EGFR and colorectal cancer: Although the possible reason of the significant association between EGFR overexpression and tumor recurrence needs to be investigated in more detail, the constitutive activation of EGFR by gene mutations and/or amplification has been shown to be related to initiation, progression, and poor prognosis in several cancers, including non-small cell lung cancer (NSCLC), colorectal cancer (CRC), squamous cell carcinoma of the head and neck (SCCHN), and glioblastoma (18, 19).