Prognostic effect of activated EGFR expression in human colon carcinomas: comparison with EGFR status

Abstract

Background: Evidence suggests that epidermal growth factor receptor (EGFR)-activation status may better predict the clinical behaviour of colon cancers than does EGFR expression. However, the prognostic effect of phospho-EGFR in primary colon cancer remains undefined.

Methods: Phospho-EGFR (Tyr-1173) and EGFR expression were analysed by immunohistochemistry (IHC) in tissue microarrays of TNM stage II and III colon cancers from completed adjuvant therapy trials (n=388). Staining intensity was scored and correlated with clinicopathological variables, DNA mismatch repair (MMR) status, rates of cell proliferation (Ki-67), apoptosis (caspase-3), and patient survival.

Results: Phospho-EGFR expression was detected in 157 of 388 (40%) tumours, whereas EGFR was found in 214 of 361 (59%). Although phospho-EGFR was unrelated to clinicopathological variables, strong EGFR intensity was associated with higher tumour stage (P=0.03). Tumours overexpressing EGFR (P=0.0002) or phospho-EGFR (P=0.015) showed increased Ki-67, but not caspase-3 expression. Phospho-EGFR was not prognostic. EGFR intensity was associated with worse disease-free survival (DFS) (hazard ratio (HR): 1.21 (1.03, 1.41); P=0.019) and overall survival (OS) (HR: 1.19 (1.02, 1.39); P=0.028). Tumours expressing both EGFR and phospho-EGFR had similar survival as EGFR alone. Stage and lymph node number were prognostic for DFS and OS, and histological grade for OS. EGFR was an independent predictor of DFS (P=0.042) after adjustment for stage, histological grade, age, and MMR status.

Conclusion: Phospho-EGFR and EGFR expression were associated with tumour cell hyperproliferation. Phospho-EGFR was not prognostic, whereas increased EGFR intensity was independently associated with poor DFS.

Figure 1

Immunohistochemical analysis of phospho-epidermal growth factor receptor (EGFR), EGFR, Ki-67, and caspase-3. (A) Colon carcinoma shows phospho-EGFR staining in cytoplasm of tumour cells. Magnification: × 10. (B) Colon carcinoma shows membranous EGFR staining intensity (2+). Magnification: × 10. (C) Dual staining for caspase-3 (red) and Ki-67 (brown) allows apoptotic cells to be analysed in context of proliferating cells. Magnification: × 20. The color reproduction of this figure is available on the html full version of the manuscript.

Figure 2

Univariate analysis of phospho-epidermal growth factor receptor (EGFR) staining intensity and (A) disease-free survival (DFS) for p-EGFR positive vs negative and (B) overall survival (OS) rates for p-EGFR positive vs negative in stage II and III colon carcinomas (n=388) from patients treated in adjuvant therapy trials.

Figure 3

Univariate analysis of continuous epidermal growth factor receptor (EGFR) staining intensity showing all the four categories and continuous EGFR P-value for (A) disease-free (DFS) and (B) overall survival (OS) rates in patients with stage II and III colon carcinomas (n=361) treated in adjuvant therapy trials. The prognostic effect of EGFR intensity analysed as a dichotomised variable is also shown for (C) DFS and (D) OS in these patients (n=361).