BRAFv600e mutated gliomas: From biology to radiology and treatments.

Abstract

e13552 Background: BRAF V600E mutation is encountered in brain tumor, mostly low grade pediatric diffuse glioma (LGG) and epileptogenic glioneuronal tumor such as gangliogliomas (GG) or pleomorphic xanthoastrocytomas (PXA). Less frequently this mutation is present in high grade glial or glioneuronal tumors such as pleomorphic xanthoastrocytomas with anaplasia, anaplastic ganglioglioma, anaplastic diffuse astrocytomas or glioblastomas. Recently, few publications were highlighting differently the impact of BRAF mutation and CDKN2A deletion, as independent prognostic factors linked to a worst outcome in low grade forms. Methods: We studied retrospectively a monocentric cohort of 12 LGGs and 9 HGG with BRAFv600e positivity. The patients were aged from 1 to 47 years. Most of the LGG were under 25 years and only 3 patients with HGGs had less than 18 years old. We focused on extended biology assessment by Next generation sequencing of the tumors and their relapses, tumor metabolomics analyses, radiology comprising MRI, PET-scanning and spectroscopy and correlate them to tumor’s evolution and its treatment. Results: Among the LGGs, we had 9 GG and 3 pilocytic astrocytomas and only one had a CDKN2A deletion and one a gain on chromosome 5. 6 had a complete surgical resection, 2 had a minimal residue and 4 had chemotherapeutic treatment after partial surgery and underwent relapses. All HGGs had a surgical resection followed by chemotherapy (mainly Stupp protocol) and radiotherapy. 5 relapsed rapidly, benefit from targeted therapy with vemurafenib and are still in long term remission. In this HGG group, we had two subgroups: 4 patients with “de novo” tumors and 5 patients with a past history of LGG tumors in the same brain region. Both were responding well to targeted treatments and all had an additional CDKN2A deletion. Specific radiological and spectroscopic signs were linked to those two groups and seem to be associated to a specific metabolomic profile in each group. Currently, we are going further in the correlation between MAPK signaling pathway and metabolomic profile to be able to predict in LGG their potential evolution. Conclusions: BRAF mutated gliomas seem to have specific radiological and metabolomic correlations associated to their biology