EGFR and metastatic colorectal cancer: Anti-epithelial growth factor receptor (EGFR) has been approved to be a targeted therapy for metastatic colorectal cancer (mCRCs) since 2009, but only a small percentage of mCRC patients shown sensitivity to this therapy, largely due to KRAS or BRAF mutations leading to constitutive activation of EGFR signaling pathway [6, 7].