EGFR and KRAS mutations in lung carcinoma: molecular testing by using cytology specimens.

BACKGROUND: The aim of this study was to validate clinical utilization of routinely prepared cytology specimens for molecular testing to detect EGFR or KRAS mutations in lung cancer.

METHODS: From September 2009 to April 2010, the authors collected 209 cytology specimens from patients with lung cancer at the MD Anderson Cancer Center Department of Pathology. The specimens included 99 cases of endobronchial ultrasound-guided (EBUS) fine-needle aspiration (FNA), 67 cases of computed tomography (CT)-guided FNA, 27 cases of body fluid, 10 cases of ultrasound-guided of superficial FNA, and 6 cases of other cytology specimens. DNA sequencing for EGFR exons 18-21 and KRAS codons 12, 13, and 61 was performed.

RESULTS: The overall specimen insufficiency rate was low (6.2%). EBUS (4%) and body-fluid cases (3.7%) showed lower insufficiency rates than the other cases. Similar insufficiency rates were observed in smears (6.1%) and cell-block sections (6.4%). EGFR mutations were detected in 19.4% (34 of 175) of nonsmall cell lung carcinoma (NSCLC) with a significantly higher frequency in adenocarcinoma (29%, 29 of 100) than in nonadenocarcinoma (7%, 5 of 75, P = .002). KRAS mutations were detected in 23.6% (41 of 174) of NSCLCs with no statistical differences between adenocarcinoma (26%, 26 of 102) and nonadenocarcinoma (21%, 17 of 72, P = .86). Higher frequencies of EGFR mutations in exons 19 and 21 (65%) than in exons 18 and 20 were detected.

CONCLUSIONS: Our findings support clinical utilization of routinely prepared cytology specimens, including EBUS, CT/US. FNAs and body fluid specimens, as a reliable source for molecular testing to detect EGFR or KRAS mutations in patients with NSCLC.