Analysis of KRAS and NRAS mutations in 126 patients with KRAS exon 2 wild type for metastatic colorectal cancer (mCRC) in a single institution.

e14589 Background: To know the prevalence of mutations in the RAS family in our hospital, and to determine the effect of new mutations in KRAS and NRAS in overall survival and progression-free survival. Methods: This is a retrospective observational trial. We selected a group of 126 patients with metastatic colon cancer KRAS exon 2 wild type, who received first-line treatment in our center between 01/2007 and 12/2013. Determination was performed KRAS (exon 3 and 4) and NRAS mutation (exon 2, 3 and 4) by pyrosequencing. Results: We have made the determination of 90 patients (see table below). Of the patients studied, 79% of patients remained RAS wild type. 16% had new mutations: 54% NRAS codon 61, 38% NRAS codon 12 and 8% NRAS codon 13. Regarding the clinical impact, the new RAS wild type group (n = 73) has an overall survival of 30 months (95% CI 20 to 39.7) and a progression-free survival of 8 months (95% CI 7, 5 to 10.1). Mutated RAS group (n = 13) has an overall survival of 29 months (95% CI: 5-52) and a progression-free survival of 8 months (95% CI: 5.6 to 12.3). Conclusions: The frequency of mutations in KRAS/NRAS in our center was similar to clinical trials. In our institution, overall survival and progression-free survival in RAS wild type were similar to the previously reported. RAS mutated patients were not enough to extrapolate conclusions. Mutation Total patients (n = 90) Wild type samples 73 NRAS codon 12 mutant 5 NRAS codon 13 mutant 1 NRAS codon 61 mutant 7 Failed 4