying informative regions in the HRMAS NMR spectrum and using them for tumor margin assessment improves the prediction power. We use the spectra normalized with the ERETIC (electronic reference to access in vivo concentrations) method which uses an external reference signal to calibrate the HRMAS NMR spectrum. We train models to predict quantities of metabolites from annotated regions of this spectrum. Using these predictions for tumor margin assessment provides performance improvements up to 4.6% the Area Under the ROC Curve (AUC-ROC) and 2.8% the Area Under the Precision-Recall Curve (AUC-PR). We validate the importance of various tumor biomarkers and identify a novel region between 7.97 ppm and 8.09 ppm as a new candidate for a glioma biomarker.

AVAILABILITY AND IMPLEMENTATION

The code is released at https://github.com/ciceklab/targeted_brain_tumor_margin_assessment. The data underlying this article are available in Zenodo, at https://doi.org/10.5281/zenodo.5781769.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Sentinel lymph node detection by combining nonradioactive techniques with contrast agents: State of the art and prospects

The status of sentinel lymph nodes (SLNs) has a substantial prognostic value because these nodes are the first place where cancer cells accumulate along their spreading route. Routine SLN biopsy ("gold standard") involves peritumoral injections of radiopharmaceuticals, such as technetium-99m, which has obvious disadvantages. This review examines the methods used as "gold standard" analogs to diagnose SLNs. Nonradioactive preoperative and intraoperative methods of SLN detection are analyzed. Promising photonic tools for SLNs detection are reviewed, including NIR-I/NIR-II fluorescence imaging, photoswitching dyes for SLN detection, in vivo photoacoustic detection, imaging and biopsy of SLNs. Also are discussed methods of SLN detection by magnetic resonance imaging, ultrasonic imaging systems including as combined with photoacoustic imaging, and methods based on the magnetometer-aided detection of superparamagnetic nanoparticles. The advantages and disadvantages of nonradioactive SLN-detection methods are shown. The review concludes with prospects for the use of conservative diagnostic methods in combination with photonic tools.

Characterization of autofluorescence and quantitative protoporphyrin IX biomarkers for optical spectroscopy-guided glioma surgery

5-Aminolevulinic acid (5-ALA)-mediated fluorescence does not effectively depict low grade gliomas (LGG) or the infiltrative tumor portion of high-grade gliomas (HGG). While spectroscopy improves sensitivity and precision, this is currently limited by autofluorescence and a second protoporphyrin IX (PpIX) fluorescence state at 620 nm. We investigated the autofluorescence to better characterize the present spectra and thus increase PpIX quantification precision and sensitivity. This study included 128 patients undergoing surgery for malignant glioma. 5-ALA (Gliolan) was administered before anesthesia, and fluorescence was measured using a hyperspectral device. It was found that all 2692 measured spectra consisted of contributions from 620 to 634 nm PpIX, NADH, lipofuscin, and flavins. The basis spectra were characterized and their use in spectral unmixing led to 82.4% lower fitting error for weakly fluorescing areas (p < 0.001), and 92.3% fewer false positive tumor identifications in control measurements (p = 0.0065) compared to previous works. They also decreased the PpIX₆₂₀ contribution, thus halving the mean Ratio_620/634 (p < 0.001). The ratio was approximately 0 for HGGs and increasing for LGGs, as demonstrated previously. Additionally, the Ratio_620/634, the MIB-1/Ki-67 proliferation index, and the PpIX peak blue-shift were found to be significantly related to WHO grade, fluorescence visibility, and PpIX contribution (p < 0.001), and the value of these three as quantitative biomarkers is discussed.

Re-irradiation for high-grade gliomas: Has anything changed?

Optimal management after recurrence or progression of high-grade gliomas is still undefined and remains a challenge for neuro-oncology multidisciplinary teams. Improved radiation therapy techniques, new imaging methods, published experience, and a better radiobiological knowledge of brain tissue have positioned re-irradiation (re-RT) as an option for many of these patients. Decisions must be individualized, taking into account the pattern of relapse, previous treatment, and functional status, as well as the patient’s preferences and expected quality of life. Many questions remain unanswered with respect to re-RT: Who is the most appropriate candidate, which dose and fractionation are most effective, how to define the target volume, which imaging technique is best for planning, and what is the optimal timing? This review will focus on describing the most relevant studies that include re-RT as salvage therapy, with the aim of simplifying decision-making and designing the best available therapeutic strategy.

Clinical relevance of tumor consistency in pituitary adenoma

PURPOSE

To review the clinical relevance of pituitary adenoma (PA) consistency and its relationship to clinical presentation, radiologic and histopathological characteristics, and surgical outcomes.

BACKGROUND

PA consistency is a critical factor influencing operative planning, surgical outcomes, and patient counseling. There is no validated classification of PA consistency in the literature, and there are no current preoperative variables capable of predicting it.

REVIEW

We conducted a thorough literature review of the Medline, Embase, Web of Science, and Cochrane Library databases. The inclusion criteria were all articles that described PA consistency and correlated it with preoperative aspects, radiological, pathological, and operative findings, or clinical outcomes.

DISCUSSION

Although most authors differentiate easily aspirated (soft) tumors from those that are not (fibrous, might require prior fragmentation), there is no universally accepted PA consistency classification. Fibrous PA tends to be hypointense on T2WI and has lower apparent diffusion coefficient (ADC) values. Fibrous tumors seemed to present higher invasion into neighboring structures, including the cavernous sinus. Several articles suggest that dopamine agonists could increase PA consistency and that prior surgery and radiotherapy also make PA more fibrous. The anatomopathological studies identify collagen as being mainly responsible for fibrous consistency of adenomas.

CONCLUSIONS

Preoperative knowledge of PA consistency affords the neurosurgeon substantial benefit, which clearly appears to be relevant to surgical planning, risks, and surgery outcomes. It could also encourage the centralization of these high complexity tumors in reference centers. Further studies may be enhanced by applying standard consistency classification of the PA and analyzing a more extensive and prospective series of fibrous PA.

Supratentorial high-grade gliomas: maximal safe anatomical resection guided by augmented reality high-definition fiber tractography and fluorescein

OBJECTIVE

The theoretical advantages of augmented reality (AR) with diffusion tensor imaging (DTI)-based high-definition fiber tractography (HDFT) and sodium fluorescein (F) in high-grade glioma (HGG) surgery have not been investigated in detail. In this study, the authors aimed to evaluate the safety and efficacy profiles of HDFT-F microscope-based AR cytoreductive surgery for newly diagnosed supratentorial HGGs.

METHODS

Data of patients with newly diagnosed supratentorial HGGs who underwent surgery using the AR HDFT-F technique were reviewed and compared with those of a cohort of patients who underwent conventional white-light surgery assisted by infrared neuronavigation. The safety and efficacy of the techniques were reported based on the postoperative Neurological Assessment in Neuro-Oncology (NANO) scores, extent of resection (EOR), and Kaplan-Meier curves, respectively. The chi-square test was conducted for categorical variables. A p value < 0.05 was considered statistically significant.

RESULTS

A total of 54 patients underwent surgery using the AR HDFT-F technique, and 63 underwent conventional white-light surgery assisted by infrared neuronavigation. The mean postoperative NANO scores were 3.8 ± 2 and 5.2 ± 4 in the AR HDFT-F group and control group, respectively (p < 0.05). The EOR was higher in the AR HDFT-F group (p < 0.05) than in the control group. With a mean follow-up of 12.2 months, the rate of progression-free survival (PFS) was longer in the study group (log-rank test, p = 0.006) than in the control group. Moreover, the complication rates were 9.2% and 9.5% in the study and control groups, respectively.

CONCLUSIONS

Overall, AR HDFT-F-assisted surgery is safe and effective in maximizing the EOR and PFS rate for patients with newly diagnosed supratentorial HGGs, and in optimizing patient functional outcomes.

Resection of intra- and paraventricular malignant brain tumors using fluorescein sodium-guided neuroendoscopic transtubular approach

BACKGROUND

The requirement of brain retraction and difficulty in distinguishing the tumor demarcation are challenging in conventional approaches to intra- and paraventricular malignant tumors (IV-PVMTs). Tubular retractors can minimize the retraction injury, and fluorescein-guided (FG) surgery may promote the resection of tumors. Our aim is to evaluate the feasibility, safety, and effectiveness of fluorescein-guided endoscopic transtubular surgery for the resection of IV-PVMTs.

METHODS

Twenty patients with IV-PVMTs underwent FG endoscopic transtubular tumor resection. Fluorescein sodium was administered before the dural opening. The intraoperative fluorescence staining was classified as "helpful" and "unhelpful" based on surgical observation. Extent of resection was assessed using postoperative magnetic resonance imaging. Karnofsky Performance Status (KPS) score was used to evaluate the general physical condition of patients.

RESULTS

There were 9 glioblastomas, 4 anaplastic astrocytomas and 7 metastatic tumors. "Helpful" fluorescence staining was observed in 16(80%) of 20 patients. Gross total resection was achieved in 16(80%) cases, near-total in 3(15%) cases, and subtotal in 1 (5%) case. No intra- or postoperative complications related to the fluorescein sodium occurred. The median preoperative KPS score was 83, and the median KPS score 3-month after surgery was 88.

CONCLUSION

FG endoscopic transtubular surgery is a feasible technique for the resection of IV-PVMTs. It may be a safe and effective option for patients with these tumors. Future prospective randomized studies with larger samples are needed to confirm these preliminary data.

Extent of resection and survival in patients with glioblastoma multiforme: Systematic review and meta-analysis

BACKGROUND

Glioblastoma multiforme (GBM) owes an ominous prognosis: its mean overall survival is 14 months. The extent of surgical resection (ESR) highlights among factors in which an association has been found to a somewhat better prognosis. However, the association between greater ESR and prolonged overall (OS) survival is not a constant finding nor a proven cause-and-effect phenomenon. To our objective is to establish the strength of association between ESR and OS in patients with GBM through a systematic review and meta-analysis.

METHODS

In accordance with PRISMA-P recommendations, we conducted a systematic literature search; we included studies with adult patients who had undergone craniotomy for GBM. Our primary outcome is overall postoperative survival at 12 and 24 months. We reviewed 180 studies, excluded 158, and eliminated 8; 14 studies that suited our requirements were analyzed.

RESULTS

The initial level of evidence of all studies is low, and it may be degraded to very low according to GRADE criteria because of design issues. The definition of different levels of the extent of resection is heterogeneous and poorly defined. We found a great amount of variation in the methodology of the operation and the adjuvant treatment protocol. The combined result for relative risk (RR) for OS for 12 months analysis is 1.25 [95% confidence interval (95% CI) 1.14-1.36, P < .01], absolute risk reduction (ARR) of 15.7% (95% CI 11.9-19.4), relative risk reduction (RRR) of 0.24 (95% CI 0.18-0.31), number needed to treat (NNT) 6; for 24-month analysis RR is 1.59 (95% CI 1.11-2.26, P < .01) ARR of 11.5% (95% CI 7.7-15.1), relative risk reduction (RRR) of 0.53 (95% CI 0.33-0.76), (NNT) 9. In each term analysis, the proportion of alive patients who underwent more extensive resection is significantly higher than those who underwent subtotal resection.

CONCLUSION

Our results sustain a weak but statistically significant association between the ESR and OS in patients with GBM obtained from observational studies with a very low level of evidence according to GRADE criteria. As a consequence, any estimate of effect is very uncertain. Current information cannot sustain a cause-and-effect relationship between these variables.

Sodium Fluorescein-Guided Gross Total Resection of Pediatric Exophytic Brainstem Glioma: 2-Dimensional Operative Video

Brainstem gliomas comprise 10% to 20% of pediatric intracranial tumors.1 Gross total resection is associated with the greatest long-term survival.1 However, due to the eloquence of surrounding brain tissue, an aggressive resection is not always achievable and can be associated with significant risk.2 Sodium fluorescein can be used to help differentiate between tumor and normal tissue.3,4 In this operative video, we demonstrate the step-by-step technique to utilize fluorescence in surgically resecting an exophytic glioma arising from the midbrain in a 16-yr-old male. Technical nuances are highlighted in this operative video, including the use of the YELLOW 560 (Zeiss) filter to differentiate fluorescent tumor from normal tissue as well as strategic splitting of the tentorium to expose the supratentorial component of the tumor. A decrease in motor potentials of the right leg during the case did not translate into neurological worsening postoperatively; at 3-mo follow-up, the patient attests to better strength and coordination on his affected side. In summary, sodium fluorescein can be used as a critical adjunctive tool for successful surgery in the case of a brainstem tumor. Alternatives to this procedure included gross total resection with 5-aminolevulinic acid, subtotal resection with chemotherapy, and active monitoring, but were not chosen due to their limitations in this clinical case.5-7  Appropriate patient consent was obtained to perform this procedure and present this clinical case and surgical video for academic purposes.

The utilization of sodium fluorescein in pediatric brain stem gliomas: a case report and review of the literature

INTRODUCTION

A major challenge in the surgical resection of brainstem tumors is distinguishing tumor from normal tissue. One approach for addressing this problem is the use of fluorescent tracers such as sodium fluorescein (NaFl). NaFl disseminates through a disruption in the blood-brain barrier (BBB) and accumulates in the extracellular space of brain tumors. Intraoperative fluorescence microscopy can be performed to identify tumor tissue and avoid damage to adjacent, normal tissue. Here, we present the case of a 16-year-old male who underwent a left retrosigmoid craniotomy with splitting of the tentorium to remove a large exophytic brainstem tumor involving the cerebellar peduncle and with superior extension into the midbrain and thalamus.

OBJECTIVES

The primary objective of this study was to investigate the effectiveness of sodium fluorescein as an intraoperative technique and evaluate its potential benefit for resection of tumors in eloquent regions in the pediatric population. To do so, we focused on a case study approach; however, we also performed a literature review and evaluated different intraoperative fluorescent techniques and their benefits for tumor resection.

METHODS

We performed a literature search using PubMed and Google Scholar by the key words "sodium fluorescein," "brain stem tumor," and "central nervous system neoplasms." Twenty-nine articles including both pediatric and adult populations were selected for analysis and qualitative review.

RESULTS

In this case study, sodium fluorescein helped the surgeons to identify and obtain a gross total resection of a large brainstem tumor. The marker was especially helpful for discerning the inferior pole of the tumor buried inconspicuously in cerebellar tissue. We evaluate different fluorescent tracers, 5-ALA and ICG, and discuss their application and benefits in tumor resection surgery. We present different cases that found sodium fluorescein to be helpful in achieving a gross total resection.

CONCLUSION

The application of sodium fluorescein proved to be a safe and effective technique for the resection of brain stem tumors as shown in this case study. It helped to expose concealed areas and illuminate the tumor capsule. Further studies should test the clinical use of sodium fluorescein on brain stem tumor resection.

5-Aminolevulinic acid-guided resection improves the overall survival of patients with glioblastoma-a comparative cohort study of 343 patients

Background

5-Aminolevulic acid-guided surgery (5-ALA-GS) improves the extent of resection (EoR) and progression-free survival in patients with glioblastoma multiforme (GBM).

Methods

A single-center retrospective cohort study of adult patients with GBM who had surgical resection between 2013 and 2019, 5-ALA guided versus a non-5-ALA cohort. The primary outcome was the overall survival (OS). Secondary outcomes were EoR, performance status (PS), and new focal neurological deficit.

Results

Three hundred and forty-three patients were included: 253 patients in 5-ALA-GS group and 90 patients in the non-5-ALA-GS group. The OS (17.47 vs 10.63 months, P < .0001), postoperative PS (P < .0001), PS at 6 months (P = .002), new focal neurological deficit (23.3% vs 44.9%, P < .0001), and radiological EoR (gross total resection [GTR]-47.4% vs 22.9%, P < .0001) were significantly better in the 5-ALA-GS group compared to non-5-ALA-GS group. In multivariate analysis, use of 5-ALA (P = .003) and MGMT promoter methylation (P = .001) were significantly related with a better OS. In patients with radiological GTR, OS was also significantly better (P < .0001) in the 5-ALA-GS group compared to the non-5-ALA-GS group.

Conclusions

5-ALA-GS is associated with a significant improvement in the OS, PS after surgery and at 6 months, larger EoR, and fewer new motor deficits in patients with GBM.

Re-irradiation of recurrent glioblastoma using helical TomoTherapy with simultaneous integrated boost: preliminary considerations of treatment efficacy

Although there is still no standard treatment for recurrent glioblastoma multiforme (rGBM), re-irradiation could be a therapeutic option. We retrospectively evaluated the efficacy and safety of re-irradiation using helical TomoTherapy (HT) with a simultaneous integrated boost (SIB) technique in patients with rGBM. 24 patients with rGBM underwent HT-SIB. A total dose of 20 Gy was prescribed to the Flair (fluid-attenuated inversion recovery) planning tumor volume (PTV) and 25 Gy to the PTV-boost (T1 MRI contrast enhanced area) in 5 daily fractions to the isodose of 67% (maximum dose within the PTV-boost was 37.5 Gy). Toxicity was evaluated by converting the 3D-dose distribution to the equivalent dose in 2 Gy fractions on a voxel-by-voxel basis. Median follow-up after re-irradiation was 27.8 months (range 1.6-88.5 months). Median progression-free survival (PFS) was 4 months (95% CI 2.0-7.9 months), while 6-month PFS was 41.7% (95% CI 22.2-60.1 months). Median overall survival following re-irradiation was 10.7 months (95% CI 7.4-16.1 months). There were no cases of re-operation due to early or late toxicity. Our preliminary results suggest that helical TomoTherapy with the proposed SIB technique is a safe and feasible treatment option for patients with rGBM, including those large disease volumes, reducing toxicity.

Machine learning assisted intraoperative assessment of brain tumor margins using HRMAS NMR spectroscopy

Complete resection of the tumor is important for survival in glioma patients. Even if the gross total resection was achieved, left-over micro-scale tissue in the excision cavity risks recurrence. High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HRMAS NMR) technique can distinguish healthy and malign tissue efficiently using peak intensities of biomarker metabolites. The method is fast, sensitive and can work with small and unprocessed samples, which makes it a good fit for real-time analysis during surgery. However, only a targeted analysis for the existence of known tumor biomarkers can be made and this requires a technician with chemistry background, and a pathologist with knowledge on tumor metabolism to be present during surgery. Here, we show that we can accurately perform this analysis in real-time and can analyze the full spectrum in an untargeted fashion using machine learning. We work on a new and large HRMAS NMR dataset of glioma and control samples (n = 565), which are also labeled with a quantitative pathology analysis. Our results show that a random forest based approach can distinguish samples with tumor cells and controls accurately and effectively with a median AUC of 85.6% and AUPR of 93.4%. We also show that we can further distinguish benign and malignant samples with a median AUC of 87.1% and AUPR of 96.1%. We analyze the feature (peak) importance for classification to interpret the results of the classifier. We validate that known malignancy biomarkers such as creatine and 2-hydroxyglutarate play an important role in distinguishing tumor and normal cells and suggest new biomarker regions. The code is released at http://github.com/ciceklab/HRMAS_NC.

The Supraorbital Eyebrow Craniotomy for Intra- and Extra-Axial Brain Tumors: A Single-Center Series and Technique Modification

BACKGROUND

The supraorbital (SO) eyebrow craniotomy provides minimally invasive access to the anterior and middle fossae and parasellar region.

OBJECTIVE

To present a series of patients treated with the SO approach to assess outcomes, the impact of endoscopy, and describe a modified pericranial flap aimed at reducing postoperative frontalis paresis and hypesthesia.

METHODS

A retrospective analysis was undertaken of our prospective database of patients who underwent SO craniotomy for tumor/cyst removal. Patients were evaluated based on pathology, utility of endoscopy, extent of resection, complications, and functional/esthetic recovery.

RESULTS

From 2007 to 2018, 129 operations were performed in 117 patients (54% women; mean age 60 ± 16.5 yr). The most common lesions were meningiomas (43%), gliomas (15%), and metastases (15%). Prior surgery and/or radiation had been performed in 37% and 26% of patients, respectively. Endoscopy was used in 76 (61%) operations and allowed more complete tumor removal in 38 (50%). For first-time operations, gross-total removal was achieved in 78%. Major complications included stroke (3%), cranial nerve deficit (3%), acute hematoma (1%), and cerebrospinal fluid leak (1%). The modified pericranial flap technique used in 18 recent patients resulted in a shorter duration of transient frontalis paresis and forehead hypesthesia with complete functional recovery in all 18.

CONCLUSION

The SO craniotomy is an effective keyhole approach for intra- and extra-axial tumors. Endoscopic assistance may allow additional tumor removal in almost 30% of the cases. The modified pericranial flap appears to accelerate functional recovery, although additional patients and follow-up are required to better assess this technique.

Mapping metabolism of liver tissue using two-photon FLIM

Although fluorescence lifetime imaging microscopy (FLIM) has been extensively applied to study cellular metabolism in the liver, there is neither an established approach to analyze the data, nor have appropriate protocols been developed to maintain the optical metabolic characteristics in the ex vivo liver tissue sample. Here, we show that a tri-exponential decay fitting model for the fluorescence signal from nicotinamide adenine dinucleotide (NAD(P)H) and the use of ex vivo samples allows the most appropriate processing of the FLIM data. Moreover, we determine the medium that maintains the initial metabolic state of hepatocytes (liver cells), most effectively. Our results should be particularly relevant for the interrogation of liver samples, not only in laboratory research, but also in clinical settings in the future.

Prediction of recurrent glioblastoma after laser interstitial thermal therapy: The role of diffusion imaging

Background

Evaluate the utility of diffusion-weighted imaging (DWI) for the assessment of local recurrence of glioblastoma (GBM) on imaging performed 24 h following MRI-guided laser interstitial thermal therapy (LITT). We hypothesize that microscopic peritumoral infiltration correlates with early subtle variations on DWI images and apparent diffusion coefficient (ADC) maps.

Methods

Of 64 patients with GBM treated with LITT, 39 had MRI scans within 24 h after undergoing LITT. Patterns on DWI images and ADC maps 24 h following LITT were correlated with areas of future GBM recurrence identified through coregistration of subsequent MRI examinations. In the areas of suspected recurrence within the periphery of post-LITT lesions, signal intensity values on ADC maps were recorded and compared with the remaining peritumoral ring.

Results

Thirty-nine patients with GBM met the inclusion criteria. For predicting recurrent GBM, areas of decreased DWI signal and increased signal on ADC maps within the expected peritumoral ring of restricted diffusion identified 24 h following LITT showed 86.1% sensitivity, 75.2% specificity, and high correlation (r = 0.53) with future areas of GBM recurrence (P < .01). Areas of future recurrence demonstrated a 37% increase in the ADC value (P < .001), compared with findings in the surrounding treated peritumoral region. A significantly greater area under the receiver operating characteristics curve was determined for ADC values (P < .01).

Conclusions

DWI obtained 24 h following LITT can help predict the location of GBM recurrence months before the development of abnormal enhancement. This may alter future treatment planning, perhaps suggesting areas that may be targeted for additional therapy.

Blood-Brain Barrier, Blood-Brain Tumor Barrier, and Fluorescence-Guided Neurosurgical Oncology: Delivering Optical Labels to Brain Tumors

Recent advances in maximum safe glioma resection have included the introduction of a host of visualization techniques to complement intraoperative white-light imaging of tumors. However, barriers to the effective use of these techniques within the central nervous system remain. In the healthy brain, the blood-brain barrier ensures the stability of the sensitive internal environment of the brain by protecting the active functions of the central nervous system and preventing the invasion of microorganisms and toxins. Brain tumors, however, often cause degradation and dysfunction of this barrier, resulting in a heterogeneous increase in vascular permeability throughout the tumor mass and outside it. Thus, the characteristics of both the blood-brain and blood-brain tumor barriers hinder the vascular delivery of a variety of therapeutic substances to brain tumors. Recent developments in fluorescent visualization of brain tumors offer improvements in the extent of maximal safe resection, but many of these fluorescent agents must reach the tumor via the vasculature. As a result, these fluorescence-guided resection techniques are often limited by the extent of vascular permeability in tumor regions and by the failure to stain the full volume of tumor tissue. In this review, we describe the structure and function of both the blood-brain and blood-brain tumor barriers in the context of the current state of fluorescence-guided imaging of brain tumors. We discuss features of currently used techniques for fluorescence-guided brain tumor resection, with an emphasis on their interactions with the blood-brain and blood-tumor barriers. Finally, we discuss a selection of novel preclinical techniques that have the potential to enhance the delivery of therapeutics to brain tumors in spite of the barrier properties of the brain.

Indocyanine Green-Coated Polycaprolactone Micelles for Fluorescence Imaging of Tumors

Recently, near-infrared (NIR) fluorescent dyes such as indocyanine green (ICG) have received tremendous interest as contrast agents for use in fluorescence-guided, intraoperative cancer resection surgery. However, despite showing great promise, ICG has many shortcomings such as rapid clearance and poor tumor accumulation. To improve the selective accumulation of ICG within tumors, numerous groups have formulated ICG into nanoparticles, but these approaches can suffer from rapid leakage of ICG, use of materials that exhibit poor or incomplete excretion, or complex chemistries that are not easily amenable to scale up for clinical use. Here, we developed a simple one-step method to prepare ICG-based fluorescent micelles that are composed solely of unmodified ICG and polycaprolactone (PCL), two clinically used materials with well-characterized safety profiles. The ICG-PCL micelles are prepared via oil-in-water emulsions, and the resulting micelles exhibit a uniform size, good reproducibility, and high loading efficiency. In vivo fluorescence imaging demonstrated that the ICG-PCL micelles led to a significant improvement in the accumulation and retention of ICG, in four different tumor models, compared with free dye, making them an attractive option for image-guided surgery.

Utility of sodium fluorescein for achieving resection targets in glioblastoma: increased gross- or near-total resections and prolonged survival

OBJECTIVE

It is commonly reported that achieving gross-total resection of contrast-enhancing areas in patients with glioblastoma (GBM) improves overall survival. Efforts to achieve an improved resection have included the use of both imaging and pharmacological adjuvants. The authors sought to investigate the role of sodium fluorescein in improving the rates of gross-total resection of GBM and to assess whether patients undergoing resection with fluorescein have improved survival compared to patients undergoing resection without fluorescein.

METHODS

A retrospective chart review was performed on 57 consecutive patients undergoing 64 surgeries with sodium fluorescein to treat newly diagnosed or recurrent GBMs from May 2014 to June 2017 at a teaching institution. Outcomes were compared to those in patients with GBMs who underwent resection without fluorescein.

RESULTS

Complete or near-total (≥ 98%) resection was achieved in 73% (47/64) of fluorescein cases. Of 42 cases thought not to be amenable to complete resection, 10 procedures (24%) resulted in gross-total resection and 15 (36%) resulted in near-total resection following the use of sodium fluorescein. No patients developed any local or systemic side effects after fluorescein injection. Patients undergoing resection with sodium fluorescein, compared to the non-fluorescein-treated group, had increased rates of gross- or near-total resection (73% vs 53%, respectively; p < 0.05) as well as improved median survival (78 weeks vs 60 weeks, respectively; p < 0.360).

CONCLUSIONS

This study is the largest case series to date demonstrating the beneficial effect of utilizing sodium fluorescein as an adjunct in GBM resection. Sodium fluorescein facilitated resection in cases in which it was employed, including dominant-side resections particularly near speech and motor regions. The cohort of patients in which sodium fluorescein was utilized had statistically significantly increased rates of gross- or near-total resection. Additionally, the fluorescein group demonstrated prolonged median survival, although this was not statistically significant. This work demonstrates the promise of an affordable and easy-to-implement strategy for improving rates of total resection of contrast-enhancing areas in patients with GBM.

Combined-therapeutic strategies synergistically potentiate glioblastoma multiforme treatment via nanotechnology

Glioblastoma multiforme (GBM) is a highly aggressive and devastating brain tumor characterized by poor prognosis and high rates of recurrence. Numerous therapeutic strategies and delivery systems are developed to prolong the survival time. They exhibit enhanced therapeutic effects in animal models, whereas few of them is applied in clinical trials. Taking into account the drug-resistance and high recurrence of GBM, combined-therapeutic strategies are exploited to maximize therapeutic efficacy. The combined therapies demonstrate superior results than those of single therapies against GBM. The co-therapeutic agents, the timing of therapeutic strategies and the delivery systems greatly affect the overall outcomes. Herein, the current advances in combined therapies for glioblastoma via systemic administration are exhibited in this review. And we will discuss the pros and cons of these combined-therapeutic strategies via nanotechnology, and provide the guidance for developing rational delivery systems to optimize treatments against GBM and other malignancies in central nervous system.

The application of fluorescence techniques in meningioma surgery-a review

Surgical resections of meningiomas, the most common intracranial tumor in adults, can only be curative if radical resection is achieved. Potentially, the extent of resection could be improved, especially in complex and/or high-grade meningiomas by fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA), indocyanine green (ICG), or fluorescein. This review aims to summarize and evaluate these fluorescence-guided meningioma surgery techniques. PubMed and Embase were searched for relevant articles. Additionally, we checked reference lists for further studies. Forty-eight articles were included in the final analysis. 5-ALA fluoresced with varying sensitivity and selectivity in meningiomas and in invaded bone and dura mater. Although ICG was mainly applied for video angiography, one report shows tumor fluorescence 18-28 h post-ICG injection. Lastly, the use of fluorescein could aid in the identification of tumor remnants; however, detection of dural tail is highly questionable. Fluorescence-guided meningioma surgery should be a reliable, highly specific, and sensitive technique. Despite numerous studies reporting the use of fluorescent dyes, currently, there is no evidence that these tools improve the radical resection rate and long-term recurrence-free outcome in meningioma surgery without neurological deficits. Evidence regarding the effectiveness and increased safety of resection after the application of these fluorophores is currently lacking. Future research should focus on the development of a meningioma-targeted, highly sensitive, and specific fluorophore.

Optical Principles of Fluorescence-Guided Brain Tumor Surgery: A Practical Primer for the Neurosurgeon

Fluorescence-guided surgery is a rapidly growing field that has produced some of the most important innovations in surgical oncology in the past decade. These intraoperative imaging technologies provide information distinguishing tumor tissue from normal tissue in real time as the surgery proceeds and without disruption of the workflow. Many of these fluorescent tracers target unique molecular or cellular features of tumors, which offers the opportunity for identifying pathology with high precision to help surgeons achieve their primary objective of a maximal safe resection. As novel fluorophores and fluorescent probes emerge from preclinical development, a practical understanding of the principles of fluorescence remains critical for evaluating the clinical utility of these agents and identifying opportunities for further innovation. In this review, we provide an "in-text glossary" of the fundamental principles of fluorescence with examples of direct applications to fluorescence-guided brain surgery. We offer a detailed discussion of the various advantages and limitations of the most commonly used intraoperative imaging agents, including 5-aminolevulinic acid, indocyanine green, and fluorescein, with a particular focus on the photophysical properties of these specific agents as they provide a framework through which to understand the new agents that are entering clinical trials. To this end, we conclude with a survey of the fluorescent properties of novel agents that are currently undergoing or will soon enter clinical trials for the intraoperative imaging of brain tumors.

Fluorescein Application in Cranial and Spinal Tumors Enhancing at Preoperative MRI and Operated With a Dedicated Filter on the Surgical Microscope: Preliminary Results in 279 Patients Enrolled in the FLUOCERTUM Prospective Study

Objective: Sodium fluorescein, a green, water soluble dye, is used as neurosurgical fluorescent tracer thanks to its property to accumulate in cerebral regions of blood-brain barrier (BBB) disruption. The authors report the preliminary results of a prospective observational study regarding the use of fluorescein-guided technique for the resection of suspected malignant neoplasms of the central nervous system (CNS), contrast enhancing at preoperative magnetic resonance imaging (MRI), using a dedicated filter on the surgical microscope. Methods: In March 2016 the authors started a prospective, observational trial to evaluate intraoperative fluorescence's characteristics of CNS tumors, the percentage of extent of resection thanks to fluorescein aid and side effects related to fluorescein administration. This report is based on a preliminary analysis of the results of first 279 enrolled patients. Fluorescein was intravenously injected after intubation or immediately at the entrance in the operating room for awake procedures; the tumor was removed using a dedicated filter on the surgical microscope in an inside-out fashion until all fluorescent tissue was removed, as considered feasible by the surgeon. Results: The 279 patients finally enrolled in the trial, both firstly diagnosed and recurrent, were categorized according to WHO pathological classification and there were 212 neuroepithelial tumors, 25 brain metastases, 10 cerebral lymphomas, 7 hemangioblastomas, or hemangioendotheliomas and 25 other tumors and conditions. No adverse reaction related to the administration of fluorescein or to the combined use of fluorescein with other fluorophores was registered. Fluorescein accumulated in cerebral regions where the BBB was damaged, representing a significant surgical aid in most of the CNS tumors with contrast enhancement. In cases of complete removal of all fluorescent tissue, as intraoperatively judged by the surgeon, postoperative MRI revealed a gross total resection in 181/198 patients (91.4%). Conclusions: Based on these preliminary results, fluorescein-guided surgery with a dedicated filter on the microscope is a safe and effective technique to improve visualization and resection of different CNS tumors and conditions, based on BBB alteration.

Confocal-Assisted Multispectral Fluorescent Microscopy for Brain Tumor Surgery

Optimal surgical therapy for brain tumors is the combination of complete resection with minimal invasion and damage to the adjacent normal tissue. To achieve this goal, we need advanced imaging techniques on a scale from macro- to microscopic resolution. In the last decade, the development of fluorescence-guided surgery has been the most influential breakthrough, marginally improving outcomes in brain tumor surgery. Multispectral fluorescence microscopy (MFL) is a novel imaging technique that allows the overlapping of a fluorescent image and a white light image in real-time, with delivery of the merged image to the surgeon through the eyepieces of a surgical microscope. MFL permits the detection and characterization of brain tumors using fluorescent molecular markers such as 5-aminolevulinic acid (5-ALA) or indocyanine green (ICG), while simultaneously obtaining high definition white light images to create a pseudo-colored composite image in real-time. Limitations associated with the use of MFL include decreased light imaging intensity and decreased levels of magnification that may compromise maximal tumor resection on a cellular scale. Confocal laser endomicroscopy (CLE) is another novel advanced imaging technique that is based on miniaturization of the microscope imaging head in order to provide the possibility of in vivo microscopy at the cellular level. Clear visualization of the cellular cytoarchitecture can be achieved with 400-fold-1,000-fold magnification. CLE allows on the one hand the intra-operative detection and differentiation of single tumor cells (without the need for intra-operative histologic analysis of biopsy specimens) as well as the definition of borders between tumor and normal tissue at a cellular level, dramatically improving the accuracy of surgical resection. The application and implementation of CLE-assisted surgery in surgical oncology increases not only the number of options for real-time diagnostic imaging, but also the therapeutic options by extending the resection borders of cancer at a cellular level and, more importantly, by protecting the functionality of normal tissue in the adjacent areas of the human brain. In this article, we describe our experience using these new techniques of confocal-assisted fluorescent surgery including analysis on the technology, usability, indications, limitations, and further developments.

Quantitative Third Harmonic Generation Microscopy for Assessment of Glioma in Human Brain Tissue

Distinguishing tumors from normal brain cells is important but challenging in glioma surgery due to the lack of clear interfaces between the two. The ability of label-free third harmonic generation (THG) microscopy in combination with automated image analysis to quantitatively detect glioma infiltration in fresh, unprocessed tissue in real time is assessed. The THG images reveal increased cellularity in grades II-IV glioma samples from 23 patients, as confirmed by subsequent hematoxylin and eosin histology. An automated image quantification workflow is presented for quantitative assessment of the imaged cellularity as a reflection of the degree of glioma invasion. The cellularity is validated in three ways: 1) Quantitative comparison of THG imaging with fluorescence microscopy of nucleus-stained samples demonstrates that THG reflects the true tissue cellularity. 2) Thresholding of THG cellularity differentiates normal brain from glioma infiltration, with 96.6% sensitivity and 95.5% specificity, in nearly perfect (93%) agreement with pathologists. 3) In one patient, a good correlation between THG cellularity and preoperative magnetic resonance and positron emission tomography imaging is demonstrated. In conclusion, quantitative real-time THG microscopy accurately assesses glioma infiltration in ex vivo human brain samples, and therefore holds strong potential for improving the accuracy of surgical resection.

Optimization of high-grade glioma resection using 5-ALA fluorescence-guided surgery: A literature review and practical recommendations from the neuro-oncology club of the French society of neurosurgery

BACKGROUND

When feasible, the surgical resection is the standard first step of the management of high-grade gliomas. 5-ALA fluorescence-guided-surgery (5-ALA-FGS) was developed to ease the intra-operative delineation of tumor borders in order to maximize the extent of resection.

METHODS

A Medline electronic database search was conducted. English language studies from January 1998 until July 2018 were included, following the PRISMA guidelines.

RESULTS

5-ALA can be considered as a specific tool for the detection of tumor remnant but has a weaker sensibility (level 2). 5-ALA-FGS is associated with a significant increase in the rate of gross total resection reaching more than 90% in some series (level 1). Consistently, 5-ALAFGS improves progression-free survival (level 1). However, the gain in overall survival is more debated. The use of 5-ALA-FGS in eloquent areas is feasible but requires simultaneous intraoperative electrophysiologic functional brain monitoring to precisely locate and preserve eloquent areas (level 2). 5-ALA is usable during the first resection of a glioma but also at recurrence (level 2). From a practical standpoint, 5-ALA is orally administered 3 hours before the induction of anesthesia, the recommended dose being 20 mg/kg. Intra-operatively, the procedure is performed as usually with a central debulking and a peripheral dissection during which the surgeon switches from white to blue light. Provided that some precautions are observed, the technique does not expose the patient to particular complications.

CONCLUSION

Although 5-ALA-FGS contributes to improve gliomas management, there are still some limitations. Future methods will be developed to improve the sensibility of 5-ALA-FGS.

Spectral complexity of 5-ALA induced PpIX fluorescence in guided surgery: a clinical study towards the discrimination of healthy tissue and margin boundaries in high and low grade gliomas

Gliomas are diffuse and hard to cure brain tumors. A major reason for their aggressive behavior is their property to infiltrate the brain. The gross appearance of the infiltrative component is comparable to normal brain, constituting an obstacle to extended surgical resection. 5-ALA induced PpIX fluorescence measurements enable gains in sensitivity to detect infiltrated cells, but still lack sensitivity to get accurate discrimination between the tumor margin and healthy tissue. In this fluorescence spectroscopic study, we assume that two states of PpIX contribute to total fluorescence to get better discrimination of healthy tissues against tumor margins. We reveal that fluorescence in low-density margins of high-grade gliomas or in low-grade gliomas is mainly influenced by the second state of PpIX centered at 620 nm. We thus conclude that consideration of the contributions of both states to total fluorescence can help to improve fluorescence-guided resection of gliomas by discriminating healthy tissues from tumor margins.

Dual-modality optical diagnosis for precise in vivo identification of tumors in neurosurgery

In neurosurgery, the precise diagnosis and treatment of tumor diseases are challenging to realize. Current clinical diagnoses lack fast and accurate intraoperative information. Therefore, the development of new methods and techniques to assist neurosurgeons intraoperatively is necessary. Optical diagnosis is a promising method to provide accurate information about biological tissues in a short time. Therefore, in this study, we proposed a dual-modality optical diagnostic method through point-to-face registration fusion in the optical system. We incorporated quantitative autofluorescence spectroscopy and optical coherence tomography (OCT) and evaluated our methods in an animal model.

Methods: A mouse model consisting of 16 nude mice was built by injecting the mouse brains with human glioma cells. Preoperative bioluminescence imaging was used to evaluate the growth states of tumors and locate the tumor sites. Quantitative autofluorescence spectroscopy, which provided local biochemical information with single-point detection, and OCT, which provided relatively global structural information with en face mapping scanning, were combined using the point-to-face registration fusion method to provide precise diagnostic information for identifying the brain tumors. Postoperative pathology was performed to evaluate the sensitivity and specificity of optical diagnosis.

Results: Ex vivo quantitative autofluorescence spectroscopy and OCT imaging were first performed in eight mice to acquire the optimal measuring parameters for tumor staging and identification. We then performed in vivo quantitative autofluorescence spectroscopy and OCT imaging. The results showed that tumor staging could be realized through quantitative autofluorescence spectroscopy, and fusion images could be used to precisely identify tumors. The autofluorescence spectral map, OCT en face map, and fused diagnostic map had average sensitivities of 91.7%, 86.1%, and 95.9% and specificities of 93.2%, 96.0%, and 88.7%, respectively, for tumor identification.

Conclusion: The dual-modality optical point-to-face registration fusion method and system we proposed could provide both biochemical information and structural information. The in vivo experimental results validated that the sensitivity (95.9%) of the fused map was higher than that of either single diagnostic modality (86.1% or 91.7%). Tumor staging was realized through quantitative autofluorescence spectroscopy. The proposed method will be applicable to future intelligent theranostic systems and improve many clinical neurosurgeries.

In vivo demonstration of blood-brain barrier impairment in Moyamoya disease

BACKGROUND

Moyamoya disease (MMD) is a cerebrovascular disorder characterized by fragile vascular system. Previous studies suggested that the blood-brain barrier (BBB) destabilizing cytokine angiopoietin-2 plays a critical role in increasing vascular plasticity and endothelial disintegration in MMD. The aim of this study was to assess cerebrovascular integrity in vivo in patients affected by MMD.

METHODS

We retrospectively analyzed 11 patients that underwent bypass for MMD (MMD group), 11 patients that underwent bypass for atherosclerotic cerebrovascular disease (ACVD-control group I), and 5 patients that underwent clipping for unruptured aneurysms (non-ischemic-control group II). Sodium fluorescein (NaFL) extravasation was evaluated during videoangiography when checking for bypass patency. A grading system (0, +, ++, +++) was used to define the extent of extravasation. Frequency and intensity of leakage was compared among different groups.

RESULTS

NaFL extravasation appeared in 10/11 (91%) patients with MMD and in 8/11 (73%) patients with ACVD during bypass procedures. Extravasation was observed in none of the patients undergoing clipping for unruptured aneurysms. Although both chronic ischemic patient groups showed a comparably high incidence of NaFL extravasation, the MMD group was characterized by a much greater intensity of NaFL extravasation (grade +++ in 82%) than the ACVD group (grade +++ in 27%, p < 0.05).

CONCLUSIONS

We demonstrate blood-brain barrier impairment in MMD patients for the first time in vivo. This may be due to mechanisms intrinsic to the unique pathology of MMD, probably explaining the higher association with hemorrhage and post-operative hyperperfusion.

Diffusion Tensor Imaging with Fluorescein Sodium Staining in the Resection of High-Grade Gliomas in Functional Brain Areas

OBJECTIVE

To evaluate the feasibility and clinical value of magnetic resonance diffusion tensor imaging (DTI) with fluorescein sodium staining (FLS) in the resection of high-grade glioma (HGG) in functional brain areas.

METHODS

Retrospective cohort study design. The data of 95 patients who underwent surgery at the First Affiliated Hospital of Zhengzhou University for HGG in functional brain areas from October 2014 to December 2017 were investigated. In the observation group, 49 patients underwent DTI preoperatively and received FLS for the removal of tumor during the operation. In the control group, 46 patients received the routine method. All patients were subjected to enhanced magnetic resonance imaging to assess the extent of tumor resection within 72 hours after operation. The changes in muscle strength and Karnofsky Performance Status Scale (KPS) scores were evaluated 1 month after surgery.

RESULTS

The extent of resection was significantly higher in the observation group than in the control group (83.7% vs. 45.7%, respectively; P < 0.001). The rate of muscle strength reduction after surgery was remarkably lower in the observation group than in the control group (20.4% vs. 47.8%, respectively; P = 0.005). KPS scores were higher in the observation group than in the control group (73.5% vs. 47.8%, respectively; P = 0.029). In the observation group, the sensitivity of FLS in identifying tumor tissue was 91.7% (44/48), with a specificity of 90.0% (45/50).

CONCLUSIONS

The application of DTI with FLS can facilitate the maximum resection of HGG in functional brain areas with minimum loss of fiber tracts, reduce the disability rate, and improve quality of postoperative life compared with traditional glioma surgery.

The role of 5-aminolevulinic acid in spinal tumor surgery: a review

Purpose

Primary intradural spinal neoplasms account for a small proportion of central nervous system tumors. The primary treatment for these tumors consists of maximal safe resection and preservation of neurologic function. Gross total resection, which is associated with the lowest rate of tumor recurrence and longer progression-free survival for most histologies, can be difficult to achieve. Currently, the use of 5-aminolevulinc acid (5-ALA) which takes advantage of Protoporphyrin IX (PpIX) fluorescence, is a well-established technique for improving resection of malignant cerebral gliomas. This technique is being increasingly applied to other cerebral neoplasms, and multiple studies have attempted to evaluate the utility of 5-ALA-aided resection of spinal neoplasms.

Methods

The authors reviewed the existing literature on the use of 5-ALA and PpIX fluorescence as an aid to resection of primary and secondary spinal neoplasms by searching the PUBMED and EMBASE database for records up to March 2018. Data was abstracted from all studies describing spinal neurosurgical uses in the English language.

Results

In the reviewed studies, the most useful fluorescence was observed in meningiomas, ependymomas, drop metastases from cerebral gliomas, and hemangiopericytomas of the spine, which is consistent with applications in cerebral neoplasms.

Conclusions

The available literature is significantly limited by a lack of standardized methods for measurement and quantification of 5-ALA fluorescence. The results of the reviewed studies should guide future development of rational trial protocols for the use of 5-ALA guided resection in spinal neoplasms.

Electronic supplementary material

The online version of this article (10.1007/s11060-018-03080-0) contains supplementary material, which is available to authorized users.

Optimizing Glioma Detection Using an EGFR-Targeted Fluorescent Affibody

Since many types of cancers overexpress EGFR, this surface receptor has been used as a target for therapy or diagnosis of malignant disease. Uptake kinetics of EGFR-targeted fluorescent Affibody (ABY-029) were studied with a view toward optimizing efficacy of tumor detection in a glioma as a function of both delivered dose and concurrent administration of unlabeled cetuximab (an EGFR antagonist). U251 glioma cells were inoculated in brain of nude rats, and the fluorescence from each brain was analyzed after the administration of ABY-029. Although cetuximab was able to systematically block ABY-029 binding to EGFR in a dose-dependent manner in cell culture, no influence on the tumor-to-normal brain contrast was seen when unlabeled cetuximab was administered prior to ABY-029. Ex vivo imaging of ABY-029 fluorescence showed increasing values of the tumor-to-normal brain ratio with an increasing injected dose. A saturation value was obtained at a dose of 245 μg kg-1 which represents a 10-fold increase over a "microdose" value. According to FDA, the microdose of protein products is considered ≤30 nanomoles due to its difference in molecular weight as compared to synthetic drugs. This observation indicates that glioma detection will be optimal if the ABY-029 dose exceeds the "microdose" value.

Fluorescence-guided surgery with aminolevulinic acid for low-grade gliomas

INTRODUCTION

Fluorescence guided surgery has developed over the last 2 decades as a formidable augmentation strategy to promote maximal safe resection and diagnostic accuracy within gliomas. The majority of the literature evidence supporting this modality utilizes 5-aminolevulinic acid in the setting of high-grade gliomas. The role for fluorescence guided surgery in low-grade gliomas is less well defined.

RESULTS

This review describes the existing literature discussing the utilization of 5-aminolevulinic acid for fluorescence guided surgery in low-grade gliomas, including its pertinence in identification of anaplastic foci and potential role in guiding resection following combination with augmentation strategies for detection.

CONCLUSION

The advance in operative technology and growth of research analyzing 5-aminolevulinic acid will continue to enhance the role of fluorescence guided surgery within the standard of surgical management for low-grade gliomas.