KRAS and colorectal carcinoma: For example, understanding that KRAS and BRAF are both downstream of EGFR explains why the EGFR inhibitor cetuximab is ineffective in KRAS-mutated CRC and why using cetuximab in combination with the BRAF inhibitor encorafenib is now FDA-approved therapy for patients with a previously treated V600E BRAF mutated CRC [3,4,5,6].