Some data suggest that the amount of mutant DNA correlates with tumor burden and can be used to identify the emergence of resistant mutations.[9-14] The concept of mutation testing from urine cfDNA has been assessed in a pilot study in patients with advanced colorectal cancer and other colorectal diseases in which KRAS mutations in urine cfDNA were concordant in 95% of cases with KRAS mutation status in tumor tissue.[15] We examine in our study whether urine and plasma cfDNA can be used as an alternative to tissue biopsies for BRAF V600E mutation testing in patients with ECD. This evidence concerns the gene KRAS and colorectal cancer.