Recurrent ganglioglioma in adults treated with BRAF inhibitors

Pediatric-type low-grade gliomas in adolescents and young adults-challenges and emerging paradigms

Pediatric-type low-grade glioma (PLGG) encompasses a heterogeneous group of WHO grade 1 or 2 tumors and is the most common central nervous system tumor found in children. PLGG extends beyond pediatrics, into adolescents and young adults (AYA, ages 15-40). PLGG represents 25% of all gliomas diagnosed in AYA with differences in tumor location and molecular alterations compared to children, resulting in improved outcome for AYAs. Long-term outcome is excellent, though patients may suffer significant morbidity depending on tumor location. There are differences in treatment practices with radiation used to treat PLGG in AYAs more often than in children. Most PLGG in AYA harbor an alteration in the RAS/MAPK pathway, with limited insight into response to targeted therapy in this age group. This review discusses the epidemiology, current therapeutic approaches, and challenges in the management of PLGG in AYA.

A novel BRAF::PTPRN2 fusion in meningioma: a case report

Gene fusion events have been linked to oncogenesis in many cancers. However, gene fusions in meningioma are understudied compared to somatic mutations, chromosomal gains/losses, and epigenetic changes. Fusions involving B-raf proto-oncogene, serine/threonine kinase (BRAF) are subtypes of oncogenic BRAF genetic abnormalities that have been reported in certain cases of brain tumors, such as pilocytic astrocytomas. However, BRAF fusions have not been recognized in meningioma. We present the case of an adult female presenting with episodic partial seizures characterized by déjà vu, confusion, and cognitive changes. Brain imaging revealed a cavernous sinus and sphenoid wing mass and she underwent resection. Histopathology revealed a World Health Organization (WHO) grade 1 meningioma. Genetic profiling with next generation sequencing and microarray analysis revealed an in-frame BRAF::PTPRN2 fusion affecting the BRAF kinase domain as well as chromothripsis of chromosome 7q resulting in multiple segmental gains and losses including amplifications of cyclin dependent kinase 6 (CDK6), tyrosine protein-kinase Met (MET), and smoothened (SMO). Elevated pERK staining in tumor cells provided evidence of activated mitogen-activated protein kinase (MAPK) signaling. This report raises the possibility that gene fusion events may be involved in meningioma pathogenesis and warrant further investigation.

Rare Neuronal, Glial and Glioneuronal Tumours in Adults

Rare glial, neuronal and glioneuronal tumours in adults form a heterogeneous group of rare, primary central nervous system tumours. These tumours, with a glial and/or neuronal component, are challenging in terms of diagnosis and therapeutic management. The novel classification of primary brain tumours published by the WHO in 2021 has significantly improved the diagnostic criteria of these entities. Indeed, diagnostic criteria are nowadays multimodal, including histological, immunohistochemical and molecular (i.e., genetic and methylomic). These integrated parameters have allowed the specification of already known tumours but also the identification of novel tumours for a better diagnosis.

Benign Glioma

Benign glioma broadly refers to a heterogeneous group of slow-growing glial tumors with low proliferative rates and a more indolent clinical course. These tumors may also be described as "low-grade" glioma (LGG) and are classified as WHO grade I or II lesions according to the Classification of Tumors of the Central Nervous System (CNS) (Louis et al. in Acta Neuropathol 114:97-109, 2007). Advances in molecular genetics have improved understanding of glioma tumorigenesis, leading to the identification of common mutation profiles with significant treatment and prognostic implications. The most recent WHO 2016 classification system has introduced several notable changes in the way that gliomas are diagnosed, with a new emphasis on molecular features as key factors in differentiation (Wesseling and Capper in Neuropathol Appl Neurobiol 44:139-150, 2018). Benign gliomas have a predilection for younger patients and are among the most frequently diagnosed tumors in children and young adults (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). These tumors can be separated into two clinically distinct subgroups. The first group is of focal, well-circumscribed lesions that notably are not associated with an increased risk of malignant transformation. Primarily diagnosed in pediatric patients, these WHO grade I tumors may be cured with surgical resection alone (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). Recurrence rates are low, and the prognosis for these patients is excellent (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). Diffuse gliomas are WHO grade II lesions with a more infiltrative pattern of growth and high propensity for recurrence. These tumors are primarily diagnosed in young adult patients, and classically present with seizures (Pallud et al. Brain 137:449-462, 2014). The term "benign" is a misnomer in many cases, as the natural history of these tumors is with malignant transformation and recurrence as grade III or grade IV tumors (Jooma et al. in J Neurosurg 14:356-363, 2019). For all LGG, surgery with maximal safe resection is the treatment of choice for both primary and recurrent tumors. The goal of surgery should be for gross total resection (GTR), as complete tumor removal is associated with higher rates of tumor control and seizure freedom. Chemotherapy and radiation therapy (RT), while not typically a component of first-line treatment in most cases, may be employed as adjunctive therapy in high-risk or recurrent tumors and in some select cases. The prognosis of benign gliomas varies widely; non-infiltrative tumor subtypes generally have an excellent prognosis, while diffusely infiltrative tumors, although slow-growing, are eventually fatal (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). This chapter reviews the shared and unique individual features of the benign glioma including diffuse glioma, pilocytic astrocytoma and pilomyxoid astrocytoma (PMA), subependymal giant cell astrocytoma (SEGA), pleomorphic xanthoastrocytoma (PXA), subependymoma (SE), angiocentric glioma (AG), and chordoid glioma (CG). Also discussed is ganglioglioma (GG), a mixed neuronal-glial tumor that represents a notable diagnosis in the differential for other LGG (Wesseling and Capper 2018). Ependymomas of the brain and spinal cord, including major histologic subtypes, are discussed in other chapters.

The landscape of common genetic drivers and DNA methylation in low-grade (epilepsy-associated) neuroepithelial tumors: A review

Low-grade neuroepithelial tumors (LNETs) represent an important group of central nervous system neoplasms, some of which may be associated to epilepsy. The concept of long-term epilepsy-associated tumors (LEATs) includes a heterogenous group of low-grade, cortically based tumors, associated to drug-resistant epilepsy, often requiring surgical treatment. LEATs entities can sometimes be poorly discriminated by histological features, precluding a confident classification in the absence of additional diagnostic tools. This study aimed to provide an updated review on the genomic findings and DNA methylation profiling advances in LNETs, including histological entities of LEATs. A comprehensive search strategy was conducted on PubMed, Embase, and Web of Science Core Collection. High-quality peer-reviewed original manuscripts and review articles with full-text in English, published between 2003 and 2022, were included. Results were screened based on titles and abstracts to determine suitability for inclusion, and when addressed the topic of the review was screened by full-text reading. Data extraction was performed through a qualitative content analysis approach. Most LNETs appear to be driven mainly by a single genomic abnormality and respective affected signaling pathway, including BRAF p.V600E mutations in ganglioglioma, FGFR1 abnormalities in dysembryoplastic neuroepithelial tumor, MYB alterations in angiocentric glioma, BRAF fusions in pilocytic astrocytoma, PRKCA fusions in papillary glioneuronal tumor, between others. However, these molecular alterations are not exclusive, with some overlap amongst different tumor histologies. Also, clustering analysis of DNA methylation profiles allowed the identification of biologically similar molecular groups that sometimes transcend conventional histopathological classification. The exciting developments on the molecular basis of these tumors reinforce the importance of an integrative histopathological and (epi)genetic classification, which can be translated into precision medicine approaches.

Prediction of BRAF mutation status in glioblastoma multiforme by preoperative ring enhancement appearances on MRI

Background

Ring enhancement on magnetic resonance imaging (MRI) is an important characteristic of GBM. Though patients suffering from glioblastoma multiforme (GBM) with BRAF mutation (MUT BRAF) in V600E benefit from BRAF-targeted inhibitors, the relationship between ring enhancement and MUT BRAF remains elusive. The purpose of this study was to investigate the relationship between BRAF mutation status and the appearance of ring enhancement so as to guide preoperative targeted therapy for MUT BRAF GBM.

Methods

Patient’s population, clinical data and characteristic ring enhancement appearances on MRI were compared between GBM with MUT BRAF and GBM with WT BRAF. A receiver operating characteristic (ROC) curve analysis was performed to evaluate the differential diagnostic significance. A nomogram was developed to predict the mutation status of BRAF. Moreover, all the variables were re-analyzed between epithelioid GBM (E-GBM) with or without MUT BRAF.

Results

Compared to GBM with WT BRAF, GBM with MUT BRAF had specific ring enhancement appearances with multiple rings, multiple located lobes, regular shape of ring, uniform thickness of ring and smaller diameter of ring. Area under the curve (AUC) of all the variables’ combination was 0.929. The nomogram was developed and validated. The re-analyzed results between E-GBM with or without MUT BRAF were similar to these above. AUC of the combination of quantity of ring, quantity of located lobe and shape of ring was 0.962.

Conclusion

The characteristic ring enhancement appearances of GBM may play an important role in predicting BRAF mutation status preoperatively, especially in E-GBM. Further study with larger cases may provide more evidences to guide the pretreatment of targeted medicine for GBM patients with MUT BRAF in future.

Effective treatment of a BRAF V600E-mutant epithelioid glioblastoma patient by vemurafenib: a case report

Epithelioid glioblastoma (E-GBM) is a recently described variant of glioblastoma (GBM) which is associated with short survival and now added as a provisional entity to WHO 2016 classification of central nervous system tumors. About half of these tumors show the BRAF mutant. Therefore, this is a target of special interest for this group of patients. Meanwhile, unlike conventional glioblastoma, E-GBM lacks specific prognostic markers. We described a case of a long-term surviving 37-years-old men patient diagnosed with a BRAF V600E and TERT mutated E-GBM with wild-type in the isocitrate dehydrogenase gene (IDH wild-type). The tumor displayed atypical exophytic growth, an obvious proliferation of vascular endothelial cells, especially tumor tissue can be seen under subarachnoid space. Notably, tumor tissue was found under subarachnoid space. After postoperative conventional treatment options were exhausted, vemurafenib treatment was initiated. The patient remained clinically stable, and follow-up magnetic resonance images were consistent with stable disease for the following fifteen months up to now. Whole-exome sequencing analysis and RNA-seq results of formalin-fixed and paraffin-embedded tissue revealed nine mutant genes (AHNAK2, BFSP1, BRAF, CNTNAP3, DNHD1, MTOR, NFATC3, NOM1). For E-GBM patients, the use of BRAF inhibitors combined with inhibitors of these seven genes may be a useful remedial treatment option.

Durable Progression-Free Survival With the Use of BRAF and MEK Inhibitors in Four Cases With BRAF V600E-Mutated Gliomas

INTRODUCTION

BRAF V600 E mutations have been identified in a subset of patients with primary brain tumors. Combination therapy with BRAF and Mitogen-activated protein kinase (MEK) inhibitors (BRAF/MEKi) targeting sequential steps in the MAPK pathway has replaced BRAFi monotherapy as the standard of care in multiple tumors with BRAF V600 E mutations, and clinical evidence for this strategy continues to grow in primary brain tumors.

CASE SERIES

We describe four patients with BRAF V600 E mutated gliomas, including a 21-year-old woman with a ganglioglioma WHO grade I, a 19-year-old man with a pleomorphic xanthoastrocytoma WHO grade III, and 21-year-old and 33-year-old women with epithelioid GBM WHO grade IV, who achieved durable progression-free survival with combination BRAF/MEKi.

CONCLUSION

Combination of BRAF/MEK inhibition can be a novel, promising approach as targeted therapy in gliomas with BRAF V600 E mutations, especially those that are resistant to standard therapy. Our cases, along with other early reports utilizing dabrafenib/trametinib, highlight the importance of somatic next-generation sequencing, particularly in younger patients. Interim results from clinical trials utilizing dabrafenib/trametinib have been promising thus far, and our case series suggests that durable clinical benefit is possible, even in the setting of glioblastoma, WHO grade IV.

Glioneuronal tumors: clinicopathological findings and treatment options

Glioneuronal tumors are very rare CNS neoplasms that demonstrate neuronal differentiation, composed of mixed glial and neuronal cells. The majority of these lesions are low grade and their correct classification is crucial in order to avoid misidentification as ‘ordinary’ gliomas and prevent inappropriate aggressive treatment; nevertheless, precise diagnosis is a challenge due to phenotypic overlap across different histologic subtype. Surgery is the standard of therapeutic approach; literature concerning the benefit of adjuvant treatments is inconclusive and a globally accepted treatment of recurrence does not exist. Targetable mutations in the genes BRAF and FGFR1/2 are recurrently found in these tumors and could take a promising role in future treatment management.

RAF and MEK inhibitor therapy in adult patients with brain tumors: a case-based overview and practical management of adverse events

Targeted therapy has gained mainstream attention with notable successes against specific genetic mutations in many cancers. One particular mutation, the BRAF V600E mutation, is present in a small subset of gliomas in adults. Although clinical experience and trial data of RAF-targeted therapy in adults with glioma are lacking at this time, the poor prognosis of adult high-grade glioma has led neuro-oncology practitioners to consider the use of targeted therapy in these patients. In this manuscript, we describe the use of RAF and MEK inhibitors in adults with recurrent glioma. We discuss the utility of these agents, describe their toxicities, and give examples of management strategies. Given the significant toxicities of RAF and MEK inhibitors, along with the long potential duration of treatment, neuro-oncology providers should counsel patients carefully before initiating therapy and monitor them closely while undergoing treatment with RAF-targeted therapy.

Combination of BRAF and MEK inhibition in BRAF V600E mutant low-grade ganglioglioma

WHAT IS KNOWN AND OBJECTIVE

Post-surgical management of low grade gangliogliomas is controversial with paucity of data for the use of chemotherapy. BRAF mutations are present in a number of glioma subtypes and offer an opportunity for treatment with targeted therapy.

CASE SUMMARY

A 32-year-old man with an unresectable, BRAF V600E mutant, WHO grade 1 ganglioglioma is commenced on combination BRAF and MEK inhibition (vemurafenib and cobimetinib). Partial radiological and clinical response was noted after 13 weeks of treatment. Treatment complication with grade 2 skin and liver toxicity was resolved with dose interruption and reduction.

WHAT IS NEW AND CONCLUSION

Combination BRAF and MEK inhibition present a safe and feasible treatment strategy in unresectable BRAF V600E mutant low grade ganglioglioma.

Recurrent papillary craniopharyngioma with BRAF V600E mutation treated with dabrafenib: case report

The authors present the case of a man with a papillary craniopharyngioma, first diagnosed at 47 years of age, who experienced multiple recurrences. Review of the pathologic specimen from his first resection demonstrated the BRAF V600E mutation. With his most recent recurrence following previous surgery and radiotherapy, at 52 years of age, the decision was made to initiate treatment with the BRAF V600E inhibitor dabrafenib. Imaging following initiation of dabrafenib demonstrated reduction in tumor size. He remained on dabrafenib therapy for approximately 1 year and continued to demonstrate a good clinical result. At that time the decision was made to discontinue dabrafenib therapy and follow up with serial imaging. After more than 1 year of follow-up since stopping dabrafenib, the patient has continued to do well with no radiographic evidence of tumor progression and continues to be monitored with frequent interval imaging.

Prolonged Response Induced by Single Agent Vemurafenib in a BRAF V600E Spinal Ganglioglioma: A Case Report and Review of the Literature

Spinal ganglioglioma is a rare low-grade, slow-growing tumor of the central nervous system affecting mostly children and young adults. After surgery, some patients show tumor recurrence and/or malignant transformation. Gangliogliomas harbor molecular deficiencies such as mutations in the B-rapidly accelerated fibrosarcoma (BRAF) gene, resulting in activation of a downstream signaling pathway and cancer development. Vemurafenib is a BRAF inhibitor used to treat patients with BRAF V600E-mutated cancer. Although a few studies have reported the clinical responses in gangliogliomas, the sequence and duration of treatment have not been established. We describe a case of an adult with a progressive BRAF V600E mutant spinal cord ganglioglioma 9 years after surgery who was treated with vemurafenib. This treatment resulted in a partial response within 2 months, which was sustained for more than a year. The patient then decided to stop treatment because of side effects. Despite this decision, the tumor showed no sign of progression 21 months after treatment discontinuation. This is the first reported case of a response to vemurafenib in an adult with progressive spinal cord BRAF V600E-mutated ganglioglioma which was sustained after treatment discontinuation.

Dabrafenib Treatment in a Patient with an Epithelioid Glioblastoma and BRAF V600E Mutation

Novel therapeutic targets in malignant glioma patients are urgently needed. Point mutations of the v-Raf murine sarcoma viral oncogene homolog B (BRAF) gene occur predominantly in melanoma patients, but may also occur in gliomas. Thus, this is a target of great interest for this group of patients. In a nine-year-old male patient, an anaplastic astrocytoma in the left temporoparietal region was diagnosed histologically. After first- and second-line treatment, a malignant progression to a secondary glioblastoma was observed ten years after the initial diagnosis. Within the following seven years, all other conventional treatment options were exhausted. At this time point, recurrent tumor histology revealed an epithelioid glioblastoma, without a mutation in the isocitrate dehydrogenase gene (IDH wild-type). In order to identify a potential target for an experimental salvage therapy, mutational tumor analysis showed a BRAF V600E mutation. Consecutively, dabrafenib treatment was initiated. The patient remained clinically stable, and follow-up magnetic resonance images (MRI) were consistent with “Stable Disease” according to the Response Assessment in Neuro-Oncology Working Group (RANO) criteria for the following ten months until tumor progression was detected. The patient died 16 months after dabrafenib treatment initiation. Particularly in younger glioma patients as well as in patients with an epithelioid glioblastoma, screening for a V600E BRAF mutation is promising since, in these cases, targeted therapy with BRAF inhibitors seems to be a useful salvage treatment option.

BRAF V600E mutation is a significant prognosticator of the tumour regrowth rate in brainstem gangliogliomas

BRAF V600E mutations are progression factors in paediatric low-grade gliomas. Furthermore, a high percentage of paediatric brainstem gangliogliomas have BRAF V600E mutations. However, their clinical significance, including possible connections between the biomarkers and ganglioglioma's clinical features, especially a brainstem counterpart, is unclear. To identify potential molecular features predictive of brainstem ganglioglioma's clinical outcomes, a retrospective cohort of 28 World Health Organization (WHO) grade I brainstem gangliogliomas was analysed for BRAF V600E, IDH1 R132H, and IDH2 R172K mutations, TERT C228T/C250T promoter mutation, H3F3A K27M mutation and MGMT methylation. The volume of tumours was calculated accurately by using 3D Slicer software. The clinical data of these patients were retrospectively analysed. In tumours with BRAF V600E mutations, the tumour regrowth rate was significantly faster than that of the wild type group (p=0.001). Moreover, the BRAF V600E mutant group had shorter progression-free survival (PFS) compared with wild type (p=0.012). On multivariate analysis, no factor was found to be an independent prognostic factor; however, tumours with faster regrowth rates had a strong trend towards an increased risk for shorter PFS (HR=1.027, p=0.056). No statistical analysis could be performed to evaluate factors affecting overall survival (OS). These data suggest that BRAF V600E can predict the regrowth rate of brainstem gangliogliomas after microsurgery, and a BRAF V600E-targeted therapeutic may be a promising early intervention measure for patients who harbour BRAF V600E mutation after microsurgery.

Glioma Subclassifications and Their Clinical Significance

The impact of targeted therapies in glioma has been modest. All the therapies that have demonstrated a significant survival benefit for gliomas in Phase III trials, including radiation, chemotherapy (temozolomide and PCV [procarbazine, lomustine, vincristine]), and tumor-treating fields, are based on nonspecific targeting of proliferating cells. Recent advances in the molecular understanding of gliomas suggest some potential reasons for the failure of more targeted therapies in gliomas. Specifically, the histologic-based glioma classification is composed of multiple different molecular subtypes with distinct biology, natural history, and prognosis. As a result of these insights, the diagnosis and classification of gliomas have recently been updated by the World Health Organization. However, these changes and other novel observations regarding glioma biomarkers and subtypes highlight several clinical challenges. First, the field is faced with the difficulty of reinterpreting the results of prior studies and retrospective data using the new classifications to clarify prognostic assessments and treatment recommendations for patients. Second, the new classifications and insights require rethinking the design and stratification of future clinical trials. Last, these observations provide the essential framework for the development and testing of new specific targeted therapies for particular glioma subtypes. This review aims to summarize the current literature regarding glioma subclassifications and their clinical relevance in this evolving field.

Recent advances in subtyping tumors of the central nervous system using molecular data

INTRODUCTION

Primary brain tumors account for substantial morbidity and mortality. They often infiltrate the brain diffusely, continue growing, and cause adverse events, such as headaches, seizures, and neurological deficits. The classification of primary brain tumors, based for decades on histology, has been fundamentally changed by the World Health Organization in 2016 by incorporation of molecular data. Areas covered: Literature from glioblastomas, high- and low-grade astrocytic, oligodendroglial, glioneuronal and ependymal tumors from the last five years were reviewed. Results from comprehensive molecular profiling of neoplasms and impact of recent molecular subtyping on neuropathological diagnosis are presented. Expert commentary: The identification of frequent acquired mutations shows that adult and pediatric glioblastomas have divergent biology with differing prognoses. Astrocytoma and oligodendroglioma are more closely related than previously thought. Molecular profiling now enables the precise classification of most diffuse gliomas into three clinically and therapeutically different subtypes according to the presence or absence of IDH mutation and 1p/19q codeletion. New subgroups with different clinical outcomes and anatomic locations have emerged in ependymomas and pediatric embryonal tumors.