KRAS and colorectal carcinoma: Clearly, there are a number of confounding factors, such as the exact nature of KRAS mutations (G13D or other), levels of EGFR expression, EGFR mutations, first or later lines of therapy, chemotherapeutic backbone (irinotecan or oxaliplatin), or even administration regimen (infusion or bolus), which all seem to interplay and ultimately can affect the outcome of anti-EGFR therapy in CRC patients.