Adult pilocytic astrocytoma in the molecular era: a comprehensive review

Predicting response to chemotherapy in brain tumor patients based on MRI features

Chemotherapy in brain tumors is tailored based on tumor type, grade, and molecular markers, which are crucial for predicting responses and survival outcomes. This review summarizes the role of chemotherapy in gliomas, glioneuronal and neuronal tumors, ependymomas, choroid plexus tumors, medulloblastomas, and meningiomas, discussing standard treatment protocols and recent developments in targeted therapies.Furthermore, the studies reporting the integration of MRI-based radiomics and deep learning models for predicting treatment outcomes are reviewed. Advances in MRI-based radiomics and deep learning models have significantly enhanced the prediction of chemotherapeutic benefits, survival prediction following chemotherapy, and differentiating tumor progression with psuedoprogression. These non-invasive techniques offer valuable insights into tumor characteristics and treatment responses, facilitating personalized therapeutic strategies. Further research is warranted to refine these models and expand their applicability across different brain tumor types.

Hypothalamic Hemangioma-like Pilocytic Astrocytoma in an Adult Patient: A Systematic Review with a Focus on Differential Diagnosis and Neurological Presentation

Background: Pilocytic astrocytoma (PCA) are commonly observed as slow-growing noncancerous brain tumors in pediatric populations, but they can also occur in adults, albeit rarely. When located in diencephalic regions, particularly in the hypothalamus, they present unique diagnostic and management challenges due to their rarity and overlapping clinical and radiological features with other intracranial pathologies. This systematic review aims to provide a comprehensive understanding of hypothalamic PCA in adults, focusing on their differential diagnosis, neurological presentation, diagnostic modalities, treatment strategies. A case illustration is also described in order to better underline all the difficulties related to the diagnostic process. Material and methods: A systematic literature search was conducted in the PubMed/MEDLINE, Embase, and Scopus databases up to November 2023 to identify studies. Results: The systematic literature search identified a total of 214 articles. Following screening by title and abstract and full-text review, 12 studies were deemed eligible and are included here. Conclusions: Adult-onset PCA in diencephalic regions pose diagnostic challenges due to their rarity and overlapping features with other intracranial lesions. Advanced imaging techniques play a crucial role in diagnosis, while surgery remains the cornerstone of treatment. Multidisciplinary collaboration is essential for the optimal management and long-term follow-up of these patients.

MEK Inhibition in a Pilocytic Astrocytoma With a Rare KRAS Q61R Mutation in a Young Adult Patient: A Case Report

This case illustrates the utility and impact of molecular testing and molecular tumor board discussion in the management of AYA patients with brain tumors.

A review of natural products and small-molecule therapeutics acting on central nervous system malignancies: Approaches for drug development, targeting pathways, clinical trials, and challenges

In 2021, the World Health Organization released the fifth edition of the central nervous system (CNS) tumor classification. This classification uses histopathology and molecular pathogenesis to group tumors into more biologically and molecularly defined entities. The prognosis of brain cancer, particularly malignant tumors, has remained poor worldwide, approximately 308,102 new cases of brain and other CNS tumors were diagnosed in the year 2020, with an estimated 251,329 deaths. The cost and time-consuming nature of studies to find new anticancer agents makes it necessary to have well-designed studies. In the present study, the pathways that can be targeted for drug development are discussed in detail. Some of the important cellular origins, signaling, and pathways involved in the efficacy of bioactive molecules against CNS tumorigenesis or progression, as well as prognosis and common approaches for treatment of different types of brain tumors, are reviewed. Moreover, different study tools, including cell lines, in vitro, in vivo, and clinical trial challenges, are discussed. In addition, in this article, natural products as one of the most important sources for finding new chemotherapeutics were reviewed and over 700 reported molecules with efficacy against CNS cancer cells are gathered and classified according to their structure. Based on the clinical trials that have been registered, very few of these natural or semi-synthetic derivatives have been studied in humans. The review can help researchers understand the involved mechanisms and design new goal-oriented studies for drug development against CNS malignancies.

Pilocytic astrocytoma: The paradigmatic entity in low‑grade gliomas (Review)

Among low-grade gliomas, representing 10-20% of all primary brain tumours, the paradigmatic entity is constituted by pilocytic astrocytoma (PA), considered a grade 1 tumour by the World Health Organization. Generally, this tumour requires surgical treatment with an infrequent progression towards malignant gliomas. The present review focuses on clinicopathological characteristics, and reports imaging, neurosurgical and molecular features using a multidisciplinary approach. Macroscopically, PA is a slow-growing soft grey tissue, characteristically presenting in association with a cyst and forming a small mural nodule, typically located in the cerebellum, but sometimes occurring in the spinal cord, basal ganglia or cerebral hemisphere. Microscopically, it may appear as densely fibrillated areas composed of elongated pilocytic cells with bipolar 'hairlike' processes or densely fibrillated areas composed of elongated pilocytic cells with Rosenthal fibres alternating with loosely fibrillated areas with a varied degree of myxoid component. A wide range of molecular alterations have been encountered in PA, mostly affecting the MAPK signalling pathway. In detail, the most frequent alteration is a rearrangement of the BRAF gene, although other alterations include neurofibromatosis type-1 mutations, BRAFV600E mutations, KRAS mutations, fibroblast growth factor receptor-1 mutations of fusions, neurotrophic receptor tyrosine kinase family receptor tyrosine kinase fusions and RAF1 gene fusions. The gold standard of PA treatment is surgical excision with complete margin resection, achieving minimal neurological damage. Conventional radiotherapy is not required; the more appropriate treatment appears to be serial follow-up. Chemotherapy should only be applied in younger children to avoid the risk of long-term growth and developmental issues associated with radiation. Finally, if PA recurs, a new surgical approach should be performed. At present, novel therapy involving agents targeting MAPK signalling pathway dysregulation is in development, defining BRAF and MEK inhibitors as target therapeutical agents.

Rare vermian pilocytic astrocytoma with recurrent spontaneous hemorrhage in the elderly: A case report and review of literature

Background

Pilocytic astrocytoma (PA) is a benign glial tumor predominately seen in pediatrics and early adolescence with associated overall good outcomes. Very few cases of elderly PA have been reported in the literature, and they are known to display unique anatomic, histologic, and genetic peculiarities distinct from pediatric disease. We report a rare case of vermian PA in an octogenarian with recurrent spontaneous intratumoral hemorrhage as a presenting symptom. Furthermore, a review of the literature on the peculiarities of PA in the elderly will be discussed.

Case Description

An 81-year-old woman presented with features suggestive of repeated posterior fossa hemorrhages characterized by headaches, diplopia, and alteration in sensorium occurring about 5 months apart. Brain neuroimaging showed a cerebellar vermian tumor with features suggestive of repeated intratumoral bleeding. She had an initial ventriculoperitoneal shunting for acute hydrocephalus and subsequently had a suboccipital craniotomy and subtotal tumor excision due to morbid adherence to the brainstem. The histologic diagnosis was PA with Ki-67 <1% and negative for isocitrate dehydrogenase-1. There was a slow but progressive clinical improvement, and she has remained symptom-free for 4 years on follow-up.

Conclusion

PA in the elderly is a rare disease with distinct histologic and genetic peculiarities. This case review showed one of the oldest cases of cerebellar vermian PA presenting with recurrent spontaneous intratumoral hemorrhage, an extremely rare occurrence in benign glioma. Although complete surgical excision is recommended, partial resection is advocated for morbidly adherent tumors. Overall prognosis is worse in elderly PA.

Pediatric-Like Brain Tumors in Adults

Pediatric brain tumors are different to those found in adults in pathological type, anatomical site, molecular signature, and probable tumor drivers. Although these tumors usually occur in childhood, they also rarely present in adult patients, either as a de novo diagnosis or as a delayed recurrence of a pediatric tumor in the setting of a patient that has transitioned into adult services.Due to the rarity of pediatric-like tumors in adults, the literature on these tumor types in adults is often limited to small case series, and treatment decisions are often based on the management plans taken from pediatric studies. However, the biology of these tumors is often different from the same tumors found in children. Likewise, adult patients are often unable to tolerate the side effects of the aggressive treatments used in children-for which there is little or no evidence of efficacy in adults. In this chapter, we review the literature and summarize the clinical, pathological, molecular profile, and response to treatment for the following pediatric tumor types-medulloblastoma, ependymoma, craniopharyngioma, pilocytic astrocytoma, subependymal giant cell astrocytoma, germ cell tumors, choroid plexus tumors, midline glioma, and pleomorphic xanthoastrocytoma-with emphasis on the differences to the adult population.

Brain Tumors in Adolescents and Young Adults: A Review

Brain tumors account for the majority of cancer-related deaths in adolescents and young adults (AYAs), defined as individuals aged 15 to 39. AYAs constitute a distinct population in which both pediatric- and adult-type central nervous system (CNS) tumors can be observed. Clinical manifestations vary depending on tumor location and often include headaches, seizures, focal neurological deficits, and signs of increased intracranial pressure. With the publication of the updated World Health Organization CNS tumor classification in 2021, diagnoses have been redefined to emphasize key molecular alterations. Gliomas represent the majority of malignant brain tumors in this age group. Glioneuronal and neuronal tumors are associated with longstanding refractory epilepsy. The classification of ependymomas and medulloblastomas has been refined, enabling better identification of low-risk tumors that could benefit from treatment de-escalation strategies. Owing to their midline location, germ cell tumors often present with oculomotor and visual alterations as well as endocrinopathies. The management of CNS tumors in AYA is often extrapolated from pediatric and adult guidelines, and generally consists of a combination of surgical resection, radiation therapy, and systemic therapy. Ongoing research is investigating multiple agents targeting molecular alterations, including isocitrate dehydrogenase inhibitors, SHH pathway inhibitors, and BRAF inhibitors. AYA patients with CNS tumors should be managed by multidisciplinary teams and counselled regarding fertility preservation, psychosocial comorbidities, and risks of long-term comorbidities. There is a need for further efforts to design clinical trials targeting CNS tumors in the AYA population.

Comparison of the clinical features and treatment outcomes of pilocytic astrocytoma in pediatric and adult patients

PURPOSE

Pilocytic astrocytoma is a slow-growing tumor that predominantly develops in children, but has a broad age spectrum. A notable characteristic of pilocytic astrocytoma is that the tumor arises in diverse locations and the clinical course is not always benign. Therefore, it is necessary to elucidate the clinical spectrum of the disease and analyze the relevant prognostic factors.

METHODS

Demographic and treatment-related factors were retrospectively reviewed in a cohort of 254 patients with histologically confirmed pilocytic astrocytoma. Clinical features were compared between the pediatric group (N = 208; age < 18 years) and the adult group (N = 46; age ≥ 18 years). Cox regression analysis was performed to identify relevant prognostic factors.

RESULTS

There was no difference in progression-free survival (PFS) between the pediatric and adult groups (p = 0.36); however, patients under 8 years of age exhibited worse PFS (p < 0.01). Leptomeningeal seeding at diagnosis and pilomyxoid histology was observed only in pediatric patients. In the pediatric group, nine patients experienced recurrence after complete resection. Increasing age (hazard ratio (HR) = 0.89, p < 0.01) and adjuvant therapy (HR = 0.32, p < 0.01) were protective factors against tumor progression. In the adult group, no progression occurred after complete resection. Age and adjuvant therapy were not significant factors in the adult group.

CONCLUSION

Pilocytic astrocytoma presents with a diverse clinical spectrum. Complete resection is of utmost importance, and appropriate adjuvant treatment is recommended if complete resection cannot be achieved. Children with younger age are associated with more aggressive tumors, and recurrence may occur even after complete resection.

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.

Dabrafenib Plus Trametinib: An Impressive Response in an Adult Patient With BRAF V600E-Mutated and Isocitrate Dehydrogenase (IDH) Wild-Type Glioma

Key molecular alterations found in the diagnosis and prognosis of brain tumours have been revealed by the latest advances in transcriptomic and genome-wide analysis. In-depth studies revealed that alterations of the V-Raf murine sarcoma viral oncogene homolog B (BRAF) could be shared by different brain tumour types. The identification of BRAF p.V600E mutations in gliomas is nowadays of more importance regarding the development of BRAF-targeted inhibitors.

This report presents the case of a 37-year-old female with a voluminous expansive neoplastic lesion, extending from the lenticulocapsular region to the medial aspect of the temporal lobe on the left. Pathological examination revealed an astrocytic neoplasm without high-grade histological features in small biopsy fragments. The molecular study revealed the presence of a mutation in the BRAF V600E gene and CDKN2A/2B homozygous deletion. The lesion was partially removed and irradiated. The patient has been on treatment with dabrafenib plus trametinib for 10 months. In addition to reasonable tolerance, she obtained an impressive tumour reduction, which was manifested in the complete resolution of neurological deficits and in the full acquisition of autonomy.

The remarkable results reported in this clinical case justify the pressing need to identify new therapeutic targets in gliomas in the current era of precision medicine.

EANO - EURACAN - SNO Guidelines on circumscribed astrocytic gliomas, glioneuronal, and neuronal tumors

In the new WHO 2021 Classification of CNS Tumors the chapter "Circumscribed astrocytic gliomas, glioneuronal and neuronal tumors" encompasses several different rare tumor entities, which occur more frequently in children, adolescents, and young adults. The Task Force has reviewed the evidence of diagnostic and therapeutic interventions, which is low particularly for adult patients, and draw recommendations accordingly. Tumor diagnosis, based on WHO 2021, is primarily performed using conventional histological techniques; however, a molecular workup is important for differential diagnosis, in particular, DNA methylation profiling for the definitive classification of histologically unresolved cases. Molecular factors are increasing of prognostic and predictive importance. MRI finding are non-specific, but for some tumors are characteristic and suggestive. Gross total resection, when feasible, is the most important treatment in terms of prolonging survival and achieving long-term seizure control. Conformal radiotherapy should be considered in grade 3 and incompletely resected grade 2 tumors. In recurrent tumors reoperation and radiotherapy, including stereotactic radiotherapy, can be useful. Targeted therapies may be used in selected patients: BRAF and MEK inhibitors in pilocytic astrocytomas, pleomorphic xanthoastrocytomas, and gangliogliomas when BRAF altered, and mTOR inhibitor everolimus in subependymal giant cells astrocytomas. Sequencing to identify molecular targets is advocated for diagnostic clarification and to direct potential targeted therapies.

Pilocytic astrocytoma of the optic nerve with intracystic hemorrhage in an adult: illustrative case

BACKGROUND

Optic pathway gliomas are uncommon, accounting for 3–5% of childhood brain tumors, and are mostly classified as pilocytic astrocytomas (PAs). PAs of the optic nerve are particularly rare in adults.

OBSERVATIONS

The authors presented the case of PA of the left optic nerve in a 49-year-old woman along with detailed pathological and molecular analyses and sequential magnetic resonance imaging. The tumor had progressed during 5 years of follow-up along with cyst formation and intracystic hemorrhage; it had a thick capsule and contained xanthochromic fluid. The boundary between tumor and optic nerve was unclear. B-type Raf kinase (BRAF) V600E point mutations or translocations, IDH1-R132H mutations, loss of alpha-thalassemia/mental retardation X-linked, and 1p/19q codeletion were negative.

LESSONS

BRAF alterations in pediatric PAs of the optic nerve are less frequent than those observed in PAs in other lesions; the same molecular pattern was observed in the adult case, without changes in BRAF. Surgical management should be indicated only in cases with severely impaired vision or disfigurement because there is no clear border between the tumor and optic nerve. Further discussion is needed to optimize the treatment for adult optic pathway gliomas, including radiotherapy, chemotherapy, and molecular-targeted therapies, in addition to surgical intervention.

Insight about the characteristics and surgical resectability of adult pilocytic astrocytoma: tertiary center experience

Aim: Adult pilocytic astrocytoma is a rare tumor. We aim to contribute to understanding its clinical course and prognosis. Patients & methods: We searched our database for patients older than 18 years with pathology-proven pilocytic astrocytoma. Patients' clinical data were analyzed. Results: Fifteen patients were identified. The median age at diagnosis was 25 years (range: 18-56). Tumors were supratentorial in 47%. Gross-total and near-total resections were achieved in 40%, and sub-total resection in 47%. One (7%) recurrence and no mortality were encountered during a median follow-up of 11 months (range: 1-76). Conclusion: Pilocytic astrocytoma behaves differently in adults compared with pediatrics. It tends to arise in surgically challenging areas where the extent of resection may be limited. Total resection should be the main therapy whenever feasible. The survival rates are good, and recurrence is low.

EGFR Amplification Is a Phenomenon of IDH Wildtype and TERT Mutated High-Grade Glioma: An Integrated Analysis Using Fluorescence In Situ Hybridization and DNA Methylome Profiling

Gliomas are the most common intrinsic brain tumors in adults, and in accordance with their clinical behavior and patients’ outcome, they are graded by the World Health Organization (WHO) classification of brain tumors. One very interesting candidate for targeted tumor therapy may be epidermal growth factor receptor (EGFR) amplification. Here, we performed an integrated comparative analysis of EGFR amplification in 34 glioma samples using standard fluorescence in situ hybridization (FISH) and Illumina EPIC Infinium Methylation Bead Chip and correlated results with molecular glioma hallmarks. We found that the EPIC analysis showed the same power of detecting EGFR amplification compared with FISH. EGFR amplification was detectable in high-grade gliomas (25%). Moreover, EGFR amplification was found to be present solely in IDH wildtype gliomas (26%) and TERT mutated gliomas (27%), occurring independently of MGMT promoter methylation status and being mutually exclusive with 1p/19q codeletion (LOH). In summary, EPIC Bead Chip analysis is a reliable tool for detecting EGFR amplification and is comparable with the standard method FISH. EGFR amplification is a phenomenon of IDH wildtype TERT mutated high-grade gliomas.

A fully automatic multiparametric radiomics model for differentiation of adult pilocytic astrocytomas from glioblastomas

OBJECTIVES

To develop a fully automatic radiomics model to differentiate adult pilocytic astrocytomas (PA) from high-grade gliomas (HGGs).

METHODS

This retrospective study included 302 adult patients with PA (n = 62) or HGG (n = 240). The patients were randomly divided into training (n = 211) and test (n = 91) sets. Clinical data were obtained, and radiomic features (n = 372) were extracted from multiparametric MRI with automatic tumour segmentation. After feature selection with F-score, a Light Gradient Boosting Machine classifier with subsampling was trained to develop three models: (1) clinical model, (2) radiomics model, and (3) combined clinical and radiomics model. Human performance was also assessed. The performance of the classifier was validated in the test set. SHapley Additive exPlanations (SHAP) was applied to explore the interpretability of the model.

RESULTS

A total of 15 radiomic features were selected. In the test set, the combined clinical and radiomics model (area under the curve [AUC], 0.93) showed a significantly higher performance than the clinical model (AUC, 0.79, p = 0.037) and had a similar performance to the radiomics model (AUC, 0.92, p = 0.828). The combined clinical and radiomics model also showed a significantly higher performance than humans (AUC, 0.76-0.81, p < 0.05). The model explanation by SHAP suggested that lower intratumoural heterogeneity from T2-weighted images was highly associated with PA diagnosis.

CONCLUSIONS

The fully automatic combined clinical and radiomics model may be helpful for differentiating adult PAs from HGGs.

KEY POINTS

• Differentiating adult PAs from HGGs is challenging because PAs may manifest a large spectrum of imaging presentations, often including aggressive imaging features. • The fully automatic combined clinical and radiomics model showed a significantly higher performance than the clinical model or humans. • The model explanation by SHAP suggested that second-order features from T2-weighted imaging were important in diagnosis and might reflect the underlying pathophysiology that PAs have lesser tissue heterogeneity than HGGs.

Prognostic Factors Independently Associated With Improved Progression-Free Survival After Surgical Resection in Patients With Spinal Cord Astrocytomas: An Institutional Case Series

BACKGROUND

Spinal astrocytomas are rare tumors in which the extent of resection and adjuvant therapy remain controversial. A number of new molecular markers are used, but their utility in spinal cord tumors remains unclear.

OBJECTIVE

To determine prognostic indicators of progression-free survival (PFS) in patients with spinal astrocytomas.

METHODS

A retrospective chart review identified all patients managed at a single institution for spinal cord astrocytomas between 1999 and 2019. Data collected included baseline demographics, presenting signs and symptoms, tumor size, operative outcomes, and adjuvant treatment. Pathological data including histopathological grade, proliferative index, and molecular profile were collected. Duration of follow-up, presence of tumor progression, and status at last follow-up were documented. Univariate and multivariate analyses were performed to determine predictors of PFS.

RESULTS

Seventy-five patients were included in our study with an average age of 42 ± 17 yr. The thoracic spine was the most commonly involved spinal segment (50 patients), and most patients had grade I or grade II tumors (50 patients). On univariate analysis, gross total resection (GTR), lower tumor grade, and low Ki-67 index were associated with lower tumor progression (P-values .01, .04, and .00013, respectively). On multivariate Cox regression analysis, GTR, adjuvant chemotherapy and radiation, and low Ki-67 index were independent predictors of PFS (P-values .009, .011, and .031, respectively).

CONCLUSION

In spinal astrocytomas, GTR, adjuvant therapy, and low Ki-67 are independently associated with improved PFS. These data may help guide management of these tumors and provide important prognosticating information.