Innovations in the Diagnosis and Surgical Management of Low-Grade Gliomas

Quantifying H&E staining results, grading and predicting IDH mutation status of gliomas using hybrid multi-dimensional MRI

OBJECTIVE

To assess the performance of hybrid multi-dimensional magnetic resonance imaging (HM-MRI) in quantifying hematoxylin and eosin (H&E) staining results, grading and predicting isocitrate dehydrogenase (IDH) mutation status of gliomas.

MATERIALS AND METHODS

Included were 71 glioma patients (mean age, 50.17 ± 13.38 years; 35 men). HM-MRI images were collected at five different echo times (80-200 ms) with seven b-values (0-3000 s/mm2). A modified three-compartment model with very-slow, slow and fast diffusion components was applied to calculate HM-MRI metrics, including fractions, diffusion coefficients and T2 values of each component. Pearson correlation analysis was performed between HM-MRI derived fractions and H&E staining derived percentages. HM-MRI metrics were compared between high-grade and low-grade gliomas, and between IDH-wild and IDH-mutant gliomas. Using receiver operational characteristic (ROC) analysis, the diagnostic performance of HM-MRI in grading and genotyping was compared with mono-exponential models.

RESULTS

HM-MRI metrics FDvery-slow and FDslow demonstrated a significant correlation with the H&E staining results (p < .05). Besides, FDvery-slow showed the highest area under ROC curve (AUC = 0.854) for grading, while Dslow showed the highest AUC (0.845) for genotyping. Furthermore, a combination of HM-MRI metrics FDvery-slow and T2Dslow improved the diagnostic performance for grading (AUC = 0.876).

DISCUSSION

HM-MRI can aid in non-invasive diagnosis of gliomas.

Pan-cancer analysis of ADAR1 with its prognostic relevance in low-grade glioma

ADAR1, known as the primary enzyme for adenosine-to-inosine RNA editing, has recently been implicated in cancer development through both RNA editing-dependent and -independent pathways. These discoveries suggest that ADAR1's functions may extend beyond our current understanding. A pan-cancer analysis offers a unique opportunity to identify both common and distinct mechanisms across various cancers, thereby advancing personalized medicine. Low-grade glioma (LGG), characterized by a diverse group of tumor cells, presents a challenge in risk stratification, leading to significant variations in treatment approaches. Recently discovered molecular alterations in LGG have helped to refine the stratification of of these tumors and offered novel targets for predicting likely outcomes. This study aims to provide a detailed analysis of ADAR mRNA across multiple cancers, emphasizing its prognostic significance in LGG. We observed inconsistent mRNA and consistent protein expression patterns of ADAR1/ADAR in pan-cancer analyses that across tumor types. ADAR mRNA expression did not always correlate with ADAR1 protein expression. Nevertheless, the transcript levels correlated significantly with genetic alterations, tumor mutation burden, microsatellite instability, overall survival, recurrence-free survival, immune marker presence, immune infiltration, and the survival of patients undergoing immunotherapy in select cancers. Furthermore, ADAR and its top 50 associated genes were primarily involved in mRNA-related events, as identified through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. Utilizing the Cox proportional hazards model, we developed a 3-gene signature (ADAR, HNRNPK, and SMG7), which effectively stratified patients into high- and low-risk groups, with high-risk patients exhibiting poorer overall survival, higher tumor grades, and a greater number of non-codeletions. Overall, this signature was inversely related to immune infiltration across cancers. Transcription factor SPI1 and miR-206, potential upstream regulators of the signature genes, were closely linked to patient survival in LGG. The promoter regions of these genes were hypermethylated, further associating them with patient outcomes. Additionally, these genes displayed consistent drug susceptibility patterns. In conclusion, our findings reveal multiple aspects of ADAR1's role in cancer and underscore its prognostic value in LGG, offering insights into potential therapeutic targets and strategies.

Foundations of the Diagnosis and Management of Low-Grade Gliomas

In the past, low-grade gliomas-World Health Organization (WHO) grade I and II tumors-were generally expected to have a much better prognosis than higher-grade (WHO grade III and IV) gliomas. However, diffuse gliomas (WHO grade II), unlike WHO grade I gliomas, are by definition infiltrative, limiting resection and potentially contributing to poor outcomes like those seen with malignant gliomas. Rapid progress in the understanding of the pathogenesis of these tumors indicates that specific molecular factors, especially isocitrate dehydrogenase mutation status and the presence or absence of the 1p/19q codeletion (deletion of the short arm of chromosome 1 and long arm of chromosome 19), are much more important than grade in determining prognosis and response to treatment. These molecular characteristics outweigh the histologic distinctions and have been quickly incorporated into the WHO classification of gliomas. Management of these tumors with surgery, radiation, and chemotherapy has similarly been transformed by these developments, highlighting the need for a customized approach for patients with low-grade gliomas.

Challenges in the Diagnosis and Management of Low-Grade Gliomas

Low-grade gliomas are clinically challenging entities. Patients with these tumors tend to be relatively young at presentation, and lesions are often incidental findings or are identified because the patient presents with a seizure. Rapidly emerging and evolving molecular classifications of gliomas have influenced treatment paradigms. Importantly, low-grade gliomas can be classified on the basis of IDH mutation status, whereby low-grade astrocytomas harbor the IDH mutation, while oligodendrogliomas are defined by both IDH mutant status and 1p/19q co-deletion. Given the importance of molecular classification for diagnosis, treatment planning, and prognostication, tissue samples are necessary for proper management. Literature supports improved overall survival and outcomes with increased extent of resection for low-grade glioma. Awake craniotomies and resection of insular low-grade gliomas both have been demonstrated as safe and improve outcomes for patients with lesions located in eloquent areas. Given the younger age at diagnosis of these lesions compared with higher-grade gliomas, fertility, fertility preservation, and potential malignant transformation should be discussed with patients of childbearing age.