P3.02b-018 Detection of Epidermal Growth Factor Receptor Mutations in Circulating Cell-Free DNA versus Tumor Biopsy: Topic: EGFR Biomarkers

Abstract

Epidermal growth factor receptor (EGFR) mutations are predictive marker of EGFR-tyrosine kinase inhibitor (TKI) therapy. We compared the sensitivity of EGFR mutation detection techniques between matched tumor tissue and peripheral blood sample in patients with lung adenocarcinoma. We collected the paired samples from plasma and paraffin-embedded tumor tissue in 202 patients before EGFR-TKIs. DNA extraction was performed using the QIAamp MinElute virus spin kit and EGFR mutation analysis was done by two detection methods. One is the PNAClampTM which is the PNA-based PCR clamping that selectively amplifies only the mutated target DNA sequence as minor portion in mixture with the major wild type DNA sequences. The other is the PANAMutyperTM EGFR kit, which use PNA clamping-assisted fluorescence melting curve analysis to perform mutation detection and genotyping. The degree of agreement was evaluated by Cohen's kappa value. The EGFR mutation rates by PANAMutyperTMR and PNAClampTM were 51.0% vs. 47.0% in tissue, and 22.2% vs. 11.4% in plasma sample, respectively. Overall concordance rates and the degree of agreement between tissue and plasma samples was better in PANAMutyperTMR (69.3%, k=0.393, p<0.001) than PNAClampTM (62.3%, k=0.211, p<0.001). Sensitivity of plasma EGFR mutations was higher (41.7% vs. 22.1%, p<0.001) and false negative rate was lower in PANAMutyperTMR test (58.3% vs. 77.9%, p<0.001). Response to EGFR-TKI was correlated with plasma EGFR mutation by PANAMutyperTMR (p=0.025) unlike PNAClampTM (p=0.829). The sensitivity and concordance rate of PANAMutyperTMR test were better than standard PNAClampTM test. So this technique can be useful to detect EGFR mutation in circulating cell-free DNA sample.