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 ​= ​60) and after clinical progression on EGFR tyrosine kinase inhibitors (n ​= ​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 ​= ​0.80; p ​< ​0.0001) and 73.33% with therascreen (κ ​= ​0.49; p ​= ​0.0009) in advanced NSCLC patients. In treatment-naive 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.