Abstract 822: KRAS and BRAF mutation analysis using formalin fixed and paraffin embedded colorectal tissue and fine needle aspiration biopsies from thyroid

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Point mutations in codons 12, 13 and 61 of the KRAS gene and in codon 600 of the BRAF gene can be identified in neoplastic tissue from many different organs. KRAS mutations are present in approximately 40% of sporadic colorectal adenocarcinoma and this analysis is important to determine response to anti-EGFR targeted therapies. BRAF mutations are present in approximately 40% of the papillary thyroid carcinoma and 10% sporadic colorectal adenocarcinoma. BRAF mutation V600E is associated with more aggressive thyroid tumors and its detection is important for thyroid cancer prognosis. Detection of BRAF mutation in colorectal cancer is also useful for characterizing sporadic tumors. A method developed in-house to identify mutations in KRAS (codos 12 and 13) was validated using formalin-fixed paraffin-embeded tissue (FFPE) from 31 surgical specimens diagnosed with metastatic colorrectal cancer. Similarly, a method for BRAF mutation analysis (codon 600) was developed and validaded using 39 smears from fine needle aspiration biopsies (FNAB) of the thyroid. Cytology analysis was performed to confirm the presence of neoplastic or suspected lesions. DNA was extract from 1-4 slides containing the FFPE tissue sections or smears from the FNAB. Mutation analyses were performed by Sanger sequencing and results were compared with pyrosequencing. Automatic analysis of nucleotide sequences using the SeqScape software (Applied Biosystems) was also implemented. There was 85.7% and 100% concordance between Sanger sequencing and pyrosequencing for KRAS and BRAF mutation analysis, respectively. Precision intra- and inter-assay analysis were concordant, with the exception of one sample with KRAS mutation. Sensitivity was evaluated using pools containing different proportions of mutated and non-mutated DNA from cell lines. Data analysis by visual inspection resulted in the detection of the mutant allele in samples with at least 10% of mutated DNA. However, KRAS and BRAF mutations analysis using SeqScape software detected the mutant allele in pools containing at least 30% and 25% of mutated DNA, respectively. This is in accordance with the overall sensitivity observed by standard sequencing analysis. In conclusion, KRAS and BRAF mutation analysis can be successfully performed using small amount of tissue sections from FFPE specimens and smears from FNAB. This material has the advantage of requiring small amounts of sample and also allows cytology review of the tissue content prior to molecular analysis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 822.