Abstract 1598: EGFR mutational detection in vortex-enriched CTCs, ctDNA, and comparison to tumor tissue in non-small cell lung cancer (NSCLC) patients

Background Lung cancer is the leading cause of cancer-related mortality worldwide and 85% cases are NSCLC. Epidermal growth factor receptor (EGFR) mutations occur in 10-30% of NSCLC patients 1 . EGFR tyrosine kinase inhibitor (TKI) therapies, based on the evaluation of EGFR mutation, have shown dramatic clinical benefits. EGFR assays are mainly performed on tumor biopsies, which carry risks and expense and are not always successful 1 . In order to identify the development of secondary EGFR mutations, which cause resistance to 1 st and 2 nd generation TKI9s and an indication for therapy with a 3 rd generation drug, effective and non-invasive monitoring is needed. Liquid biopsies containing circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA), allow such monitoring over the course of the therapy 2 . The Vortex Biosciences9 VTX-1 Liquid Biopsy System enables the label-free capture of CTCs from blood samples, with high CTC recovery, purity and compatibility with downstream genomic assays on CTCs and plasma 3,4 . Our combined CTC and ctDNA EGFR assay was applied to blood samples from NSCLC patients. Method ctEGFR kit (EntroGen) was selected and validated for the detection of EGFR major mutations in a single PCR reaction, for both ctDNA and CTCs. Several blood collection tubes (BCT: EDTA, CellSave, LBGard and Streck) were tested using spiked cells, considering CTC recovery, DNA yield, and EGFR profiling. 20 blood samples were studied from 15 NSCLC patients. Plasma was extracted for ctDNA assay. CTCs were isolated from the plasma-depleted-blood using the VTX-1, immunostained and enumerated 5 . EGFR mutations were then detected in CTC+ctDNA, and compared to the tissue results. Results The VTX-1 provided a similar CTC recovery from plasma-depleted-blood and whole blood, enabling CTC+ctDNA EGFR profiling from the same tube of blood. Among the BCTs tested, LBGard obtained the best CTC capture and EGFR mutation detection performance. 10/15 patients showed the same mutations between tissue and CTC+ctDNA. For one patient with two blood draws without mutation in tissue, no mutation was detected in the first draw, while a T790M mutation was identified 6 months later. For another patient, an Exon19 deletion was detected in the ctDNA+CTC but not in the tissue, and a repeat draw confirmed the result. 4/15 patients had mutations in tissue that were missed in CTC+ctDNA. Conclusion Performing EGFR mutation analysis on the combination of ctDNA and VTX-1-collected CTCs may offer an improved sensitivity of detection over analysis of only the ctDNA, and will be potentially a useful tool for monitoring treatment and medication guidance of NSCLC patients. [1] Calabuig-Farinas et al. Transl Lung Cancer Res. 2016. [2] Sundaresan TK et al. Clin Cancer Res. 2016. [3] Kidess-Sigal E et al. Oncotarget 2016. [4] Haiyan E L et al. npj Genomic Medicine (2017) 2:34. [5] Che J. et al., Oncotarget (2016) Citation Format: Elodie Sollier-Christen, Haiyan E. Liu, Meghah Vuppalapaty, Michael Chiu, James Che, Charles Wilkerson, Nasim Barzanian, Steve Crouse, James Carroll, Melissa Matsumoto, Edward B. Garon, Jonathan W. Goldman. EGFR mutational detection in vortex-enriched CTCs, ctDNA, and comparison to tumor tissue in non-small cell lung cancer (NSCLC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1598.