ERBB2 and colorectal carcinoma: The prevalence of HER2 amplification was demonstrated, in a recent retrospective study, to be significantly increased in rectal cancer (10.4%) compared with left-sided (3.6%) and right-sided CRC (2.9%) (112), while another large retrospective study (n = 717) demonstrated that HER2 overexpression by immunohistochemistry was found in 16% of rectal cancers and was associated with worse 5-year OS vs. HER2-negative patients (63.5 vs. 73.9%, P = 0.013) (113).