Abstract 482: Recurrent glioma with lineage conversion from oligodendroglioma to astrocytoma: Another facet of glioma evolution during recurrence

Abstract

Abstract Background: Following the introduction of the molecular classification of gliomas by the WHO in 2016, molecularly-proven lineage conversion during glioma recurrence has never been reported. Methods: We analyzed two cases of recurrent glioma that began as oligodendroglioma, both histologically and molecularly, but converted to astrocytoma over episodes of recurrence. Results: The cases were initially diagnosed as oligodendroglioma with 1p/19q-codeletion and mutation of isocitrate dehydrogenase 1 (IDH1)-R132H. The recurrent tumors showed loss of alpha-thalassemia/mental retardation X-linked (ATRX) expression, strong P53 positivity, and 1p/19q-nondeletion. Next generation sequencing (NGS) analysis performed on the first case confirmed the transition of molecular traits from oligodendroglioma to astrocytoma. An IDH mutation of R132H was preserved in the episodes of recurrence, but ATRX and TP53 mutations were newly acquired and TERT promoter mutation C228T was lost at the most recent recurrence. Conclusions: The issue in question for the presented cases is whether the original tumors were pure oligodendrogliomas that then transdifferentiated into astrocytomas, or whether the original tumor was an oligoastrocytoma having oligodendroglioma cells that outnumbered the astrocytoma cells and where the astrocytoma cells becoming more dominant over the episodes of recurrence. With the recognition of the possibility of lineage conversion, our study suggests that molecular examination should be performed to adjust therapeutic strategies in recurrent gliomas. Indeed, our observation of lineage conversion in glioma recurrence calls into question the current distinction drawn between oligodendroglioma, astrocytoma and oligoastrocytoma, rather than simply bidding “farewell to oligoastrocytoma”. Citation Format: Kyung-Hwa Lee, Tae-Young Jung, Shin Jung, Jae-Hyuk Lee, Kyung-Keun Kim, Hangun Kim, Kyung-Sub Moon. Recurrent glioma with lineage conversion from oligodendroglioma to astrocytoma: Another facet of glioma evolution during recurrence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 482.