Epidermal growth factor receptor (EGFR) status in primary colorectal tumors correlates with EGFR expression in related metastatic sites: biological and clinical implications.

BACKGROUND: Epidermal growth factor receptor (EGFR) plays an important role in the pathogenesis of colorectal cancer (CRC). There are several potential strategies to target EGFR. However, monoclonal antibodies and low molecular weight tyrosine kinase inhibitors are the most advanced in clinical development. The majority of studies so far have merely required EGFRs to be expressed by CRC cells. The detection of EGFR expression is usually performed by immunohistochemistry (IHC) in the primary tumor. There are few data regarding the EGFR status in the corresponding distant metastases. PATIENTS AND METHODS: EGFR status was analyzed by IHC in 80 patients (31 male, 49 female) with CRC (70 colon, 10 rectum) and at least one distant metastatic lesion. Metastatic sites analyzed (n=80) were liver (79 patients) and lung (one patient).
RESULTS: EGFR reactivity was similar in the primary tumor and the related metastases. Among the 80 paired primary/metastatic tumors, only five (6.3%) showed discordance in EGFR status: two cases with EGFR expression in the primary tumor but not in the metastasis, and three samples with EGFR expression in the metastasis but not in the primary tumor.
CONCLUSIONS: Between the paired primary tumors and distant metastatic lesions, 94% of samples had concordant EGFR status when analyzed by IHC.