Ras Mutations Concordance In Circulating Tumor Dna (Ctdna) And Tissue In Metastatic Colorectal Cancer (Mcrc): Rasanc, An Ageo Prospective Multicenter Study.

11509Background: RAS mutational status is required to prescribe anti-EGFR antibodies in mCRC. In comparison to molecular testing from tumor tissue, the characterization of RAS mutations in ctDNA is a promising and credible way to shorten the workflow. This study reports for the first time the performance of plasma testing in a large prospective series. Methods: Blood samples were prospectively collected before 1st line chemotherapy in mCRC patients. ctDNA was centrally assessed by NGS using the colon lung cancer V2 Ampliseq panel and by methylation digital PCR assay (WIF or NPY). Tumor tissue testing was done according to routine practice in each center. We expect a minimal kappa coefficient of 0.7 to reflect concordance. In order to have a precision of ± 0.07 with an estimated 5% of non-exploitable data 425 pts had to be included. Results were analyzed separately in the whole study population and in the subgroup of pts with ctDNA evidenced either by the presence of at least 1 mutation or by the presence ...