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Background: Dihydroxy‐6‐[18F]fluoro‐L‐phenylalanine (18F‐FDOPA) positron emission tomography (PET) is a valuable tool for managing high‐grade gliomas (HGGs), but there is a lack of literature on its relationship with glioma subtypes since the 2021 reclassification of brain tumors. There is also debate surrounding the mechanism of 18F‐FDOPA uptake, particularly after chemoradiation therapy. This study aimed to investigate the correlation between 18F‐FDOPA uptake and histomolecular characteristics, particularly L‐amino acid transporter 1 (LAT1) expression, in recurrent gliomas, and examine their impact on survival in HGGs. Methods: Thirty‐nine patients with recurrent HGGs (14 isocitrate dehydrogenase [IDH]‐mutant, 25 IDH‐wildtype) who underwent a brain 18F‐FDOPA PET/computed tomography (CT) or PET/magnetic resonance imaging (MRI) followed by surgical resection of the 18F‐FDOPA‐avid lesion within 6 months, were retrospectively reviewed. PET results were compared with histological examination and for SCL7A5/LAT1 immunostaining. The study also examined the relationship between PET parameters, LAT1 expression, and survival outcomes. Results: Astrocytoma IDH‐mutant G4 had higher 18F‐FDOPA uptake than glioblastoma IDH‐wildtype G4 (maximum tumor‐to‐normal brain ratio [TBRmax] 5 [3.4–9] vs. 3.8 [2.8–5.9], p = 0.02). IDH‐mutant gliomas had higher LAT1 expression than IDH‐wildtype gliomas (100 [14–273] vs. 15.5 [0–137], p < 0.05) as well as higher TBRmax (5 [2.4–9] vs. 3.8 [2.8–6], p < 0.05). In survival analysis, LAT1 score >100 was a predictor for longer progression‐free survival in IDH‐mutant HGGs. Conclusions: To our knowledge, our study is the first to suggest a link between LAT1 expression and IDH mutation status. We showed that higher TBRmax was associated with higher LAT1 expression and IDH mutation status. Further studies are needed to better understand the mechanisms underlying amino acid PET tracers uptake, especially in the post‐radiation and chemotherapy settings. [ABSTRACT FROM AUTHOR]

Background: Glioblastoma (GBM) is the most common and aggressive primary malignant brain tumor. Leptomeningeal spread (LMS) is a severe complication of GBM, raising diagnostic and therapeutic challenges in clinical routine. Methods: We performed a review of the literature focused on LMS in GBM. MEDLINE and EMBASE databases were queried from 1989 to 2019 for articles describing diagnosis and therapeutic options in GBM LMS, as well as risk factors and pathogenic mechanisms. Results: We retrieved 155 articles, including retrospective series, case reports, and early phase clinical trials, as well as preclinical studies. These articles confirmed that LMS in GBM remains (a) a diagnostic challenge with cytological proof of LMS obtained in only 35% of cases and (b) a therapeutic challenge with a median overall survival below 2 months with best supportive care alone. For patients faced with suggestive clinical symptoms, whole neuroaxis magnetic resonance imaging and cerebrospinal fluid analysis are both recommended. Liquid biopsies are under investigation and may help prompt a reliable diagnosis. Based on the literature, a multimodal and personalized therapeutic approach of LMS, including surgery, radiotherapy, systemic cytotoxic chemotherapy, and intrathecal chemotherapies, may provide benefits to selected patients. Interestingly, molecular targeted therapies appear promising in case of actionable molecular target and should be considered. Conclusion: As the prognosis of glioblastoma is improving over time, LMS becomes a more common complication. Our review highlights the need for translational studies and clinical trials dedicated to this challenging condition in order to improve diagnostic and therapeutic strategies. Implications for Practice: This review summarizes the diagnostic tools and applied treatments for leptomeningeal spread, a complication of glioblastoma, as well as their outcomes. The importance of exhaustive molecular testing for molecular targeted therapies is discussed. New diagnostic and therapeutic strategies are outlined, and the need for translational studies and clinical trials dedicated to this challenging condition is highlighted. This article reviews diagnostic tools and applied treatments for leptomeningeal spread, a severe complication of glioblastoma raising diagnostic and therapeutic challenges in clinical routine. The importance of molecular testing and its importance in the setting of molecular targeted therapies is also reviewed. [ABSTRACT FROM AUTHOR]

Background: Astroblastoma (ABM) is a rare glial brain tumor. Recurrent meningioma 1 (MN1) alterations have been recently identified in most pediatric cases. Adolescent and adult cases, however, remain molecularly poorly defined. Materials and Methods: We performed clinical and molecular characterization of a retrospective cohort of 14 adult and 1 adolescent ABM. Results: Strikingly, we found that MN1 fusions are a rare event in this age group (1/15). Using methylation profiling and targeted sequencing, most cases were reclassified as either pleomorphic xanthoastrocytomas (PXA)‐like or high‐grade glioma (HGG)‐like. PXA‐like ABM show BRAF mutation (6/7 with V600E mutation and 1/7 with G466E mutation) and CD34 expression. Conversely, HGG‐like ABM harbored specific alterations of diffuse midline glioma (2/5) or glioblastoma (GBM; 3/5). These latter patients showed an unfavorable clinical course with significantly shorter overall survival (p =.021). Mitogen‐activated protein kinase pathway alterations (including FGFR fusion, BRAF and NF1 mutations) were present in 10 of 15 patients and overrepresented in the HGG‐like group (3/5) compared with previously reported prevalence of these alterations in GBM and diffuse midline glioma. Conclusion: We suggest that gliomas with astroblastic features include a variety of molecularly sharply defined entities. Adult ABM harboring molecular features of PXA and HGG should be reclassified. Central nervous system high‐grade neuroepithelial tumors with MN1 alterations and histology of ABM appear to be uncommon in adults. Astroblastic morphology in adults should thus prompt thorough molecular investigation aiming at a clear histomolecular diagnosis and identifying actionable drug targets, especially in the mitogen‐activated protein kinase pathway. Implications for Practice: Astroblastoma (ABM) remains a poorly defined and controversial entity. Although meningioma 1 alterations seem to define a large subset of pediatric cases, adult cases remain molecularly poorly defined. This comprehensive molecular characterization of 1 adolescent and 14 adult ABM revealed that adult ABM histology comprises several molecularly defined entities, which explains clinical diversity and identifies actionable targets. Namely, pleomorphic xanthoastrocytoma‐like ABM cases show a favorable prognosis whereas high‐grade glioma (glioblastoma and diffuse midline gliome)‐like ABM show significantly worse clinical courses. These results call for in‐depth molecular analysis of adult gliomas with astroblastic features for diagnostic and therapeutic purposes. Astroblastoma is a rare central nervous system tumor. This article reports on the common clinical and molecular features of astroblastoma in a cohort of 14 adults and one adolescent. [ABSTRACT FROM AUTHOR]

Adult glioblastomas, IDH‐wildtype represent a heterogeneous group of diseases. They are resistant to conventional treatment by concomitant radiochemotherapy and carry a dismal prognosis. The discovery of oncogenic gene fusions in these tumors has led to prospective targeted treatments, but identification of these rare alterations in practice is challenging. Here, we report a series of 30 adult diffuse gliomas with an in frame FGFR3‐TACC3 oncogenic fusion (n = 27 WHO grade IV and n = 3 WHO grade II) as well as their histological and molecular features. We observed recurrent morphological features (monomorphous ovoid nuclei, nuclear palisading and thin parallel cytoplasmic processes, endocrinoid network of thin capillaries) associated with frequent microcalcifications and desmoplasia. We report a constant immunoreactivity for FGFR3, which is a valuable method for screening for the FGFR3‐TACC3 fusion with 100% sensitivity and 92% specificity. We confirmed the associated molecular features (typical genetic alterations of glioblastoma, except the absence of EGFR amplification, and an increased frequency of CDK4 and MDM2 amplifications). FGFR3 immunopositivity is a valuable tool to identify gliomas that are likely to harbor the FGFR3‐TACC3 fusion for inclusion in targeted therapeutic trials. [ABSTRACT FROM AUTHOR]

Chordoid glioma (ChG) is a characteristic, slow growing, and well-circumscribed diencephalic tumor, whose mutational landscape is unknown. Here we report the analysis of 16 ChG by whole-exome and RNA-sequencing. We found that 15 ChG harbor the same PRKCAD463H mutation. PRKCA encodes the Protein kinase C (PKC) isozyme alpha (PKCα) and is mutated in a wide range of human cancers. However the hot spot PRKCAD463H mutation was not described in other tumors. PRKCAD463H is strongly associated with the activation of protein translation initiation (EIF2) pathway. PKCαD463H mRNA levels are more abundant than wildtype PKCα transcripts, while PKCαD463H is less stable than the PCKαWT protein. Compared to PCKαWT, the PKCαD463H protein is depleted from the cell membrane. The PKCαD463H mutant enhances proliferation of astrocytes and tanycytes, the cells of origin of ChG. In conclusion, our study identifies the hallmark mutation for chordoid gliomas and provides mechanistic insights on ChG oncogenesis. [ABSTRACT FROM AUTHOR]

The integrated diagnosis of anaplastic oligodendroglioma, IDH mutant and 1p/19q co-deleted, grade III (O3id) is a histomolecular entity that WHO 2016 classification distinguished from other diffuse gliomas by specific molecular alterations. In contrast, its cell portrait is less well known. The present study is focused on intertumor and intratumor, cell lineage-oriented, heterogeneity in O3id. Based on pathological, transcriptomic and immunophenotypic studies, a novel subgroup of newly diagnosed O3id overexpressing neuronal intermediate progenitor (NIP) genes was identified. This NIP overexpression pattern in O3id is associated with: (i) morphological and immunohistochemical similarities with embryonic subventricular zone, (ii) proliferating tumor cell subpopulation with NIP features including expression of INSM1 and no expression of SOX9, (iii) mutations in critical genes involved in NIP biology and, (iv) increased tumor necrosis. Interestingly, NIP tumor cell subpopulation increases in O3id recurrence compared with paired newly diagnosed tumors. Our results, validated in an independent cohort, emphasize intertumor and intratumor heterogeneity in O3id and identified a tumor cell subpopulation exhibiting NIP characteristics that is potentially critical in oncogenesis of O3id. A better understanding of spatial and temporal intratumor cell heterogeneity in O3id will open new therapeutic avenues overcoming resistance to current antitumor treatments. [ABSTRACT FROM AUTHOR]

Simple Summary: Brain cancers, such as gliomas, are very difficult to detect because of their localization and late onset of symptoms. Here, we have developed a novel cancer detection method based on plasma denaturation profiles obtained by a non-conventional use of Differential Scanning Fluorimetry. Using blood samples from glioma patients and healthy controls, we show that their denaturation profiles can be automatically distinguished with the help of machine learning algorithms with 92% accuracy. This promising approach can now be extended to other types of cancers and could become a powerful pan-cancer diagnostic and monitoring tool requiring only a simple blood test. Glioblastoma is the most frequent and aggressive primary brain tumor. Its diagnosis is based on resection or biopsy that could be especially difficult and dangerous in the case of deep location or patient comorbidities. Monitoring disease evolution and progression also requires repeated biopsies that are often not feasible. Therefore, there is an urgent need to develop biomarkers to diagnose and follow glioblastoma evolution in a minimally invasive way. In the present study, we described a novel cancer detection method based on plasma denaturation profiles obtained by a non-conventional use of differential scanning fluorimetry. Using blood samples from 84 glioma patients and 63 healthy controls, we showed that their denaturation profiles can be automatically distinguished with the help of machine learning algorithms with 92% accuracy. Proposed high throughput workflow can be applied to any type of cancer and could become a powerful pan-cancer diagnostic and monitoring tool requiring only a simple blood test. [ABSTRACT FROM AUTHOR]

All cancer cells need to maintain functional telomeres to sustain continuous cell division and proliferation. In human diffuse gliomas, functional telomeres are maintained due either to reactivation of telomerase expression, the main pathway in most cancer types, or to activation of a mechanism called the alternative lengthening of telomeres (ALT). The presence of IDH1/2 mutations (IDH-mutant) together with loss of ATRX expression (ATRX-lost) are frequently associated with ALT in diffuse gliomas. However, detection of ALT, and a fortiori its quantification, are rarely, if ever, measured in neuropathology laboratories. We measured the level of ALT activity using the previously described quantitative "C-circle" assay and analyzed it in a well characterized cohort of 104 IDH-mutant and ATRX-lost adult diffuse gliomas. We report that in IDH-mutant ATRX-lost anaplastic astrocytomas, the intensity of ALT was inversely correlated with age (p < 0.001), the younger the patient, the higher the intensity of ALT. Strikingly, glioblastomas having progressed from anaplastic astrocytomas did not exhibit this correlation. ALT activity level in the tumor did not depend on telomere length in healthy tissue cells from the same patient. In summary, we have uncovered the existence, in anaplastic astrocytomas but not in glioblastomas with the same IDH and ATRX mutations, of a correlation between patient age and the level of activity of ALT, a telomerase-independent pathway of telomere maintenance. [ABSTRACT FROM AUTHOR]

Novel effective treatments are needed for recurrent IDH mutant high-grade gliomas (IDHm HGGs). The aim of the multicentric, single-arm, phase II REVOLUMAB trial (NCT03925246) was to assess the efficacy and safety of the anti-PD1 Nivolumab in patients with recurrent IDHm HGGs. Adult patients with IDHm WHO grade 3–4 gliomas recurring after radiotherapy and ≥ 1 line of alkylating chemotherapy were treated with intravenous Nivolumab until end of treatment (12 months), progression, unacceptable toxicity, or death. The primary endpoint was the 24-week progression-free survival rate (24w-PFS) according to RANO criteria. From July 2019 to June 2020, 39 patients with recurrent IDHm HGGs (twenty-one grade 3, thirteen grade 4, five grade 2 with radiological evidence of anaplastic transformation; 39% 1p/19q codeleted) were enrolled. Median time since diagnosis was 5.7 years, and the median number of previous systemic treatments was two. The 24w-PFS was 28.2% (11/39, CI95% 15–44.9%). Median PFS and OS were 1.84 (CI95% 1.81–5.89) and 14.7 months (CI95% 9.18-NR), respectively. Four patients (10.3%) achieved partial response according to RANO criteria. There were no significant differences in clinical or histomolecular features between responders and non-responders. The safety profile of Nivolumab was consistent with prior studies. We report the results of the first trial of immune checkpoint inhibitors in IDHm gliomas. Nivolumab failed to achieve its primary endpoint. However, treatment was well tolerated, and long-lasting responses were observed in a subset of patients, supporting further evaluation in combination with other agents (e.g. IDH inhibitors). • REVOLUMAB is the first phase II trial of checkpoint inhibitors in r/r IDHmut gliomas. • The trial did not meet its primary endpoint on the 24-week progression-free survival. • Nivolumab was well tolerated in patients with r/r IDHmut gliomas. • Long-lasting partial responses were observed in a subset of patients. [ABSTRACT FROM AUTHOR]