Integration of traditional molecular diagnostic tools and targeted next generation sequencing for the precise diagnosis and management of adult gliomas.

Abstract

e14011 Background: It is known that gliomas represent a wide variety of entities with varying biological features and clinical outcomes (Neuropathol Exp Neurol 2019, 78). Hence, optimal tumor classification that aids in the diagnosis and management of patients and which supports the use of specific treatment modalities is of critical importance in neuro-oncology. Targeted next-generation sequencing (NGS) has proven to be an efficient and reliable tool for identifying prognostic biomarkers for the diagnosis of CNS tumors (Neurooncol Adv 2020, 2). Here, an analysis of the impact of using NGS in addition to traditional molecular tools on tumor classification and therapy selection was analyzed; and the overall concordance was evaluated. Methods: Patients with glial tumors who were seen at our clinic between 2019-2020 and had an NGS analysis in addition to traditional molecular studies were included. All clinical data, histopathological findings and genetic reports were retrieved from the electronic medical record. We retrospectively studied each of the patients’ findings with regards to their clinical diagnosis, grade, anatomic localization; ki67 (%); TP53, IDH and ATRX mutations; as well as microsatellite instability (MSI) and additional mutational studies such as HER2 and BRAF for some patients. The concordance between the genetic and molecular data regarding TP53 and IDH mutations was also analyzed. Results: 9 patients (66.7% male) with grade 3-4 gliomas were identified at our single-center oncology institution. Most patients had a diagnosis of glioblastoma (55.6%), with a median age of 43 years at the time of diagnosis. 22.2% (2/9) had a genetic analysis through FoundationOneCDx. The concordance of the identification of mutations by NGS and immunohistochemistry (IHC) was 77.8% (7/9) for IDH mutations, and 55.6% (5/9) for TP53 mutations. NGS led to the identification of TP53 mutation in 1 patient (11%) which IHC failed to show. NGS also supported the use of targeted therapy [dabrafenib] in 1 patient (11.1%) with BRAF positivity. Conclusions: Traditional molecular diagnostic tools and targeted NGS are not perfectly concordant, but when integrated together can lead to a more comprehensive identification of genetic mutations and potential biomarkers. This can have significant implications on the precise diagnosis and potential use of targeted therapies of adult gliomas in the future.