Detection and comparison of peptide nucleic acid-mediated real-time polymerase chain reaction clamping and direct gene sequencing for epidermal growth factor receptor mutations in patients with non-small cell lung cancer

EGFR tyrosine kinase inhibitors (EGFR-TKIs) are recommended as first-line therapy in patients with advanced, recurrent, or metastatic non-squamous non-small cell lung cancer (NSCLC) that have active EGFR mutations. The importance of rapid and sensitive methods for the detection of EGFR mutations is emphasized. The aim of this study is to examine the EGFR mutational status by both direct DNA sequencing and peptide nucleic acid (PNA)-mediated real-time PCR clamping and to evaluate the correlation between the EGFR mutational status and the clinical response to EGFR-tyrosine kinase inhibitors. Clinical specimens from 240 NSCLC patients were analyzed for EGFR mutations in exons 18, 19, 20 and 21. All clinical data and tumor specimens were obtained from 8 centers of the Korean Molecular Lung Cancer Group (KMLCG). After genomic DNA was extracted from paraffin-embedded tissue specimens, we performed PNA-mediated real-time PCR clamping and direct DNA sequencing for the detection of EGFR mutations. Of 240 tumor samples, PNA-mediated PCR clamping was used to detect genomic alterations in 83 (34.6%) samples, including 61 identified by sequencing and 22 additional samples (10 in exon 19, 9 in exon 21, and 3 in both exons); direct DNA sequencing was used to identify a total of 63 (26.3%) mutations that contained 40 deletion mutations in exon 19 (63.5%) and 18 substitution mutations (28.6%) in exon 21. PNA-mediated PCR clamping was used to identify more mutations than clinical direct sequencing, whereas clinical outcomes were not significantly different between the groups harboring activating mutations detected by each method. These data suggest that PNA-mediated real-time PCR clamping exhibits high sensitivity and is a simple procedure relative to direct DNA sequencing that is a useful screening tool for the detection of EGFR mutations in clinical settings.