Glioma

The term “glioma” could technically be used to refer to all tumors of any glial lineage (i.e., from glial cells such as oligodendroglia, ependymal cells, Schwann cells, microglia…), but in its common usage, “glioma” usually refers only to astrocytic tumors.

Gliomas comprise a heterogeneous group of benign and malignant neoplasms.

The body of glioma-related literature has grown significantly over the past 25 years. Despite this growth in the amount of published research, gliomas remain one of the most intransigent cancers. The purpose of a study was to analyze the landscape of glioma-related research over the past 25 years using machine learning and text analysis.

In April 2019, Feng et al. downloaded glioma-related publications indexed in PubMed between 1994 and 2018. They used Python to extract the title, publication date, MeSH terms, and abstract from the metadata of each publication for bibliometric assessment. Latent Dirichlet allocation (LDA) was applied to the abstracts to identify publications’ research topics with greater specificity.

They identified and analyzed a total of 52,625 publications. They found that research on prognosis and the treatment of glioblastoma increased the most in terms of volume and rate of publications over the past 25 years. However, publications regarding clinical trials accounted for <5% of all publications considered in this study. The current research landscape covers clinical, pre-clinical, biological, and technical aspects of glioblastoma; at present, researchers appear to be less concerned with glioblastoma’s psychological effects or patients’ end-of-life care.

Publication of glioma-related research has expanded rapidly over the past 25 years. Common topics include the disease’s molecular background, patients’ survival, and treatment outcomes; more research needs to be done on the psychological aspects of glioblastoma and end-of-life care ¹⁾

Studies on gliomas suggested that the microenvironment of human gliomas contains both glioma stem cells (GSCs) and glioma associated (GA)-mesenchymal stem cells (MSCs; (GA-MSCs). Also, studies have suggested that nano- sized vesicles, termed exosomes, have been recently observed to contribute towards intercellular communication within the tumor niche ²⁾.

Epidemiology

Gliomas are the second most common primary brain tumors, with an incidence of 4–5/100 000 individuals. Gliomas are the second leading cause of cancer mortality in adults under the age of 35, the fourth leading cause in those under the age of 54, and result in death in approximately 13 770 individuals per year in the United States.

Approximately 89,000 new primary brain tumors are diagnosed in the United States each year, for which 27% are gliomas and 32.8% are malignant gliomas ³⁾.

The are more frequent among males ⁴⁾.

Classification

They encompass two principle subgroups: diffuse gliomas and gliomas showing a more circumscribed growth pattern (‘non-diffuse gliomas’). In the revised 4th edition of the World Health Organization Classification of Tumors of the Central Nervous System published in 2016, classification of especially diffuse gliomas has fundamentally changed: for the first time a large subset of these tumours is now defined based on presence/absence of IDH mutation and 1p/19q codeletion. Following this approach, the diagnosis of (anaplastic) oligoastrocytoma can be expected to largely disappear ⁵⁾.

see Glioma classification.

Sorting and grading of glial tumors by the WHO grade classification provide clinicians with guidance as to the predicted course of the disease and choice of treatment. Nonetheless, histologically identical tumors may have very different outcome and response to treatment. Molecular biomarkers that carry both diagnostic and prognostic information add useful tools to traditional classification by redefining tumor subtypes within each WHO category. Therefore, molecular markers have become an integral part of tumor assessment in modern neurooncology and biomarker status now guides clinical decisions in some subtypes of gliomas. The routine assessment of IDH status improves histological diagnostic accuracy by differentiating diffuse glioma from reactive gliosis. It carries a favorable prognostic implication for all glial tumors and it is predictive for chemotherapeutic response in anaplastic oligodendrogliomas with codeletion of 1p19q chromosomes. Glial tumors that contain chromosomal codeletion of 1p/19q are defined as tumors of oligodendroglial lineage and have favorable prognosis. MGMT promoter methylation is a favorable prognostic marker in astrocytic high-grade gliomas and it is predictive for chemotherapeutic response in anaplastic gliomas with wild-type IDH1/2 and in elderly glioblastoma ⁶⁾.

Pathogenesis

see Gliomagenesis

Spread

see Glioma spread

Clinical Features

Many gliomas become symptomatic with either seizures or focal neurological deficits and are subsequently detected via MRI.

Diagnosis

see Glioma Diagnosis.

MRI

see MRI for glioma.

Treatment

see Glioma treatment.

Outcome

see Glioma outcome.

Books

see Glioma Books.

Case series

Glioma case series.

References