Neurosurgical management of adult diffuse low grade gliomas in Canada: a multi-center survey

Current Trends in Neurosurgical Management of Adult Diffuse Low-Grade Gliomas in Canada

There is considerable variability in the management of diffuse low-grade gliomas (LGGs). To characterize treatment paradigms, a survey of Canadian neurosurgeons was performed with forty neurosurgeons responding. Their responses show that the management of patients with LGGs has evolved in the past decade and findings from the RTOG9802 trial have been integrated into the practice of Canadian neurosurgeons. Most respondents stated that the patient selection and treatment strategy advocated by the RTOG9802 trial needs further evaluation. Overall, there is a trend toward more aggressive surgical resections, and future investigations will have to more accurately stratify patient risk profiles.

Augmented and virtual reality usage in awake craniotomy: a systematic review

Augmented and virtual reality (AR, VR) are becoming promising tools in neurosurgery. AR and VR can reduce challenges associated with conventional approaches via the simulation and mimicry of specific environments of choice for surgeons. Awake craniotomy (AC) enables the resection of lesions from eloquent brain areas while monitoring higher cortical and subcortical functions. Evidence suggests that both surgeons and patients benefit from the various applications of AR and VR in AC. This paper investigates the application of AR and VR in AC and assesses its prospective utility in neurosurgery. A systematic review of the literature was performed using PubMed, Scopus, and Web of Science databases in accordance with the PRISMA guidelines. Our search results yielded 220 articles. A total of six articles consisting of 118 patients have been included in this review. VR was used in four papers, and the other two used AR. Tumour was the most common pathology in 108 patients, followed by vascular lesions in eight patients. VR was used for intraoperative mapping of language, vision, and social cognition, while AR was incorporated in preoperative training of white matter dissection and intraoperative visualisation and navigation. Overall, patients and surgeons were satisfied with the applications of AR and VR in their cases. AR and VR can be safely incorporated during AC to supplement, augment, or even replace conventional approaches in neurosurgery. Future investigations are required to assess the feasibility of AR and VR in various phases of AC.

Management of Diffuse Low-Grade Glioma: The Renaissance of Robust Evidence

The surgical management of diffuse low-grade gliomas (DLGGs) has undergone a paradigm shift toward striving for maximal safe resection when feasible. While extensive observational data supports this transition, unbiased evidence in the form of high quality randomized-controlled trials (RCTs) is lacking. Furthermore, despite a high volume of molecular, genetic, and imaging data, the field of neuro-oncology lacks personalized care algorithms for individuals with DLGGs based on a robust foundation of evidence. In this manuscript, we (1) discuss the logistical and philosophical challenges hindering the development of surgical RCTs for DLGGs, (2) highlight the potential impact of well-designed international prospective observational registries, (3) discuss ways in which cutting-edge computational techniques can be harnessed to generate maximal insight from high volumes of multi-faceted data, and (4) outline a comprehensive plan of action that will enable a multi-disciplinary approach to future DLGG management, integrating advances in clinical medicine, basic molecular research and large-scale data mining.

Filtration-histogram based magnetic resonance texture analysis (MRTA) for glioma IDH and 1p19q genotyping

BACKGROUND

To determine if filtration-histogram based texture analysis (MRTA) of clinical MR imaging can non-invasively identify molecular subtypes of untreated gliomas.

METHODS

Post Gadolinium T1-weighted (T1+Gad) images, T2-weighted (T2) images and apparent diffusion coefficient (ADC) maps of 97 gliomas (54 = WHO II, 20 = WHO III, 23 = WHO IV) between 2010 and 2016 were studied. Whole-tumor segmentations were performed on a proprietary texture analysis research platform (TexRAD, Cambridge, UK) using the software's freehand drawing tool. MRTA commences with a filtration step, followed by quantification of texture using histogram texture parameters. Results were correlated using non-parametric statistics with a logistic regression model generated.

RESULTS

T1+Gad performed best for IDH typing of glioblastoma (sensitivity 91.9%, specificity 100%, AUC 0.945) and ADC for non-Gadolinium-enhancing gliomas (sensitivity 85.7%, specificity 78.4%, AUC 0.877). T2 was moderately precise (sensitivity 83.1%, specificity 78.9%, AUC 0.821). Excellent results for IDH typing were achieved from a combination of the three sequences (sensitivity 90.5%, specificity 94.5%, AUC = 0.98). For discriminating 1p19q genotypes, ADC produced the best results using unfiltered textures (sensitivity 80.6%, specificity 89.3%, AUC 0.811).

CONCLUSION

Preoperative glioma genotyping with MRTA appears valuable with potential for clinical translation. The optimal choice of texture parameters is influenced by sequence choice, tumour morphology and segmentation method.

Tumour volume reduction following PET guided intensity modulated radiation therapy and temozolomide in IDH mutated anaplastic glioma

The role of maximal surgical debulking in isocitrate dehydrogenase (IDH) mutated anaplastic glioma prior to adjuvant radiation therapy remains uncertain. This study assessed the reduction in tumour volume following intensity modulated radiation therapy (IMRT) and temozolomide in this favourable and more responsive tumour pathology. 56 patients were managed from 2011 to 2014 and 53 had residual disease. To assess radiological response, tumour volumes were created on representative T1/T2Flair MRI sequences using identical slice-levels in three planes for pre-IMRT, month + 3 and month + 12 post-IMRT scans. Change in volumes was assessed between time periods. Progression-free survival (PFS) was calculated from start of radiotherapy. Median follow-up for survivors is 48.2 months. Pathology was anaplastic oligodendroglioma (AOD) and anaplastic astrocytoma IDH-mutated (AAmut) in 32 and 21 patients respectively. 93% received sequential chemotherapy. The median residual disease on T1 and T2Flair imaging was 9.7 cm³ and 20.6 cm³. 17 patients relapsed for projected 5 year PFS of 74.9%; with 8 isolated relapses within initial surgical site. On MRI at month + 3, the median volume for T1 and T2Flair reduced by 69.4% and 67.3% respectively; which further decreased to 82.4% and 81.3% at month + 12. By month + 12, 69.2% and 62.2% of patients had >75% volume reduction. Patients with AOD had superior reduction at month + 3 compared with AAmut (p = 0.02); but equivalent reduction at month + 12 (p = 0.14). Thus, in patients with anaplastic glioma harbouring an IDH mutation, where an attempt at near-total resection may be associated with unacceptable morbidity, this data suggests that the radiation therapy may provide effective cytoreduction of residual disease.

A trend towards a more intense adjuvant treatment of low-grade-gliomas in tertiary centers in Germany after RTOG 9802 - results from a multi-center survey

BACKGROUND

The treatment recommendations for Low-grade Gliomas (LGG) underwent profound changes due to results from RTOG 9802 published in April 2016. This work aims to investigate whether the results from the trial were already incorporated into the treatment recommendations at German oncology centers before an update of the official guidelines.

METHODS

An online based questionnaire with questions covering all aspects of adjuvant treatments of LGGs was generated, including three cases with distinct clinical situations. We contacted all members of the neuro-oncologic working group (NOA) of the German Cancer Society (DKG) as well as all German-speaking members of the European Low-Grade Glioma Network via E-mail.

RESULTS

We collected 38 responses. All responders were at least specialists; they predominantly worked at tertiary hospitals with a high volume of LGGs treated annually (75% with more than 10 cases per year). All responders stated to consent treatment recommendation for LGGs within interdisciplinary oncologic boards. The treatment recommendations for LGGs changed profoundly between 2015 and 12/2016. There is a trend towards PCV-based multimodal treatments, especially for oligodendroglial LGGs, as well as a trend away from watchful-waiting-policies for astrocytic LGGs.

CONCLUSION

Neurooncologists do adapt results from clinical trials quickly. None the less, there is still an immense heterogeneity within the treatment recommendations, predominantly for astrocytic LGGs. Well planned clinical trials and concise treatment recommendations are warranted; additionally, individual counseling of patients is essential.

Apparent diffusion coefficient for molecular subtyping of non-gadolinium-enhancing WHO grade II/III glioma: volumetric segmentation versus two-dimensional region of interest analysis

Objectives

To investigate if quantitative apparent diffusion coefficient (ADC) measurements can predict genetic subtypes of non-gadolinium-enhancing gliomas, comparing whole tumour against single slice analysis.

Methods

Volumetric T2-derived masks of 44 gliomas were co-registered to ADC maps with ADC mean (ADC_mean) calculated. For the slice analysis, two observers placed regions of interest in the largest tumour cross-section. The ratio (ADC_ratio) between ADC_mean in the tumour and normal appearing white matter was calculated for both methods.

Results

Isocitrate dehydrogenase (IDH) wild-type gliomas showed the lowest ADC values throughout (p < 0.001). ADC_mean in the IDH-mutant 1p19q intact group was significantly higher than in the IDH-mutant 1p19q co-deleted group (p < 0.01). A volumetric ADC_mean threshold of 1201 × 10⁻⁶ mm²/s identified IDH wild-type with a sensitivity of 83% and a specificity of 86%; a volumetric ADC_ratio cut-off value of 1.65 provided a sensitivity of 80% and a specificity of 92% (area under the curve (AUC) 0.9–0.94). A slice ADC_ratio threshold for observer 1 (observer 2) of 1.76 (1.83) provided a sensitivity of 80% (86%), specificity of 91% (100%) and AUC of 0.95 (0.96). The intraclass correlation coefficient was excellent (0.98).

Conclusions

ADC measurements can support the distinction of glioma subtypes. Volumetric and two-dimensional measurements yielded similar results in this study.

Key Points

• Diffusion-weighted MRI aids the identification of non-gadolinium-enhancing malignant gliomas

• ADC measurements may permit non-gadolinium-enhancing glioma molecular subtyping

• IDH wild-type gliomas have lower ADC values than IDH-mutant tumours

• Single cross-section and volumetric ADC measurements yielded comparable results in this study

Canadian Neurosurgery Educators' Views on Stereotactic Radiosurgery in Residency Training

OBJECTIVE

Despite the increasing prominence of stereotactic radiosurgery (SRS) in treating intracranial and spinal pathologies, there is currently a dearth of exposure to this modality in the neurosurgical residency. To address this gap, the aim of this study is to assess neurosurgery educators' views regarding the current state of SRS exposure, and to identify potential approaches to improve residency education in this domain.

METHODS

Qualitative thematic analysis and constructivist grounded theory methodology were employed. Semistructured telephone-based interviews were conducted with current or past residency program directors, as well as current departmental chairs across neurosurgical departments in Canada. Interviews were transcribed and subjected to thematic analysis using open and axial coding.

RESULTS

Of the 34 eligible participants, the overall response rate was 41.1% (14/34), with a 35.3% participation rate (12/34). Participants represented 9 of the 12 Canadian institutions surveyed. The majority of participants were current program directors (n = 8), followed by past program directors (n = 2), and departmental chairs (n = 2). Most respondents 75% (9/12) view an increasing role for SRS in neurosurgery. Unanimously, respondents endorse greater exposure to SRS during residency through formal residency rotations and engagement in interdisciplinary tumor boards to facilitate involvement in clinical decision-making.

CONCLUSIONS

This is the first study to systematically collate neurosurgery educators' views on SRS in residency in Canada and demonstrates recognition of the discordance between SRS in practice and residency training. Neurosurgery educators broadly endorse increased exposure to this modality. Future work is needed to delineate the requirements necessary to achieve adequate competency in SRS.

The Role of ATRX in Glioma Biology

The current World Health Organization classification of CNS tumors has made a tremendous leap from past editions by incorporating molecular criteria in addition to the pre-existing histological parameters. The revised version has had a particular impact on the classification of diffuse low-grade gliomas and their high-grade variants. The ATRX status is one of the critical markers that define the molecular classification of gliomas. In this review, we will first provide an overview of the role of ATRX in regular cell biology. Furthermore, the role of ATRX in tumorigenesis, specifically gliomas, is comprehensively elucidated. The possible correlation of ATRX status with other genetic/epigenetic modifications is also presented. We conclude by discussing some of the challenges associated with incorporating ATRX status assessment into routine clinical practice while also exploring opportunities for future diagnostics/therapeutics in gliomas based on ATRX status.

Emotional concerns and coping strategies in Low Grade Glioma patients and reliability of their caregivers in reporting these concerns: Findings from a cross-sectional study

PURPOSE

To explore the emotional concerns and coping strategies of patients with Low Grade Glioma (LGG) and whether or not their caregivers are reliable in reporting these concerns as surrogate informants.

METHODS

An explorative cross-sectional study. Patients who had undergone a neurosurgical procedure at least one year before this study for LGG and who were capable of participating in a face-to-face interview were included. Each patient nominated a reference caregiver. Both the patient and the caregiver were interviewed independently, using the Beck Depression Inventory Scale, the State - Trait Anxiety Inventory, and the Jalowiec Coping Scale.

MAIN RESULTS

Forty-six patients and 46 caregivers were included. The average scores of the Beck scale were homogeneous between patients and caregivers (7.76 [CI 95% 5.76-9.75] vs. 6.23 [CI 95% 4.57-7.90]; p = 0.102). Patients reported significantly greater state and trait anxiety (44.26 [CI 95% 40.21-48.31] and 37.95 [CI 95% 34.97-40.94]), respectively compared to their caregivers (40.28 [CI 95% 36.64-43.91] and 35.17 [CI 95% 32.16-38.18]). The coping strategies enacted were homogeneous between patients and caregivers (82.78 [CI 95% 77.21-88.35] vs (80.93 [CI 95% 76.32-85.55]; p = 0.102) while the kind of strategies adopted were significantly diverse.

CONCLUSIONS

Patients suffer from depression and greater state anxiety as compared to trait anxiety; moreover, they enact less than half of the available coping strategies. Caregivers may be involved as surrogate informants when necessary for health-care professionals to detect depression while more caution is advised for what concerns anxiety and the coping strategies enacted by patients.

Microsomal membrane proteome of low grade diffuse astrocytomas: Differentially expressed proteins and candidate surveillance biomarkers

Diffuse astrocytoma (DA; WHO grade II) is a low-grade, primary brain neoplasm with high potential of recurrence as higher grade malignant form. We have analyzed differentially expressed membrane proteins from these tumors, using high-resolution mass spectrometry. A total of 2803 proteins were identified, 340 of them differentially expressed with minimum of 2 fold change and based on ≥2 unique peptides. Bioinformatics analysis of this dataset also revealed important molecular networks and pathways relevant to tumorigenesis, mTOR signaling pathway being a major pathway identified. Comparison of 340 differentially expressed proteins with the transcript data from Grade II diffuse astrocytomas reported earlier, revealed about 190 of the proteins correlate in their trends in expression. Considering progressive and recurrent nature of these tumors, we have mapped the differentially expressed proteins for their secretory potential, integrated the resulting list with similar list of proteins from anaplastic astrocytoma (WHO Grade III) tumors and provide a panel of proteins along with their proteotypic peptides, as a resource that would be useful for investigation as circulatory plasma markers for post-treatment surveillance of DA patients.