Detection and comparison of EGFR mutations in matched tumor tissues, cell blocks, pleural effusions, and sera from patients with NSCLC with malignant pleural effusion, by PNA clamping and direct sequencing

Peptide nucleic acid (PNA)-mediated real-time PCR clamping has higher sensitivity than conventional direct sequencing for detecting mutations. Pleural effusion and serum may provide good samples in which to detect epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) patients. We studied 37 NSCLC patients with malignant pleural effusion. EGFR mutations were assessed by PNA clamping and direct sequencing using tumor tissues, cell blocks, pleural effusion, and serum. Concordance between PNA clamping and direct sequencing results, and the diagnostic performance of pleural effusion were investigated. The κ coefficients for the two methods were 0.68 (p = 0.0007), 0.91 (p < 0.0001), 0.75 (p < 0.0001) and -0.01 (p = 0.8639) for tissues, cell blocks, pleural effusion, and serum, respectively. The diagnostic performance of pleural effusion compared with the combination of tumor tissue and cell blocks showed 89% sensitivity, 100% specificity, positive predictive value of 100%, and negative predictive value of 95% by PNA clamping, and 67% sensitivity, 90% specificity, positive predictive value of 75%, and negative predictive value of 86% by directing sequencing. A patient in whom an EGFR mutation was identified in pleural effusion only by PNA clamping showed a significant response to EGFR tyrosine kinase inhibitor (EGFR-TKI) treatment. In contrast to the limited role of serum samples, pleural effusion had a diagnostic performance for the detection of EGFR mutations in NSCLC that was comparable to that of tumor tissues and cell blocks. The diagnostic performance of PNA clamping was good compared with that of direct sequencing. A more sensitive and accurate detection of EGFR mutations would benefit patients by allowing a better prediction of the response to EGFR-TKI treatment.