KRAS and colorectal cancer: However, the overall survival is only 4.6% to 12.3% for Cetuximab monotherapy and 6.9% to 18.9% for Cetuximab in combination with chemotherapy for colorectal cancer, and almost all therapy recipients eventually develop resistance to this second line therapy due to the selective pressure for activating mutation of proto-oncogene KRAS, downstream of the EGFR signaling pathway (6–8).