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Molecular frontiers in lung cancer diagnosis and treament

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1G. Santis, 2R. Breen, 2A. Quinn, 2E. McLean, 2K. Tobal. 1Kings College London, London, UK, 2Guy’s & St Thomas NHS Foundation Trust, London, UK

Introduction Somatic mutations in the epidermal growth factor receptor (EGFR) are associated with significant clinical responses to tyrosine kinase inhibitors (TKIs) in patients with non-small cell lung cancer (NSCLC). Somatic mutations in the KRAS gene that encodes a signalling protein activated by EGFR are also found at high rates in NSCLC. KRAS mutations confer primary resistance to EGFR-TKIs, irrespective of EGFR mutation status. Endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration (TBNA) of mediastinal and hilar lymph nodes is being increasingly used in the diagnosis and staging of lung cancer.

Objectives The purpose of this study was to assess the feasibility of detecting EGFR and KRAS mutations in samples obtained by EBUS-TBNA.

Methods EBUS-TBNA samples were obtained via a 22 g needle placed under suction. A Consultant Cytopathologist immediately examined the obtained samples on-site to ensure adequacy of sampling for histological diagnosis. Mutation analysis was performed by “cold” PCR to amplify exons 18, 19, 20 and 21 for the EGFR gene and the regions surrounding codons 12, 13, 59 and 61 for the KRAS gene, followed by direct sequencing of these amplicons. “Cold” PCR enables the preferential amplification of mutant alleles, as compared with normal PCR.

Results Mutation analysis has thus far been performed in 17 consecutive patients with NSCLC (10 females/7 males] with confirmed lymph node metastases (9/17 (53%) adenocarcinoma; 6/17 (35%) squamous cell; 2/17 (12%) poorly differentiated). EGFR mutations were detected in 4/17 samples (24%). Three mutations were in adenocarcinoma subtype and one in poorly differentiated NSCLC (TTF-1, CK5, CK7, CK20, p63 negative by immunohistochemistry). There were three point mutations (two in exon 21, one in exon 20) and …

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