In addition to KRAS mutational status, tumor-sidedness is associated with response to anti-EGFR therapy in CRC.25 The initial observations supporting this practice came from the translational work and retrospective analyses of phase III studies, such as CALGB/SWOG 80405 (NCT00265850) and FIRE-3 (NCT00433927), which explored anti-EGFR therapy plus chemotherapy vs anti-VEGF plus chemotherapy KRAS/NRAS wild-type mCRC tumors.26 This evidence concerns the gene KRAS and colorectal carcinoma.