Routine detection of EGFR mutations in patients with NSCLC: A comparative study of three alternative methods in 105 patients

Abstract

7184 Background: The efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) has been reported in lung adenocarcinoma patients with tumoral EGFR mutations. Those mutations were found mainly by direct genomic sequencing on snap-frozen surgical specimens. Conversely, TKIs are used in metastatic patients who do not undergo tumor resection. In these patients, there is a need for routine sensitive molecular procedures, to overcome the small size of non-surgical bronchoscopy paraffin-embedded biopsy samples. Methods: Patients were selected on clinical and pathological characteristics: never (n = 43) or former smokers, patients with non-squamous NSCLC (n = 105) or patients with bronchioloalveolar adenocarcinoma (n = 34). Direct genomic sequencing assay was performed as reported elsewhere. Denaturing, high-performance, liquid chromatography (DHPLC) assay was performed with EGFR-specific primers that amplify exons 18, 19, and 21. A multiplex, allele-specific, oligonucleotide PCR (MASO-PCR) assay was carried out with a set of primers that identify the 14 most frequent molecular events described for the EGFR gene, which covers 90% of EGFR gain-of-function mutations described to date. Results: 123 samples were screened from 105 non-squamous NSCLC patients (female/male ratio = 0.84). Non-surgical biopsy specimens were available in 38 patients. EGFR mutations were detected by at least two of three procedures in 18/105 patients (17%). In paraffin-embedded specimens with low tumor content, EGFR heterozygous mutations were found either by MASO-PCR alone (n = 2, confirmed in the matched surgical sample by another procedure), or both by MASO-PCR and DHPLC (n = 16); they were missed by nucleotidic sequencing in 6 samples. 18 patients received TKI. 6 dramatic responses were achieved in patients with EGFR mutation, while no mutation could be found in non-responsive patients. Overall disease control was obtained in 8/18 patients (44%). Conclusions: MASO-PCR and DHPLC appear more sensitive than direct sequencing in non-surgical paraffin-embedded biopsies, which represent the bulk of samples in lung cancer patients. We propose that the cost-effective MASO-PCR be used for routine screening of EGFR mutations in NSCLC patients. No significant financial relationships to disclose.