Detection of EGFR mutations in liquid biopsy samples using allele-specific quantitative PCR: A comparative real-world evaluation of two popular diagnostic systems.

PURPOSE: The detection of epidermal growth factor receptor (EGFR) mutations in plasma cell-free DNA (cfDNA) is an auxiliary tool for the molecular diagnosis of non-small cell lung cancer (NSCLC), especially when an adequate tumor tissue specimen cannot be obtained. We compared the diagnostic accuracy of two commonly used in vitro diagnostic-certified allele-specific quantitative PCR assays for detecting plasma cfDNA EGFR mutations. METHODS: We analyzed EGFR mutations in plasma cfDNA from 90 NSCLC patients (stages I-IV) before treatment (n â€‹= â€‹60) and after clinical progression on EGFR tyrosine kinase inhibitors (n â€‹= â€‹30) using the cobas EGFR mutation test v2 (Roche Molecular Systems, Inc.) and therascreen EGFR Plasma RGQ PCR kit (Qiagen GmbH). RESULTS: There was higher concordance between plasma cfDNA and matched tumor tissue EGFR mutations with cobas (66.67%) compared with therascreen (55.93%). The concordance rate increased to 90.00% with cobas (Cohen's kappa coefficient, κ â€‹= â€‹0.80; p â€‹< â€‹0.0001) and 73.33% with therascreen (κ â€‹= â€‹0.49; p â€‹= â€‹0.0009) in advanced NSCLC patients. In treatment-naïve patients, cobas was superior to therascreen (sensitivity: 82.35% vs. 52.94%; specificity: 100% vs. 100%). In patients with clinical progression on EGFR tyrosine kinase inhibitors, EGFR exon 20 p.T790M was detected in 30% and 23% of cfDNA samples by cobas and therascreen, respectively. CONCLUSIONS: Cobas was superior to therascreen for detection of plasma EGFR mutations in advanced NSCLC. Plasma cfDNA EGFR mutation analysis is complex; therefore, the diagnostic accuracy of commercially available assays should be validated.