Xenotransplantation of pediatric low grade gliomas confirms the enrichment of BRAF V600E mutation and preservation of CDKN2A deletion in a novel orthotopic xenograft mouse model of progressive pleomorphic xanthoastrocytoma

The main pathogenetic mechanism of the development of pediatric low grade gliomas (pLGGs) is genetic aberrations in BRAF gene. This study is supported by the Independent Ethics Committee and approved by the Academic Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology, and Immunology. We analyzed the clinical and molecular characteristics of 69 patients with LGGs. Molecular genetic testing for BRAF V600E mutation was performed by allele-specific real-time PCR and Sanger sequencing. BRAF V600E mutation was detected in 15 (21.7%) patients with LGG. The majority of BRAF-mutated cases of LGGs had the midline location: OPG – 7, subcortical ganglia – 1, brainstem – 2. The 2-year PFS was much worse in patients with BRAF V600E compared to patients without this mutation – 30% and 66.2%, respectively. The median time to progression for patients with BRAF V600E mutation was 9.5 months compared to 3.1 years for patients without indicated substitution. 5 patients with BRAF V600E-mutated LGGs who experienced progression after the conventional treatment, received targeted therapy (BRAF-inhibitor-3, BRAF + MEK inhibitors – 2) with good response (complete response – 2, partial response – 3). BRAF V600E mutation contributes to poor outcome in patients with LGGs Targeted therapy could be effective in this cohort of patients.

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LG-46INFERIOR OUTCOME AND POOR RESPONSE TO CONVENTIONAL THERAPIES IN PEDIATRIC LOW-GRADE GLIOMAS HARBORING THE BRAF V600E MUTATION

Neuro-Oncology ◽

10.1093/neuonc/now075.46 ◽

2016 ◽

Vol 18 (suppl 3) ◽

pp. iii89.1-iii89

Author(s):

Alvaro Lassaletta ◽

Matthew Mistry ◽

Anthony Arnaldo ◽

Scott Ryall ◽

Ana Guerreiro-Stucklin ◽

...

Keyword(s):

Poor Response ◽

Braf V600e Mutation ◽

Braf V600e ◽

Low Grade ◽

Low Grade Gliomas

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Acquired ATRX Loss and ALT Phenotype Through Tumor Recurrences in a Case of Pleomorphic Xanthoastrocytoma Suggest Their Possible Roles in Tumor Progression

Journal of Neuropathology & Experimental Neurology ◽

10.1093/jnen/nlaa074 ◽

2020 ◽

Vol 79 (9) ◽

pp. 1011-1014

Author(s):

Pierre Dal Col ◽

Delphine Poncet ◽

Romain Rivoirard ◽

François Vassal ◽

Emilie Bernichon ◽

...

Keyword(s):

Young Adults ◽

Tumor Progression ◽

Pleomorphic Xanthoastrocytoma ◽

Braf V600e Mutation ◽

Braf V600e ◽

Tumor Evolution ◽

Molecular Alterations ◽

Astrocytic Glioma ◽

Alternative Lengthening ◽

Cdkn2a Deletion

Abstract Pleomorphic xanthoastrocytoma (PXA) is classified as an astrocytic glioma occurring most often in children or young adults. Molecular alterations in PXA are not fully known, especially those associated with tumor progression. We describe a patient with several relapses of a PXA. The tumor showed an acquired ATRX loss through tumor evolution. We tested alternative lengthening of telomeres (ALT) with the C-circle test. While the test was negative in the first tumor, a high circle activity was detected in the last relapse, suggesting an acquired ALT phenotype. Our data not only confirm previous findings of the possible occurrence of ATRX mutations in PXA but also suggest that this alteration is linked to PXA progression. In small biopsies, tumors with ATRX loss, without IDH or histone mutation, pathologists should consider the diagnosis of PXA, especially if associated with BRAF V600E mutation, CDKN2A deletion, and ALT.

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LGG-23. EXCELLENT CLINICAL / RADIOLOGICAL RESPONSE TO BRAF INHIBITION IN A YOUNG CHILD WITH IN-OPERABLE SUPRA-SELLAR PILOCYTIC ASTROCYTOMA

Neuro-Oncology ◽

10.1093/neuonc/noaa222.405 ◽

2020 ◽

Vol 22 (Supplement_3) ◽

pp. iii370-iii371

Author(s):

Stacy Chapman ◽

Demitre Serletis ◽

Colin Kazina ◽

Mubeen Rafay ◽

Sherry Krawitz ◽

...

Keyword(s):

Targeted Therapy ◽

Pilocytic Astrocytoma ◽

Clinical Symptoms ◽

Obstructive Hydrocephalus ◽

Braf V600e Mutation ◽

Braf V600e ◽

Low Grade ◽

Dramatic Improvement ◽

Chemotherapeutic Regimen ◽

Response To Chemotherapy

Abstract In-operable low grade gliomas (LGG) in the pediatric population continue to present a treatment dilemma. Due to the low-grade nature of these tumors, and variable response to chemotherapy / radiation, the choice of adjuvant treatment is difficult. Overall survival is directly related to the degree of surgical resection, adding complexity to these inoperable tumors. Current chemotherapeutic regimen for these inoperable tumors includes vincristine (VCR) and carboplatin (Carbo). With advancements in the molecular characterization of gliomas, the role of targeted therapy has come into question. We present a 2-year-old female with biopsy proven Pilocytic Astrocytoma (positive BRAF-V600E mutation) involving the hypothalamic/optic chiasm region. She presented with ataxic gait, bi-temporal hemianopia, obstructive hydrocephalus and central hypothyroidism, which progressed to altered consciousness, and right hemiparesis due to location/mass effect of the tumor. She was initially treated with chemotherapy (VCR/Carbo) but her tumor progressed at 6 weeks of treatment. As her tumor was positive for BRAF-V600E mutation, she was started on Dabrafenib monotherapy, resulting in dramatic improvement in her clinical symptoms (able to stand, improved vision), and a 60% reduction in tumor size at 3-months. At 6-months, follow up MRI showed slight increase in the solid portion of the tumor, with no clinical symptoms. We plan to add MEK inhibitor (Trametinib) and continue with Dabrafenib. Our experience and literature review suggests that LGG with BRAF-V600E mutations may benefit from upfront targeted therapy. Prospective clinical trials comparing the efficacy of BRAF inhibitors versus standard chemotherapy in LGG with BRAF mutations are urgently needed.

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HGG-02. ADOLESCENT AND YOUNG ADULT (AYA) GLIOMA WITH BRAF V600E-MUTANTATION

Neuro-Oncology ◽

10.1093/neuonc/noaa222.294 ◽

2020 ◽

Vol 22 (Supplement_3) ◽

pp. iii344-iii344

Author(s):

Yui Kimura ◽

Yukitomo Ishi ◽

Yuko Watanabe ◽

Yoshiko Nakano ◽

Shigeru Yamaguchi ◽

...

Keyword(s):

Braf Inhibitor ◽

Clinical Information ◽

Early Recurrence ◽

Pleomorphic Xanthoastrocytoma ◽

Adolescent And Young Adult ◽

Braf V600e ◽

Low Grade ◽

Diffuse Astrocytoma ◽

Genetic Features ◽

Epithelioid Glioblastoma

Abstract BACKGROUND Biological features of pediatric glioma differ significantly from those of adult glioma, and limited data are available on those of AYA patients. Here, we focused on AYA patients with glioma, especially those harboring BRAF V600E mutation, and investigated their clinical and genetic features. METHOD: We retrospectively analyzed AYA patients with brain tumors harboring BRAF V600E, who were treated in two hospitals in Japan. RESULTS Clinical information was available for 14 patients. The median age at diagnosis was 25 years (range: 15–38). Five patients were diagnosed with glioblastoma (GBM), including one epithelioid type. These patients were over 25. Although one patient with GBM died of the disease 6.9 years after initial diagnosis, the remaining patients were alive. Two patients were alive without recurrence at 38 and 51 months after the treatment. The patient with epithelioid glioblastoma experienced early recurrence. The remaining nine patients (64%) were diagnosed with low-grade glioma, including ganglioglioma, pilocytic astrocytoma, diffuse astrocytoma, oligodendroglioma, pleomorphic xanthoastrocytoma, and polymorphous low-grade neuroepithelial tumor of the young. No patients died of the disease, and four patients are alive without recurrence after initial operation without adjuvant treatment. Two patients are (epithelioid glioblastoma and ganglioglioma) currently undergoing treatment with a BRAF inhibitor for recurrent tumors. DISCUSSION Although the number of this study is limited, our study suggested that the prognosis of AYA patients with BRAF-V600E positive GBM may not be as dismal as that of children or adults.

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