Mutational analysis in cytological specimens of advanced lung adenocarcinoma: A sensitive method for molecular diagnosis

Introduction: The discovery that somatic mutations in the epidermal growth factor receptor (EGFR) gene are associated with sensitivity to the EGFR tyrosine kinase inhibitors (TKIs) in lung adenocarcinomas, whereas Kras mutations are associated with resistance, has generated excitement among both clinicians and researchers studying non-small cell lung cancer (NSCLC). Mutational analysis may soon be very useful in choosing among a wide range of targeted therapies to individualize treatment to tumor characteristics. This analysis would be even more useful in patients with advanced NSCLC, in whom cytological specimens are often the only material available. Methods: We analyzed 23 archived cytologic specimens of advanced/metastatic lung adenocarcinomas for mutations in EGFR exons 18 to 21, and Kras exon 2. Results: Our data show that our cytological specimens were perfectly adequate for the molecular analysis of EGFR and Kras mutations. EGFR TK domain mutations were found in three cases (13.04%) and were associated with both female gender (p = 0.02) and a nonsmoking history (p = 0.008). Moreover, we explored the relationship between EGFR mutation status and the presence of Kras mutations. Kras mutations involving codon 12 in exon 2 were found in 5 (21.73%) of the 23 adenocarcinomas and were associated, where known, with smoking habits. We never found EGFR alterations in tumors with Kras mutations. Conclusions: Our results provide oncologists with a highly accurate laboratory method to identify biological predictors of the efficacy of different therapies, and they may have an important impact on clinical practice. This method may be particularly useful in patients with advanced/metastatic NSCLC.