Abstract A131: Comparison of next-generation sequencing results between brain metastasis and blood in NSCLC patients with acquired EGFR-TKI resistance other than T790M mutation

Abstract

Abstract Background: Mechanisms of acquired resistance for EGFR tyrosine kinase inhibitor (TKI) in non-small cell lung cancer (NSCLC) has been studied broadly, and T790M mutation, bypass signaling, and phenotype change have been suggested. Questions remain in terms of the selection of sub-clones according to the sites during EGFR TKI therapy, especially in brain due to blood-brain barrier. Three metastatic NSCLC patients harboring sensitive EGFR mutation were treated with EGFT TKI with good response but became refractory and symptomatic brain oligo-metastasis occurred. Metastectomy was done and next-generation sequencing (NGS) was done with the brain tissue and blood. Methods: Fresh brain metastasis tissue was obtained during surgery and frozen in liquid nitrogen. Blood sampling was done within a week of the surgery and plasma was used for NGS. Amplicon sequencing (Thunderbolt) was performed. Library preparation and quality control sequencing amplicon libraries were prepared using ThunderBolts Cancer Panel, according to the manufacturer's instructions. The ThunderBolts Cancer Panel uses 230 amplicons to interrogate mutations and hotspots in 50 oncogenes, tumor suppressors, and drug resistance markers. Results: All 3 brain tissues had the same sensitive EGFR mutation (exon 19 deletion) as initial presentation, with PDGFRA, APC and TP53 mutations, while in the plasma, PDGFRA and APC mutations were identified in the 3 patients. From case 1, PDGFRA, APC, MLH1, and EGFR mutations were identified in the plasma, and additional PIK3CA, KDR, TP53, ERBB2, and GNA11 mutations were found in the brain. From case 2, PDGFRA, APC, EGFR, MET, PTEN, HRAS, and TP53 mutations were found in the plasma, and in the brain, PIK3CA, KDR, and ERBB2 mutations were identified in addition. From case 3, PDGFRA, APC, HRAS, and TP53 mutations in the plasma, and additional EGFR mutation in the brain. Conclusions: Our data identified several additional mutations in brain metastasis compared to the plasma from patients with acquired EGFR TKI resistance, other than T790M mutation. Every mutation in the blood sample was identified in the brain tissue, while additional mutations were found in the brain tissue. Citation Format: Hee Yeon Lee, Jeong-Oh Kim, Jin-Hyoung Kang. Comparison of next-generation sequencing results between brain metastasis and blood in NSCLC patients with acquired EGFR-TKI resistance other than T790M mutation [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A131.