1316 - Feasibility and Usefulness of Determining EGFR and KRAS Mutations in Cytological Samples and CNB of NSCLC Using an Automated Real-Time PCR System

Abstract

ABSTRACT Background EGFR and KRAS gene mutations guide treatment selection in non-small cell lung cancer (NSCLC) patients. About 70%-80% of these patients are diagnosed at advanced stage, and mutational analysis has to be performed in small samples: core needle biopsy (CNB) and fine needle aspiration (FNA) cytology. Cobas® EGFR Mutation Test has been CE-IVD marked for the detection of 41 mutations in formalin-fixed-paraffin-embedded (FFPE) NSCLC specimens. No validation studies have been performed using cytological samples. Determining the feasibility of cobas® test on such samples is an important step to extend the benefits of molecular targeted therapy. Methods EGFR and KRAS mutations were studied in 64 non-selected samples from NSCLC patients: 31 CNB and 33 FNA. DNA was extracted directly from stained smears in FNA samples and from 4-micron sections in CNB. All samples contained at least 50% of tumor cells. All cases were studied using the cobas® test, and FNA samples were also analyzed by direct sequencing. DNA was extracted using the cobas® DNA Sample Preparation Kit. DNA concentration and DNA ratio of sample absorbance at 260/280nm (A260/280) were registered. U Mann Whitney test was used. Results CNB diagnosis was: 23 SqCC, 6 AC, 1 BAC, and 1 NSCLC-NOS. FNA diagnosis was: 26 AC, 3 SqCC, 1 BAC, 1 LCC, and 2 NSCLC-NOS. Mean DNA concentration from CNB was 23.07ng/ul ± 20.99, and from FNA samples 12.41ng/ul ± 20.04 (p Table 1 . Sanger sequencing in all FNA cases rendered concordant results. Updated results will be presented. FNA CNB EGFR WT 6 28 EXON 19 DEL 2 1 EXON 20 INS 0 1 INVALID 1 1 KRAS WT 9 26 12/13 MUTATED 9 4 INVALID 1 1 Conclusions Assessment of EGFR and KRAS mutations in FNA and CNB samples using cobas® EGFR and KRAS test is feasible and reliable. Quality of DNA (A260/280) using cobas® DNA Sample Preparation Kit in FNA samples is similar to those from CNB. Molecular results from FNA samples using cobas® test and direct sequencing are concordant, though cobas® tests are simpler, faster and easier to use. Disclosure All authors have declared no conflicts of interest.