Emerging operative strategies in neurosurgical oncology

The Landscape of Neurosurgical Oncology Adjunct Usage in Africa: A Scoping Review

BACKGROUND

Intraoperative neurosurgical adjuncts improve extent of resection whilst mitigating patient morbidity. The delivery of neurosurgical care via these adjuncts is the norm in high-income countries, but there is yet to be a study highlighting the usage of neurosurgical oncology adjuncts in Africa. This paper aims to provide awareness of the use of these adjuncts in Africa, reasons for limited procurement, and possible solutions to the problem.

METHODS

This scoping review was conducted in accordance with Preferred Reporting Items for Systematic Review and Meta-Analysis Extension for Scoping Reviews guidelines. Semantic derivatives of neurosurgical oncology, adjuncts, and Africa were applied to medical databases. Studies in Africa with outcomes relating to adjunct usage, morbidity, mortality, and quality of life were selected. Book chapters and reviews were excluded.

RESULTS

Thirteen studies with 287 patients (0.5 to 74 years) were included in the final analysis. Most studies were cohort observational (46.2%) and originated from South Africa (46.2%). Meningioma was the most prevalent tumor histology (39.4%), and neuronavigation was the most readily used adjunct for surgical resection (30.8%). Using adjuncts, gross total resection was achieved in close to half the patient cohort (49.8%). Limited technology, lack of experience, cost of equipment, and inconsistency in power supply were noted as factors contributing to lack of adjunct usage.

CONCLUSIONS

Neurosurgical adjuncts provide significant benefits in neurosurgical oncology. There is limited utilization of intraoperative adjuncts in most of Africa owing to limited resources and experienced professionals. Bilateral partnerships with a focus on donation and education will foster safe and sustainable adjunct incorporation in Africa.

Partially linear Bayesian modeling of longitudinal rank and time-to-event data using accelerated failure time model with application to brain tumor data

Joint modeling of longitudinal rank and time-to-event data with random effects model using a Bayesian approach is presented. Accelerated failure time (AFT) models can be used for the analysis of time-to-event data to estimate the effects of covariates on acceleration/deceleration of the survival time. The parametric AFT models require determining the event time distribution. So, we suppose that the time variable is modeled with Weibull AFT distribution. In many real-life applications, it is difficult to determine the appropriate distribution. To avoid this restriction, several semiparametric AFT models were proposed, containing spline-based model. So, we propose a flexible extension of the accelerated failure time model. Furthermore, the usual joint linear model, a joint partially linear model, is also considered containing the nonlinear effect of time on the longitudinal rank responses and nonlinear and time-dependent effects of covariates on the hazard. Also, a Bayesian approach that yields Bayesian estimates of the model's parameters is used. Some simulation studies are conducted to estimate parameters of the considered models. The model is applied to a real brain tumor patient's data set that underwent surgery. The results of analyzing data are presented to represent the method.

Standard clinical approaches and emerging modalities for glioblastoma imaging

Glioblastoma (GBM) is the most common primary adult intracranial malignancy and carries a dismal prognosis despite an aggressive multimodal treatment regimen that consists of surgical resection, radiation, and adjuvant chemotherapy. Radiographic evaluation, largely informed by magnetic resonance imaging (MRI), is a critical component of initial diagnosis, surgical planning, and post-treatment monitoring. However, conventional MRI does not provide information regarding tumor microvasculature, necrosis, or neoangiogenesis. In addition, traditional MRI imaging can be further confounded by treatment-related effects such as pseudoprogression, radiation necrosis, and/or pseudoresponse(s) that preclude clinicians from making fully informed decisions when structuring a therapeutic approach. A myriad of novel imaging modalities have been developed to address these deficits. Herein, we provide a clinically oriented review of standard techniques for imaging GBM and highlight emerging technologies utilized in disease characterization and therapeutic development.

Imaging and treatment of brain tumors through molecular targeting: Recent clinical advances

Molecular imaging techniques have rapidly progressed over recent decades providing unprecedented in vivo characterization of metabolic pathways and molecular biomarkers. Many of these new techniques have been successfully applied in the field of neuro-oncological imaging to probe tumor biology. Targeting specific signaling or metabolic pathways could help to address several unmet clinical needs that hamper the management of patients with brain tumors. This review aims to provide an overview of the recent advances in brain tumor imaging using molecular targeting with positron emission tomography and magnetic resonance imaging, as well as the role in patient management and possible therapeutic implications.

5-ALA fluorescence-guided surgery in pediatric brain tumors-a systematic review

BACKGROUND

5-Aminolevulinic acid (5-ALA)-guided resection of gliomas in adults enables better differentiation between tumor and normal brain tissue, allowing a higher degree of resection, and improves patient outcomes. In recent years, several reports have emerged regarding the use of 5-ALA in other brain tumor entities, including pediatric brains tumors. Since gross total resection (GTR) of many brain tumors in children is crucial and the role of 5-ALA-guided resection of these tumors is not clear, we sought to perform a comprehensive literature review on this topic.

METHODS

A systematic literature review of EMBASE and MEDLINE/PubMed databases revealed 19 eligible publications encompassing 175 5-ALA-guided operations on pediatric brain tumors. To prevent bias, publications were revised independently by two authors.

RESULTS

We found that 5-ALA-guided resection enabled the surgeons to identify the tumor more easily and was considered helpful mainly in cases of glioblastoma (GBM, 21/27, 78%), anaplastic ependymoma WHO grade III (10/14, 71%), and anaplastic astrocytoma (4/6, 67%). In contrast, cases of pilocytic astrocytomas (PAs) and medulloblastomas 5-ALA-guided surgery did not show consistent fluorescent signals and 5-ALA was considered helpful only in 12% and 22% of cases, respectively. Accumulation of fluorescent porphyrins seems to depend on WHO tumor grading. One important finding is that when 5-ALA-guided resections were considered helpful, the degree of resection was higher than is cases where it was not helpful. The rate of adverse events related to 5-ALA was negligible, especially new postoperative sequelae.

CONCLUSION

5-ALA could play a role in resection of pediatric brain tumors. However, further prospective clinical trials are needed.

In-Vitro Use of 5-ALA for Photodynamic Therapy in Pediatric Brain Tumors

BACKGROUND

Light irradiation (635 nm) of cells containing protoporphyrin IX (PPIX) after 5- aminolevulinic acid (5-ALA) pretreatment causes cell death via different pathways including apoptosis and necrosis, as previously demonstrated for malignant glioma cells.

OBJECTIVE

To elucidate whether various malignant pediatric brain tumors, which have been shown to accumulate PPIX, would also be susceptible to photodynamic therapy (PDT).

METHODS

Medulloblastoma (DAOY, UW228), pNET (PFSK-1), and rhabdoid tumor (BT16) cell lines were incubated with 5-ALA in variable concentrations for 4 h. Consequently, cells were irradiated by 635 nm diode laser light. After 12 h, cell viability was measured by WST-1 testing and these results were compared to control cells incubated with 5-ALA without irradiation or irradiation only without prior incubation with 5-ALA.

RESULTS

We demonstrated significant cell death in malignant pediatric tumor cells after incubation with 5-ALA and laser irradiation in comparison to control groups. In all cell lines, we noticed significant cell death above a 5-ALA concentration of 50 μg/ml (P < .05). Neither 5-ALA incubation alone nor irradiation alone caused cell death. DAOY and PFSK cell lines were more susceptible than UW228 and BT16 cells.

CONCLUSION

We conclude that PDT causes cell death with higher PPIX concentrations after exposure to 5-ALA in vitro in accordance to similar studies with glioma cells. This indicates that PDT might be feasible for eliminating brain tumor cells in malignant pediatric brain tumors. Additionally, we noticed a dependency between fluorescence intensity and death rates.

Semi-Automated Volumetric and Morphological Assessment of Glioblastoma Resection with Fluorescence-Guided Surgery

PURPOSE

Glioblastoma (GBM) neurosurgical resection relies on contrast-enhanced MRI-based neuronavigation. However, it is well-known that infiltrating tumor extends beyond contrast enhancement. Fluorescence-guided surgery (FGS) using 5-aminolevulinic acid (5-ALA) was evaluated to improve extent of resection (EOR) of GBMs. Preoperative morphological tumor metrics were also assessed.

PROCEDURES

Thirty patients from a phase II trial evaluating 5-ALA FGS in newly diagnosed GBM were assessed. Tumors were segmented preoperatively to assess morphological features as well as postoperatively to evaluate EOR and residual tumor volume (RTV).

RESULTS

Median EOR and RTV were 94.3 % and 0.821 cm(3), respectively. Preoperative surface area to volume ratio and RTV were significantly associated with overall survival, even when controlling for the known survival confounders.

CONCLUSIONS

This study supports claims that 5-ALA FGS is helpful at decreasing tumor burden and prolonging survival in GBM. Moreover, morphological indices are shown to impact both resection and patient survival.

Contribution of combined intraoperative electrophysiological investigation with 3-T intraoperative MRI for awake cerebral glioma surgery: comprehensive review of the clinical implications and radiological outcomes

OBJECTIVE

This study aimed to assess the clinical efficiency of combined awake craniotomy with 3-T intraoperative MRI (iMRI)-guided resection of gliomas adjacent to eloquent cortex performed at a single center. It also sought to explore the contribution of iMRI to surgeons' learning process of maximal safe resection of gliomas.

METHODS

All patients who underwent an awake craniotomy and iMRI for resection of eloquent area glioma during the 53 months between January 2011 and June 2015 were included. The cases were analyzed for short- and long-term neurological outcome, progression-free survival (PFS), overall survival (OS), and extent of resection (EOR). The learning curve was assessed after dividing the cohort into Group A (first 27 months) and Group B (last 26 months). Statistical analyses included univariate logistic regression analysis on clinical and radiological variables. Kaplan-Meier and Cox regression models were used for further analysis of OS and PFS. A p value < 0.05 was considered statistically significant.

RESULTS

One hundred six patients were included in the study. Over an average follow-up period of 24.8 months, short- and long-term worsening of the neurological function was noted in 48 (46.2%) and 9 (8.7%) cases, respectively. The median and mean EOR were 100% and 92%, respectively, and complete radiographic resection was achieved in 64 (60.4%) patients. The rate of gross-total resection (GTR) in the patients with low-grade glioma (89.06% ± 19.6%) was significantly lower than that in patients with high-grade glioma (96.4% ± 9.1%) (p = 0.026). Thirty (28.3%) patients underwent further resection after initial iMRI scanning, with a 10.1% increase of the mean EOR. Multivariate Cox proportional hazards modeling demonstrated that the final EOR was a significant predictor of PFS (HR 0.225, 95% CI 0.070-0.723, p = 0.012). For patients with high-grade glioma, the GTR (p = 0.033), the presence of short-term motor deficit (p = 0.027), and the WHO grade (p = 0.005) were independent prognostic factors of OS. Performing further resection after the iMRI (p = 0.083) and achieving GTR (p = 0.05) demonstrated a PFS benefit trend for the patients affected by a low-grade glioma. Over time, the rate of performing further resection after an iMRI decreased by 26.1% (p = 0.005). A nonsignificant decrease in the rate of short-term (p = 0.101) and long-term (p = 0.132) neurological deficits was equally noted.

CONCLUSIONS

Combined awake craniotomy and iMRI is a safe and efficient technique allowing maximal safe resection of eloquent area gliomas with possible subsequent OS and PFS benefits. Although there is a learning curve for applying this technique, it can also improve the surgeon's ability in eloquent glioma surgery.

Preoperative language mapping by repetitive navigated transcranial magnetic stimulation and diffusion tensor imaging fiber tracking and their comparison to intraoperative stimulation

INTRODUCTION

Repetitive navigated transcranial magnetic stimulation (rTMS) can be used for preoperative language mapping, but it still suffers from comparatively high sensitivity and low specificity when compared to direct cortical stimulation (DCS). Therefore, this study evaluates whether the additional consideration of rTMS-based diffusion tensor imaging fiber tracking (DTI FT) for identifying language-positive brain regions improves specificity when compared to DCS.

METHODS

We performed rTMS, rTMS-based DTI FT, and DCS during awake surgery combined with object naming in 20 patients suffering from left-sided perisylvian brain lesions. For rTMS, different error rate thresholds (ERTs) and error types were considered, and DTI FT was conducted with individualized fractional anisotropy thresholds (FATs). Then, receiver operating characteristics (ROC) for rTMS vs. DCS, rTMS-based DTI FT vs. DCS, and rTMS spots confirmed by rTMS-based DTI FT vs. DCS were calculated.

RESULTS

In general, rTMS vs. DCS was in good accordance with previous literature (sensitivity/specificity: 92.7/13.3 % for all naming errors without ERT). In addition, rTMS-based DTI FT vs. DCS led to balanced results when tracking was based on all errors as well (sensitivity/specificity: 62.8/64.3 % for 100 % FAT). However, rTMS combined with rTMS-based DTI FT vs. DCS did not lead to any improvement in specificity when compared to rTMS vs. DCS alone.

CONCLUSION

The additional use of rTMS-based DTI FT to rTMS did not improve the identification of DCS-positive language areas during awake surgery. Yet, concerning rTMS-based DTI FT, this new technique must be validated itself by intraoperative subcortical stimulation.

Luminescence-based Imaging Approaches in the Field of Interventional Molecular Imaging

Luminescence imaging-based guidance technologies are increasingly gaining interest within surgical and radiologic disciplines. Their promise to help visualize molecular features of disease in real time and with microscopic detail is considered desirable. Integrating luminescence imaging with three-dimensional radiologic- and/or nuclear medicine-based preinterventional imaging may overcome limitations such as the limited tissue penetration of luminescence signals. At the same time, the beneficial features of luminescence imaging may be used to complement the routinely used radiologic- and nuclear medicine-based modalities. To fully exploit this integrated concept, and to relate the largely experimental luminesce-based guidance approaches into perspective with routine imaging approaches, it is essential to understand the advantages and limitations of this relatively new modality. By providing an overview of the available luminescence technologies and the various clinically evaluated exogenous luminescent tracers (fluorescent, hybrid, and theranostic tracers), this review attempts to place luminescence-based interventional molecular imaging technologies into perspective to the available radiologic- and/or nuclear medicine-based imaging technologies. At the same time, the transition from anatomic to physiologic and even molecular interventional luminescence imaging is illustrated.

"Extremely minimally invasive": recent advances in nanotechnology research and future applications in neurosurgery

The term "nanotechnology" refers to the development of materials and devices that have been designed with specific properties at the nanometer scale (10(-9) m), usually being less than 100 nm in size. Recent advances in nanotechnology have promised to enable visualization and intervention at the subcellular level, and its incorporation to future medical therapeutics is expected to bring new avenues for molecular imaging, targeted drug delivery, and personalized interventions. Although the central nervous system presents unique challenges to the implementation of new therapeutic strategies involving nanotechnology (such as the heterogeneous molecular environment of different CNS regions, the existence of multiple processing centers with different cytoarchitecture, and the presence of the blood-brain barrier), numerous studies have demonstrated that the incorporation of nanotechnology resources into the armamentarium of neurosurgery may lead to breakthrough advances in the near future. In this article, the authors present a critical review on the current 'state-of-the-art' of basic research in nanotechnology with special attention to those issues which present the greatest potential to generate major therapeutic progresses in the neurosurgical field, including nanoelectromechanical systems, nano-scaffolds for neural regeneration, sutureless anastomosis, molecular imaging, targeted drug delivery, and theranostic strategies.

Neurosurgical oncology: advances in operative technologies and adjuncts

Modern glioma surgery has evolved around the central tenet of safely maximizing resection. Recent surgical adjuncts have focused on increasing the maximum extent of resection while minimizing risk to functional brain. Technologies such as cortical and subcortical stimulation mapping, intraoperative magnetic resonance imaging, functional neuronavigation, navigable intraoperative ultrasound, neuroendoscopy, and fluorescence-guided resection have been developed to augment the identification of tumor while preserving brain anatomy and function. However, whether these technologies offer additional long-term benefits to glioma patients remains to be determined. Here we review advances over the past decade in operative technologies that have offered the most promising benefits for glioblastoma patients.

Kinetics of porphyrin fluorescence accumulation in pediatric brain tumor cells incubated in 5-aminolevulinic acid

BACKGROUND

Fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) enables more complete resections of tumors in adults. 5-ALA elicits accumulation of fluorescent porphyrins in various cancerous tissues, which can be visualized using a modified neurosurgical microscope with blue light. Although this technique is well established in adults, it has not been investigated systematically in pediatric brain tumors. Specifically, it is unknown how quickly, how long, and to what extent various pediatric tumors accumulate fluorescence. The purpose of this study was to determine utility and time course of 5-ALA-induced fluorescence in typical pediatric brain tumors in vitro.

METHODS

Cell cultures of medulloblastoma [DAOY and UW228], cPNET [PFSK] atypical teratoid rhabdoid tumor [BT16] and ependymoma [RES196] were incubated with 5-ALA for either 60 minutes or continuously. Porphyrin fluorescence intensities were determined using a fluorescence-activated cell sorter (FACS) after 1, 3, 6, 9, 12 and 24 hours. C6 and U87 cells served as controls.

RESULTS

All pediatric brain tumor cell lines displayed fluorescence compared to their respective controls without 5-ALA (p < 0.05). Sixty minutes of incubation resulted in peaks between 3 and 6 hours, whereas continuous incubation resulted in peaks at 12 hours or beyond. 60 minute incubation peak levels were between 52 and 91 % of maxima achieved with continuous incubation. Accumulation and clearance varied between cell types.

CONCLUSIONS

We demonstrate that 5-ALA exposure of cell lines derived from typical pediatric central nervous system (CNS) tumors induces accumulation of fluorescent porphyrins. Differences in uptake and clearance indicate that different application modes may be necessary for fluorescence-guided resection, depending on tumor type.

Malignant gliomas: current perspectives in diagnosis, treatment, and early response assessment using advanced quantitative imaging methods

Malignant gliomas consist of glioblastomas, anaplastic astrocytomas, anaplastic oligodendrogliomas and anaplastic oligoastrocytomas, and some less common tumors such as anaplastic ependymomas and anaplastic gangliogliomas. Malignant gliomas have high morbidity and mortality. Even with optimal treatment, median survival is only 12–15 months for glioblastomas and 2–5 years for anaplastic gliomas. However, recent advances in imaging and quantitative analysis of image data have led to earlier diagnosis of tumors and tumor response to therapy, providing oncologists with a greater time window for therapy management. In addition, improved understanding of tumor biology, genetics, and resistance mechanisms has enhanced surgical techniques, chemotherapy methods, and radiotherapy administration. After proper diagnosis and institution of appropriate therapy, there is now a vital need for quantitative methods that can sensitively detect malignant glioma response to therapy at early follow-up times, when changes in management of nonresponders can have its greatest effect. Currently, response is largely evaluated by measuring magnetic resonance contrast and size change, but this approach does not take into account the key biologic steps that precede tumor size reduction. Molecular imaging is ideally suited to measuring early response by quantifying cellular metabolism, proliferation, and apoptosis, activities altered early in treatment. We expect that successful integration of quantitative imaging biomarker assessment into the early phase of clinical trials could provide a novel approach for testing new therapies, and importantly, for facilitating patient management, sparing patients from weeks or months of toxicity and ineffective treatment. This review will present an overview of epidemiology, molecular pathogenesis and current advances in diagnoses, and management of malignant gliomas.

Use of fluorescence to guide resection or biopsy of primary brain tumors and brain metastases

Object

The accurate discrimination between tumor and normal tissue is crucial for determining how much to resect and therefore for the clinical outcome of patients with brain tumors. In recent years, guidance with 5-aminolevulinic acid (5-ALA)–induced intraoperative fluorescence has proven to be a useful surgical adjunct for gross-total resection of high-grade gliomas. The clinical utility of 5-ALA in resection of brain tumors other than glioblastomas has not yet been established. The authors assessed the frequency of positive 5-ALA fluorescence in a cohort of patients with primary brain tumors and metastases.

Methods

The authors conducted a single-center retrospective analysis of 531 patients with intracranial tumors treated by 5-ALA–guided resection or biopsy. They analyzed patient characteristics, preoperative and postoperative liver function test results, intraoperative tumor fluorescence, and histological data. They also screened discharge summaries for clinical adverse effects resulting from the administration of 5-ALA. Intraoperative qualitative 5-ALA fluorescence (none, mild, moderate, and strong) was documented by the surgeon and dichotomized into negative and positive fluorescence.

Results

A total of 458 cases qualified for final analysis. The highest percentage of 5-ALA–positive fluorescence in open resection was found in glioblastomas (96%, n = 99/103). Among other tumors, 5-ALA–positive fluorescence was detected in 88% (n = 21/32) of anaplastic gliomas (WHO Grade III), 40% (n = 8/19) of low-grade gliomas (WHO Grade II), no (n = 0/3) WHO Grade I gliomas, and 77% (n = 85/110) of meningiomas. Among metastases, the highest percentage of 5-ALA–positive fluorescence was detected in adenocarcinomas (48%, n = 13/27). Low rates or absence of positive fluorescence was found among pituitary adenomas (8%, n = 1/12) and schwannomas (0%, n = 0/7). Biopsies of high-grade primary brain tumors showed positive rates of fluorescence similar to those recorded for open resection. No clinical adverse effects associated with use of 5-ALA were observed. Only 1 patient had clinically silent transient elevation of liver enzymes.

Conclusions

Study findings suggest that the administration of 5-ALA as a surgical adjunct for resection and biopsy of primary brain tumors and brain metastases is safe. In light of the high rate of positive fluorescence in high-grade gliomas other than glioblastomas, meningiomas, and a variety of metastatic cancers, 5-ALA seems to be a promising tool for enhancing intraoperative identification of neoplastic tissue and optimizing the extent of resection.

Vestibular schwannoma surgical treatment

Neurosurgical intervention remains the main step in the effective management of vestibular schwannomas. Extensive studies on vestibular schwannoma treatment have placed emphasis on preserving quality of life and neurological functions, particularly of the facial and vestibulocochlear nerves. Facial nerve preservation and hearing preservation have been achieved by significant advances in skull base microsurgical techniques and intraoperative neuromonitoring. Diffusion tensor imaging is a powerful and accurate method for preoperatively identifying the facial nerve in relation to vestibular schwannomas. Endoscopy offers excellent illumination of the anatomical structures and provides panoramic vision inside the surgical area. In this report, we focused on facial nerve and vestibulocochlear nerve preservation and analyzed the major techniques used for identifying the nerve-tumor relationship.