OS3.3 Radiological characteristics and natural history of adult IDH wild type astrocytomas with TERT promoter mutations

BACKGROUND: Adult IDH-wildtype astrocytomas with TERT promoter mutations (TERTp) are associated with a poor prognosis. The aim of the present study was to analyze their radiological presentation and natural history. MATERIAL AND METHODS: We retrospectively reviewed the characteristics of 40 IDH-wildtype TERTp-mutant astrocytomas (grade II n=19, grade III n=21) and compared them to those of 114 IDH-mutant lower grade gliomas (LGG), of 92 IDH-wildtype TERTp-mutant glioblastomas and of 15 IDH-wildtype TERTp-wildtype astrocytomas. RESULTS: Most cases of IDH-wildtype TERTp-mutant astrocytomas occurred in patients aged >50 years (88%) and presented as infiltrative lesions without contrast enhancement (73%) that were localized in the temporal and/or insular lobes (37.5%) or corresponded to a gliomatosis cerebri (43%). Thalamic involvement (33%) and extension to the brainstem (27%) were frequently observed, as was gyriform infiltration (33%). This radiological presentation was different from that of IDH-mutant LGG, IDH-wildtype TERTp-mutant glioblastomas, and IDH-wildtype TERTp-wildtype astrocytomas. Tumor evolution before treatment initiation was assessable in 17 cases. Ten cases demonstrated a rapid growth characterized by the apparition of a ring-like contrast enhancement and/or a median velocity of diametric expansion (VDE) ≥ 8 mm/year but 7 cases displayed a slow growth (VDE < 8 mm/year) that could last several years before anaplastic transformation. Median overall survival of IDH-wildtype TERTp-mutant astrocytomas was 27 months. CONCLUSION: IDH-wildtype TERTp-mutant astrocytomas typically present as non-enhancing temporo-insular infiltrative lesions or as gliomatosis cerebri in patients aged >50 years. In the absence of treatment, although rapid tumor growth is frequent, an initial falsely reassuring, slow growth can be observed.