Current treatment of low grade astrocytoma: a review

Unraveling the signaling mechanism behind astrocytoma and possible therapeutics strategies: A comprehensive review

BACKGROUND

A form of cancer called astrocytoma can develop in the brain or spinal cord and sometimes causes death. A detailed overview of the precise signaling cascade underlying astrocytoma formation has not yet been revealed, although various factors have been investigated. Therefore, our objective was to unravel and summarize our current understanding of molecular genetics and associated signaling pathways with some possible therapeutic strategies for astrocytoma.

RECENT FINDINGS

In general, four different forms of astrocytoma have been identified in individuals, including circumscribed, diffuse, anaplastic, and multiforme glioblastoma, according to a recent literature review. All types of astrocytoma have a direct connection with some oncogenic signaling cascade. Common signaling is MAPK cascade, including Ras-Raf-ERK, up-regulated with activating EGFR/AKT/PTEN/mTOR and PDGFR. Recent breakthrough studies found that BRAF mutations, including KIAA1549: BRAF and BRAF V600E are responsible for astrocytoma progression. Additionally, cancer progression is influenced by mutations in some tumor suppressor genes, such as the Tp53/ATRX and MGMT mutant. As synthetic medications must cross the blood-brain barrier (BBB), modulating signal systems such as miRNA is the primary option for treating patients with astrocytoma. However, available surgery, radiation therapy, and experimental therapies such as adjuvant therapy, anti-angiogenic therapy, and EGFR-targeting antibody drug are the usual treatment for most types of astrocytoma. Similar to conventional anticancer medications, some phytochemicals slow tumor growth by simultaneously controlling several cellular proteins, including those involved in cell cycle regulation, apoptosis, metastatic spread, tyrosine kinase, growth factor receptor, and antioxidant-related proteins.

CONCLUSION

In conclusion, cellular and molecular signaling is directly associated with the development of astrocytoma, and a combination of conventional and alternative therapies can improve the malignancy of cancer patients.

Robustness of the wide-field imaging Mueller polarimetry for brain tissue differentiation and white matter fiber tract identification in a surgery-like environment: an ex vivo study

During neurooncological surgery, the visual differentiation of healthy and diseased tissue is often challenging. Wide-field imaging Muller polarimetry (IMP) is a promising technique for tissue discrimination and in-plane brain fiber tracking in an interventional setup. However, the intraoperative implementation of IMP requires realizing imaging in the presence of remanent blood, and complex surface topography resulting from the use of an ultrasonic cavitation device. We report on the impact of both factors on the quality of polarimetric images of the surgical resection cavities reproduced in fresh animal cadaveric brains. The robustness of IMP is observed under adverse experimental conditions, suggesting a feasible translation of IMP for in vivo neurosurgical applications.

The role of extent of resection on the prognosis of low-grade astrocytoma: a systematic review and meta-analysis

Purpose

To investigate the predictor factors of mortality describing the prognosis of primary surgical resection of low-grade astrocytoma.

Materials and methods

A systemic search was conducted from electronic databases (PubMed/Medline, Cochrane Library, and Google Scholar) from inception to November 14, 2021. All statistical analysis was conducted in Review Manager 5.4.1. Studies meeting inclusion criteria were selected. A random-effect model was used when heterogeneity was seen to pool the studies, and the result were reported in the hazards ratio (HR) and corresponding 95% confidence interval.

Result

Five cohort studies were selected for meta-analysis. There was statistically significant effect of total resection on increase mortality after surgery in low-grade astrocytoma patients (HR = 0.70 [0.52, 0.94]; p = 0.02; I2 = Not applicable). On the other hand, there was statistically nonsignificant effect of patient’s age (HR = 1.27 [0.95, 1.68]; p = 0.11; I2 = 83%), tumor size (HR = 1.13 [0.94, 1.35]; p = 0.19; I2 = 73%), and increasing KPS (HR = 0.59 [0.20, 1.77]; p = 0.35; I2 = 86%) on prognosis of low-grade astrocytoma after surgery.

Conclusion

The results of meta-analysis showed significant relationship of extent of resection and mortality, while factors such age, KPS score, and tumor size were nonsignificant to determine mortality in patient diagnosed with low-grade astrocytoma. The gross total resection surgery should be preferred over subtotal resection since the incidence of malignant formation is low in gross total resection.

Brain Tumor Causes, Symptoms, Diagnosis and Radiotherapy Treatment

The strategy used for the treatment of given brain cancer is critical in determining the post effects and survival. An oncological diagnosis of tumor evaluates a range of parameters such as shape, size, volume, location and neurological complexity that define the symptomatic severity. The evaluation determines a suitable treatment approach chosen from a range of options such as surgery, chemotherapy, hormone therapy, radiation therapy and other targeted therapies. Often, a combination of such therapies is applied to achieve superior results. Radiotherapy serves as a better treatment strategy because of a higher survival rate. It offers the flexibility of synergy with other treatment strategies and fewer side effects on organs at risk. This review presents a radiobiological perspective in the treatment of brain tumor. The cause, symptoms, diagnosis, treatment, post-treatment effects and the framework involved in its elimination are summarized.

CD47 is highly expressed in gliomas and targeting CD47 is a promising therapeutic strategy

Gliomas are very malignant brain tumors that are difficult to treat. CD47 is an antiphagocytic molecule that binds to SIPRα on phagocytes. It is overexpressed on the plasma membranes of multiple human tumor cell types and is an important diagnostic and prognostic biomarker in many types of cancer. However, the association between CD47 protein expression in glioma tissue and clinicopathological stage has not been investigated in detail. A total of 80 surgical glioma specimens were stained with anti-CD47 antibody to assess the relationship between CD47 protein expression and clinicopathological stage of the glioma. Wound healing assays were performed to analyze the influence of CD47 on the migration and invasion of glioma cells, and near-infrared fluorescence localization assays in a U-87 MG-bearing xenograft model were used to determine the distribution of anti-CD47 antibody in vivo. MTT assays and administration of anti-CD47 to a U251-bearing xenograft model were used to analyze the inhibitory effects of the antibody on gliomas. CD47 expression was higher in high-grade gliomas than in low-grade gliomas, and high CD47 expression was positively correlated with histology and tumor clinicopathological stage. CD47 over-expression promoted the growth and motility of two glioma cell lines (U-87 MG and U251) and a laboratory-developed anti-CD47 antibody accumulated at the glioma site. Proliferation of U251 and U-87 MG cells was not significantly inhibited by the anti-CD47 antibody in vitro, but the antibody significantly inhibited U251 growth in vivo. It also enhanced inhibition capacity by Taxol. Our results suggest that CD47 plays a critical role in the progression of gliomas from stage I to IV and may be a potential target for the treatment of gliomas. CD47 appears to play a critical role in the progression of gliomas from stage I to IV and an anti-CD47 antibody prepared in the laboratory may inhibit the growth of gliomas.

Bibliometric analysis of the top 100 most-cited articles on astrocytoma

Background

Citation analysis reflects the scientific recognition and influential performance of a published article within its field. We aim to identify the top 100 most-cited articles on astrocytoma using this bibliometric analysis method.

Methods

In May 2020, we performed a thorough search in the Scopus database using the word "Astrocytoma." The top 100 most-cited articles were arranged based on citation count in descending order. The resultant articles were then analyzed with an assessment of pertinent factors.

Results

The most-cited articles on astrocytoma had been cited 23,720 times. The top-cited article received a total of 682 citations, with an average of 34.1 citations annually. The list comprised eight clinical trials, in which the highest cited article received 625 citations. Articles were published from 1975 to 2015 with the 1995-2005 era as the most prolific period. Neuropathology studies were the most studied category, followed by clinical studies. The United States of America was the most significant contributor, with 49 published articles. The University of California San Francisco was the most contributing institution by producing 11 articles. Articles were published in 32 different journals led by the Cancer Research Journal, with a total of 12 publications. Approximately 160 authors contributed to the list in which Scheithauer, B.W. contributed the most with a total of eight articles.

Conclusion

This report clustered the most impactful articles on astrocytoma. It serves as an adequate tool to identify publication trends and helps in achieving evidence-based clinical practice.

Visualization of White Matter Fiber Tracts of Brain Tissue Sections With Wide-Field Imaging Mueller Polarimetry

Identification of white matter fiber tracts of the brain is crucial for delineating the tumor border during neurosurgery. A custom-built Mueller polarimeter was used in reflection configuration for the wide-field imaging of thick sections of fixed human brain and fresh calf brain. The maps of the azimuth of the fast optical axis of linear birefringent medium reconstructed from the experimental Mueller matrix images of the specimen by applying a non-linear data compression algorithm showed a strong correlation with the silver-stained sample histology image, which is the gold standard for ex-vivo brain fiber tract visualization. The polarimetric maps of fresh calf brain tissue demonstrated the same trends in the depolarization, the scalar retardance and the azimuth of the fast optical axis as seen in fixed human brain tissue. Thus, label-free imaging Mueller polarimetry shows promise as an efficient intra-operative modality for the visualization of healthy brain white matter fiber tracts, which could improve the accuracy of tumor border detection and, ultimately, patient outcomes.

OSlgg: An Online Prognostic Biomarker Analysis Tool for Low-Grade Glioma

Glioma is the most frequent primary brain tumor that causes high mortality and morbidity with poor prognosis. There are four grades of gliomas, I to IV, among which grade II and III are low-grade glioma (LGG). Although less aggressive, LGG almost universally progresses to high-grade glioma and eventual causes death if lacking of intervention. Current LGG treatment mainly depends on surgical resection followed by radiotherapy and chemotherapy, but the survival rates of LGG patients are low. Therefore, it is necessary to use prognostic biomarkers to classify patients into subgroups with different risks and guide clinical managements. Using gene expression profiling and long-term follow-up data, we established an Online consensus Survival analysis tool for LGG named OSlgg. OSlgg is comprised of 720 LGG cases from two independent cohorts. To evaluate the prognostic potency of genes, OSlgg employs the Kaplan-Meier plot with hazard ratio and p value to assess the prognostic significance of genes of interest. The reliability of OSlgg was verified by analyzing 86 previously published prognostic biomarkers of LGG. Using OSlgg, we discovered two novel potential prognostic biomarkers (CD302 and FABP5) of LGG, and patients with the elevated expression of either CD302 or FABP5 present the unfavorable survival outcome. These two genes may be novel risk predictors for LGG patients after further validation. OSlgg is public and free to the users at http://bioinfo.henu.edu.cn/LGG/LGGList.jsp.

The Expressional Pattern of Invasion-Related Extracellular Matrix Molecules in CNS Tumors

Aim of the study: Astrocytomas are primary CNS malignancies which infiltrate the peritumoral tissue, even when they are low-grade. Schwannomas are also primary CNS tumors, however, they do not show peritumoral infiltration similarly to brain metastases which almost never invade the neighboring parts of brain. Extracellular matrix is altered in composition in various cancer types and is proposed to play an important role in the development of invasiveness of astrocytic tumors. This study aims to identify differences in the ECM composition of CNS tumors with different invasiveness.Materials and methods: The mRNA and protein levels of ECM components were measured by QRT-PCR and mass-spectrometry, respectively, in grade II astrocytoma, NSCLC brain metastasis, schwannomas, and non-tumor brain control samples. Expressional data was analyzed statistically with ANOVA and nearest neighbor search.Results: There is a significant difference in the expressional pattern of invasion-related ECM components among various CNS tumors, especially among those of different embryonic origin. Non-invasive tumors show only slight differences in the expressional pattern of ECM molecules. Tumor samples can be separated based on their expressional pattern using statistical classifiers, therefore the ECM composition seems to be typical of various cancer types.Conclusions: Differences in the expressional pattern of the ECM could be responsible for the different invasiveness of various CNS tumors.

Diagnostic Performance of Arterial Spin Labeling for Grading Nonenhancing Astrocytic Tumors

Purpose:

We evaluated the utility of arterial spin labeling (ASL) imaging of tumor blood flow (TBF) for grading non-enhancing astrocytic tumors.

Materials and Methods:

Thirteen non-enhancing astrocytomas were divided into high-grade (n = 7) and low-grade (n = 6) groups. Both ASL and conventional sequences were acquired using the same magnetic resonance machine. Intratumoral absolute maximum TBF (TBF_max), absolute mean TBF (TBF_mean), and corresponding values normalized to cerebral blood flow (TBF_max and TBF_mean ratios) were measured. The Mann-Whitney U test and receiver operating characteristic (ROC) curve analysis were used to assess the accuracy of TBF variables for tumor grading.

Results:

Compared with low-grade astrocytoma, high-grade astrocytoma exhibited significantly greater absolute TBF_max (90.93 ± 24.96 vs 46.94 ± 20.97 ml/100 g/min, P < 0.001), TBF_mean (58.75 ± 19.89 vs 31.16 ± 17.63 ml/100 g/min, P < 0.001), TBF_max ratio (3.34 ± 1.22 vs 1.35 ± 0.5, P < 0.001), and TBF_mean ratio (2.15 ± 0.94 vs 0.88 ± 0.41, P < 0.001). The TBF_max ratio yielded the highest diagnostic accuracy (sensitivity 100%, specificity 86.3%), while absolute TBF_mean yielded the lowest accuracy (sensitivity 85.7%, specificity 70.1%) by ROC analysis.

Conclusion:

Parameters from ASL perfusion imaging, particularly TBF_max ratio, may be useful for distinguishing high-grade from low-grade astrocytoma in cases with equivocal conventional MRI findings.

Identification of a gene signature associated with radiotherapy and prognosis in gliomas

Glioma is one of the most common primary brain tumors with poor prognosis. Although radiotherapy is an important treatment method for gliomas, the efficacy is still limited by the high occurrence of radioresistance and the underlying molecular mechanism is unclear. Here, we performed a data mining work based on four glioma expression datasets. These datasets were classified into training set and validation set. Radiotherapy-induced differential expressed genes and prognosis-associated genes were screened using different classifiers. The Kaplan-Meier curves along with the two-sided Log Rank (Mantel-Cox) test were used to evaluate overall survival. We found the gene expression profiles of gliomas between those patients received radiotherapy and those patients without received radiotherapy were quite different. A 20-gene signature was identified, which was associated with radiotherapy.Furthermore, a novel 5-gene signature (HOXC10, LOC101928747, CYB561D2, RPL36A and RPS4XP2) as an independent predictor of glioma patients’ prognosis was further derived from the 20-gene signature. These findings provided a new insight into the molecular mechanism of radioresistance in gliomas. The 5-gene signature might represent therapeutic target for gliomas.

Convex-Envelope Based Automated Quantitative Approach to Multi-Voxel 1H-MRS Applied to Brain Tumor Analysis

Background

Magnetic Resonance Spectroscopy (MRS) can measure in vivo brain tissue metabolism that exhibits unique biochemical characteristics in brain tumors. For clinical application, an efficient and versatile quantification method of MRS would be an important tool for medical research, particularly for exploring the scientific problem of tumor monitoring. The objective of our study is to propose an automated MRS quantitative approach and assess the feasibility of this approach for glioma grading, prognosis and boundary detection.

Methods

An automated quantitative approach based on a convex envelope (AQoCE) is proposed in this paper, including preprocessing, convex-envelope based baseline fitting, bias correction, sectional baseline removal, and peak detection, in a total of 5 steps. Some metabolic ratios acquired by this quantification are selected for statistical analysis. An independent sample t-test and the Kruskal-Wallis test are used for distinguishing low-grade gliomas (LGG) and high-grade gliomas (HGG) and for detecting the tumor, peritumoral and contralateral areas, respectively. Seventy-eight cases of pre-operative brain gliomas with pathological reports are included in this study.

Results

Cho/NAA, Cho/Cr and Lip-Lac/Cr (LL/Cr) calculated by AQoCE in the tumor area differ significantly between LGG and HGG, with p≤0.005. Using logistic regression combining Cho/NAA, Cho/Cr and LL/Cr to generate a ROC curve, AQoCE achieves a sensitivity of 92.9%, a specificity of 72.2%, and an area under ROC curve (AUC) of 0.860. Moreover, both Cho/NAA and Cho/Cr in the AQoCE approach show a significant difference (p≤0.019) between tumoral, peritumoral, and contralateral areas. The comparison between the results of AQoCE and Siemens MRS processing software are also discussed in this paper.

Conclusions

The AQoCE approach is an automated method of residual water removal and metabolite quantification. It can be applied to multi-voxel ¹H-MRS for evaluating brain glioma grading and demonstrating characteristics of brain glioma metabolism. It can also detect infiltration in the peritumoral area. Under the limited clinical data used, AQoCE is significantly more versatile and efficient compared to the reference approach of Siemens.

Expression Profile of MiR-128 in the Astrocytoma Patients and Cell Lines

Malignant astrocytomas are the most common primary brain tumors. The critical characterizes of astrocyomas are their aggressive and infiltrative in the brain, which leads to uncontrollable by conventional forms of therapy. MicroRNAs are small RNAs that had been found to regulate their targets by specific binding to the 3'-untranslated region (3'UTR) of mRNA. Recent advances in understanding the molecular biology of these tumors have revealed that microRNA (miRNA) disruption may play important roles in the pathogenesis of astrocytomas. And some of the miRNA alterations were found in the serum of astrocytoma patients. In this study, we studied the expression profile of miR-128, in the different stages of astrocytoma tissues and two human astrocytoma cell lines, A172 and T98G cells. We found that the levels of miR-128 are decreased in the A172 and T98G cells when compared to normal human astrocyte (NHA). Furthermore, the levels of miR-128 decreased gradually to the pathological stages of astrocytomas. We also identified that TROVE2 is a novel target of miR-128 by the luciferase reporter system. Furthermore, the expression levels of TROVE2 are dramatically increased with the pathological stages increasing. Finally, the levels of TROVE2 are negatively correlated with miR-128 in astrocytoma tissues. Our data provided novel evidence for the miR-128 and TROVE2 in the development of human astrocytomas.

Survival trends of grade I, II, and III astrocytoma patients and associated clinical practice patterns between 1999 and 2010: A SEER-based analysis

Background

The survival trends and the patterns of clinical practice pertaining to radiation therapy and surgical resection for WHO grade I, II, and III astrocytoma patients remain poorly characterized.

Methods

Using the Surveillance, Epidemiology and End Results (SEER) database, we identified 2497 grade I, 4113 grade II, and 2755 grade III astrocytomas during the period of 1999-2010. Time-trend analyses were performed for overall survival, radiation treatment (RT), and the extent of surgical resection (EOR).

Results

While overall survival of grade I astrocytoma patients remained unchanged during the study period, we observed improved overall survival for grade II and III astrocytoma patients (Tarone-Ware P < .05). The median survival increased from 44 to 57 months and from 15 to 24 months for grade II and III astrocytoma patients, respectively. The differences in survival remained significant after adjusting for pertinent variables including age, ethnicity, marital status, sex, tumor size, tumor location, EOR, and RT status. The pattern of clinical practice in terms of EOR for grade II and III astrocytoma patients did not change significantly during this study period. However, there was decreased RT utilization as treatment for grade II astrocytoma patients after 2005.

Conclusion

Results from the SEER database indicate that there were improvements in the overall survival of grade II and III astrocytoma patients over the past decade. Analysis of the clinical practice patterns identified potential opportunities for impacting the clinical course of these patients.

Second chances

An 81-year-old woman presented with light perception vision in her left eye and had pallid swelling of the left optic disk. Temporal artery biopsy was normal. Magnetic resonance imaging revealed enlargement and enhancement of the left orbital optic nerve. There were vitreous cells, but a vitrectomy specimen showed only a benign lymphocytic population. Her vision deteriorated to no light perception in the left eye, and an optic nerve biopsy revealed a diffuse astrocytoma of World Health Organization grade II.

A radiosensitivity gene signature in predicting glioma prognostic via EMT pathway

A 31-gene signature derived by integrating four different microarray experiments, has been found to have a potential for predicting radiosensitivity of cancer cells, but it was seldom validated in clinical cancer samples. We proposed that the gene signature may serve as a predictive biomarker for estimating the overall survival of radiation-treated patients. The significance of gene signature was tested in two previously published datasets from Gene Expression Omnibus (GEO) and The Cancer Genome Altas (TCGA), respectively. In GEO data set, patients predicted to be radiosensitive(RS) had an improved overall survival when compared with radioresistant(RR) patients in either radiotherapy(RT)-treated or non radiotherapy(RT)-treated subgroups(p<0.0001 in the RT-treated group). Multivariate Cox regression analysis showed that the gene signature is the strongest predictor(p=0.0093) in the RT-treated subgroup of patients. However, it does not remain significant (p=0.7668) in non radiotherapy-treated group when adjusting for age and Karnofsky performance score (KPS) as covariates. Similarly, in the TCGA data set, radiotherapy-treated glioblastoma multiforme(GBM) patients assigned to RS group had an improved overall survival compared with RR group(p<0.0001). Geneset enrichment analysis(GSEA) analysis revealed that enrichment of epithelial mesenchymal transition(EMT) pathway was observed with radioresistant phenotype. These results suggest that the signature is a predictive biomarker for radiation-treated glioma patients' prognostic.

Volumetric modulated arc therapy for hippocampal-sparing radiotherapy in transformed low-grade glioma: A treatment planning case report

Timing of radiotherapy for low-grade gliomas is still controversial due to concerns of possible adverse late effects. Prevention of possible late cognitive sequelae by hippocampal avoidance has shown promise in phase II trials. A patient with progressive low-grade glioma with gradual dedifferentiation into anaplastic astrocytoma is presented along with description of radiotherapy planning process attempting to spare the hippocampus. To our knowledge, this is the first described case using volumetric modulated arc technique to spare hippocampus during transformed low-grade glioma radiotherapy. Using modern intensity-modulated radiotherapy systems it is possible to selectively spare hippocampus together with other standard organs at risk. For selected patients, an attempt to spare hippocampus can be considered as long as other dose characteristics are not significantly compromised compared to standard treatment plan created without any effort to avoid hippocampus.

Treatment of epileptic seizures in brain tumors: a critical review

Epileptic seizures represent a common signal of intracranial tumors, frequently the presenting symptom and the main factor influencing quality of life. Treatment of tumors concentrates on survival; antiepileptic drug (AED) treatment frequently is prescribed in a stereotyped way. A differentiated approach according to epileptic syndromes can improve seizure control and minimize unwarranted AED effects. Prophylactic use of AEDs is to be discouraged in patients without seizures. Acutely provoked seizures do not need long-term medication except for patients with high recurrence risk indicated by distinct EEG patterns, auras, and several other parameters. With chronically repeated seizures (epilepsies), long-term AED treatment is indicated. Non-enzyme-inducing AEDs might be preferred. Valproic acid exerts effects against progression of gliomatous tumors. In low-grade astrocytomas with epilepsy, a comprehensive presurgical epilepsy work-up including EEG-video monitoring is advisable; in static non-progressive tumors, it is mandatory. In these cases, the neurosurgical approach has to include the removal of the seizure-onset zone frequently located outside the lesion.

Gliomas: application of cumulative histogram analysis of normalized cerebral blood volume on 3 T MRI to tumor grading

Background

Glioma grading assumes significant importance in that low- and high-grade gliomas display different prognoses and are treated with dissimilar therapeutic strategies. The objective of our study was to retrospectively assess the usefulness of a cumulative normalized cerebral blood volume (nCBV) histogram for glioma grading based on 3 T MRI.

Methods

From February 2010 to April 2012, 63 patients with astrocytic tumors underwent 3 T MRI with dynamic susceptibility contrast perfusion-weighted imaging. Regions of interest containing the entire tumor volume were drawn on every section of the co-registered relative CBV (rCBV) maps and T2-weighted images. The percentile values from the cumulative nCBV histograms and the other histogram parameters were correlated with tumor grades. Cochran’s Q test and the McNemar test were used to compare the diagnostic accuracies of the histogram parameters after the receiver operating characteristic curve analysis. Using the parameter offering the highest diagnostic accuracy, a validation process was performed with an independent test set of nine patients.

Results

The 99th percentile of the cumulative nCBV histogram (nCBV C99), mean and peak height differed significantly between low- and high-grade gliomas (P = <0.001, 0.014 and <0.001, respectively) and between grade III and IV gliomas (P = <0.001, 0.001 and <0.001, respectively). The diagnostic accuracy of nCBV C99 was significantly higher than that of the mean nCBV (P = 0.016) in distinguishing high- from low-grade gliomas and was comparable to that of the peak height (P = 1.000). Validation using the two cutoff values of nCBV C99 achieved a diagnostic accuracy of 66.7% (6/9) for the separation of all three glioma grades.

Conclusion

Cumulative histogram analysis of nCBV using 3 T MRI can be a useful method for preoperative glioma grading. The nCBV C99 value is helpful in distinguishing high- from low-grade gliomas and grade IV from III gliomas.