Epidermal growth factor receptor analyses in colorectal cancer: A comparison of methods

Abstract

EGFR immunohistochemistry (IHC) status is not a reliable predictive marker for response to EGFR-targeted therapies. The present study compares the EGFR status at DNA, RNA and protein level. Blood samples, corresponding normal colon and colorectal cancer tissue were collected from 199 colorectal cancer (CRC) patients. EGFR status was evaluated by FISH analysis, real-time RT-PCR, ELISA and IHC. A polymorphism in the EGFR promoter was evaluated by PCR analysis. The EGFR levels by different methods were mutually compared. Seventy-eight percent of primary tumours and corresponding lymph nodes had equivalent EGFR status (28/34). There was a tendency to higher median protein level (by ELISA) in IHC positive patients compared to IHC negative patients (p=0.086). The median EGFR gene expression level was significantly lower in tumours than in the normal colon with no difference according to IHC status. No tumours had increased gene copy number by FISH. EGFR Sp1-216 polymorphism analysis showed a tendency for different EGFR tumour protein levels and gene expression levels according to the different genotypes. The results show a poor correlation between EGFR status at DNA, RNA and protein level. The predictive value of a combination of methods needs further evaluation in the clinical setting.