Abstract A02: Targeted deep sequencing of second biopsy tissues from patients with acquired resistance (AR) to EGFR tyrosine kinase inhibitors harboring EGFR mutations: Preliminary results.

Abstract

Abstract Background: Patients with EGFR activating mutation in non-small cell lung cancer (NSCLC) eventually develop AR to EGFR tyrosine kinase inhibitors (TKI) after durable and high response. Several mechanisms of AR to EGFR TKIs identified include T790M gatekeeper mutation, PIK3CA mutation, C-met amplification, transformation into small cell carcinoma or epithelial-mesenchymal transition (EMT). In the present study, to identify other genetic alterations, we performed targeted deep sequencing for over 700 hotspots in 50 cancer-related genes using next generation sequencing (NGS) technology. Methods: Genomic DNA was extracted from FFPE tissue or pleural/pericardial fluid or primary culture cells of 57 NSCLC patients who developed AR to EGFR TKIs. Amplicons NGS libraries for 50 oncogenes included in Ion AmpliSeqTM Cancer Hotspot Panel v.2 were generated and sequenced in the Ion PGM Sequencer. Variant caller included in Torrent Suite Software was utilized to identify mutations in the samples, annotation was performed with IonTorrentTM Software. Results: All 57 patients were treated with EGFR TKIs, gefitinib (n=39), erlotinib (n=17), or afatinib (n=1) as first-line or later line of therapy. 65% were female, 74% never smokers, median age of 58 years (range 25-77) and 98% were adenocarcinoma. 31 patients have exon 19 deletion and 14 with L858R at baseline. The median PFS for EGFR TKIs was 11 months (range 4-63). Targeted deep sequencing of second biopsy identified recurrent coexisting mutations of T790M in 52.6%. Other frequently altered genes include mutation of CTNNB1 (n=9), c-KIT (n=7), c-met (n=7), SMARCB1 (n=5), PDGFRA (n=5), PTEN (n=2), NRAS (n=2), and PIK3CA (n=1). However, in order to investigate whether these recurrent mutations observed in second biopsy represent genes associated with AR or pre-existing genes, targeted deep sequencing of available paired baseline samples will be performed and updated. Conclusions: We found that NGS technology is feasible in FFPE tissues. Although T790M mutation confers the most common resistant mechanism to EGFR TKI, several detected genetic mutations are novel observations which might provide potential candidates for AR mechanisms. Further validation results will be discussed. Citation Format: Myung-Ju Ahn, Youngwook Kim, Kyoung-Mee Kim, Yoon-la Choi, Joungho Han, EunHye Jho, Joung-Mu Sun, Jin-Sock Ahn, Keunchil Park. Targeted deep sequencing of second biopsy tissues from patients with acquired resistance (AR) to EGFR tyrosine kinase inhibitors harboring EGFR mutations: Preliminary results. [abstract]. In: Proceedings of the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer; 2014 Jan 6-9; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2014;20(2Suppl):Abstract nr A02.