e20525 Background: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI's) have shown dramatic clinical benefits when EGFR mutations are detected. These assays are mainly performed on tumor biopsies, which carry risks, are expensive and are not always successful. Moreover, secondary mutations, causing resistance to 1st & 2nd generation TKI’s develop during treatment and therefore mutations require ongoing monitoring. Circulating tumor cells (CTCs) or circulating tumor DNA (ctDNA) are promising for monitoring the patient over time and show enhanced sensitivity when combined1. The VTX-1 Liquid Biopsy System enables label-free capture of CTCs from blood and genomic assays downstream2. In this study, we demonstrate the sensitivity of a combined EGFR assay on VTX-1-enriched CTCs and ctDNA, using blood spiked with cancer cells & DNA and then with NSCLC patients. Methods: NSCLC cells (A549: wt, H1975: L858R+ & T790M+, HCC827: 19del+) were used to validate the assay. H1975 cells and HCC827 DNA were spiked in blood. Plasma was extracted and the plasma depleted blood was processed through VTX-1. The collected plasma and enriched cells were subjected to the detection of 19del, L858R and T790M EGFR mutations using the EntroGen ctEGFR kit. Later, blood and tumor were collected from NSCLC patients and analyzed for EGFR mutations on biopsies, ctDNA and CTCs. Results: Mutant DNA was detected for an input as low as 0.5 ng (~83 cells), with a sensitivity from 0.1% to 2% for a total DNA of 25ng (~4 cancer cells & 4000 WBCs) to 1ng (~4 cancer cells & 200 WBCs). Processing of plasma-depleted-blood with Vortex showed the same efficiency compared to whole blood. Mutations were detected from enriched cells and plasma respectively for 100 H1975 cells and 0.5ng of HCC827 DNA spiked in 2mL blood. NSCLC patients are being enrolled and results will be presented at the conference. Conclusions: The ctEGFR assay performed well on VTX-1 enriched cells and ctDNA, enabling a low cost approach to analyze EGFR mutations from a single blood tube with high sensitivity, potentially being a useful tool for guiding treatment of NSCLC patients. 1.Sundaresan, et al. Clin Cancer Res 2016. 2. Kidess-Sigal, et al. Oncotarget 2016.