P11.08 Defining EGFR amplification status for clinical trial inclusion. (6th September 2019)

• Record Type: Journal Article
• Authors: French, P; Eoli, M; Sepulveda, J; de Heer, I; Kros, J M; Walenkamp, A; Frenel, J; Franceschi, E; Clement, P; Weller, M; Ansell, P; Looman, J; Bain, E; Morfouace, M; Gorlia, T; van den Bent, M
• Is Part Of: Neuro-oncology. Volume 21(2019)Supplement 3
• Page Start: iii43
• Page End: iii44
• Publication Date: 2019-09-06
• Subjects: Brain Neoplasms -- Periodicals; Brain -- Tumors -- Periodicals; Brain -- Cancer -- Periodicals; Nervous system -- Cancer -- Periodicals; 616.99481
• DOI: 10.1093/neuonc/noz126.154
• Languages: English
• ISSNs: 1522-8517

Abstract

Abstract: BACKGROUND: Precision medicine trials targeting the epidermal growth factor receptor (EGFR) in glioblastoma patients require selection for EGFR -amplified tumors. However, there is currently no golden standard in determining the amplification status of EGFR or EGFRvIII expression. Here, we aimed to determine which technique and which cut-offs are suitable to determine EGFR amplification status. MATERIAL AND METHODS: We compared fluorescent in-situ hybridization (FISH) and RT-qPCR data from patients screened for trial inclusion into the Intellance 2 clinical trial, with data from a panel-based next generation sequencing (NGS) platform (both DNA and RNA). RESULTS: By using data from >1000 samples, we show which cut-offs are optimal to determine EGFR gene amplification by FISH. Our data also show that gene amplification (as determined by FISH) correlates with EGFR expression levels (as determined by RT-qPCR) with ROC analysis showing an under the curve area of up to 0.902. EGFR expression as assessed by RT-qPCR therefore may function as a surrogate marker for EGFR amplification. Our NGS data shows that EGFR copy numbers can strongly vary between tumors with levels ranging from 2 to more than 100 copies per cell. Levels exceeding 5 gene copies can be used to define EGFR-amplification by NGS; below this level FISH detects very few (if any) EGFR amplified nuclei and none of the samples express EGFRvIII . CONCLUSION: Our data from central laboratories and diagnostic sequencing facilities, using material from patients eligible for clinical trial inclusion, help defining the optimal cut-off for various techniques to determine EGFR amplification for diagnostic purposes.