Abstract 5680: Clinical significance of low frequency EGFR and KRAS mutations of cell free DNA using Ion AmpliSeq Cancer Hotspot Panel in lung cancer patients

Cell free DNA (cfDNA) present in the blood stream shows great potential as a useful cancer marker for molecular diagnosis and cancer progression monitoring. Especially, analyzing the cfDNA with Next Generation Sequencing (NGS) technology allows high through put examination of various genes concurrently at a low cost. However, there are still debates regarding clinically meaningful variant frequency to identify mutations in cfDNA, especially with ultra-deep sequencing. In this study, we examined the clinical utility of Ion AmpliSeq Cancer Hotspot Panel v2 (ICP; Ion Torrent) with Proton platforms. ICP, covering 2800 COSMIC mutations from 50 cancer genes was used to analyze cfDNA of 125 serum samples from lung cancer patients. The percentage of on target was 92% with mean depth of 22,868x. We identified aberrations of TP53 (72%), EGFR (43%), PTEN (26%), PIK3CA (26%), BRAF (16%), KRAS (14%), KIT (10%) and RET (10%) with the cut-off criteria of variant frequency >0.1% and p