In addition, a number of retrospective studies have provided evidence that primary resistance to EGFR inhibitors in colorectal cancer could be correlated to deregulation of other intracellular downstream effectors of EGFR, such as mutation in BRAF or PIK3CA genes, loss of PTEN expression, and amplification of KRAS [7,8,9,10]. Here, EGFR is linked to colorectal cancer.