The pattern of epidermal growth factor receptor variation with disease progression and aggressiveness in colorectal cancer depends on tumor location.

The role of epidermal growth factor receptor (EGFR) in colorectal cancer (CRC) prognosis remains unclear despite the recent development of anti-EGFR treatments for metastatic disease. The heterogeneity of CRC may account for this discrepancy; proximal and distal CRC has been found to be genetically and clinicopathologically different. The aim of this study was to investigate the effect of tumor location on the association of EGFR with the conventional prognostic indicators (stage and grade) in CRC. Immunohistochemical assessment of EGFR was retrospectively performed in 119 primary CRC specimens and data were correlated with tumor stage and grade in the proximal and distal tumor subset. The molecular combination of EGFR with p53 (previously assessed in this sample) was similarly analyzed. EGFR positivity was detected in 34, 30 and 35% of the entire cohort, proximal and distal tumors, respectively. The pattern of EGFR clinicopathological correlation was found to differ by site. A reduction in the frequency of EGFR(+) with progression of stage and/or worsening of grade was observed proximally, whereas an opposite trend was recorded distally. Proximal tumors with stage I or with indolent features (stage I, well-differentiated) exhibited a significantly higher proportion of EGFR positivity than other tumors of this location (p=0.023 and p=0.022, respectively) or corresponding distal tumors (p=0.018 and p=0.035, respectively). Moreover, the co-existence of EGFR and high p53 staining (accounting for 11% of cases) was found in a significantly higher proportion of stage IV tumors compared to other stages (p=0.004), although only for the distal subset. Proximal and distal tumors showed various patterns of EGFR variation with disease progression and aggressiveness. This disparity provides further support to the hypothesis that these particular subsets of CRC are distinct tumor entities. It may also be suggestive of a potentially different therapeutic approach according to tumor site, particularly regarding anti-EGFR targeted treatment.