A large number of somatic mutations involving the KRAS/NRAS genes have been identified, mostly associated with solid tumours such as lung cancer, pancreatic cancer and colorectal cancer, among other prevalent tumours [117,118]; in some of these tumours such as metastatic colorectal cancer, KRAS and NRAS mutations have also been associated with a poorer prognosis [119]. This evidence concerns the gene KRAS and metastatic colorectal cancer.