Abstract:

BACKGROUND: High amplification of epiregulin (EREG) and amphireglin (AREG) in tumour tissues has been previously reported to be associated with better outcome in metastatic colorectal cancer (mCRC) patients who were treated with anti-EGFR antibodies. Here we investigated associations between the expression of other candidate prognostic biomarkers and outcome in mCRC patients receiving similar treatment.
METHODS: The relative mRNA levels of seven genes including ERBB2, MET, VEGFA, EREG, AREG, PTEN and ERCC1 between tumour (T) and non-tumour (NT) tissue sections were analysed by quantitative real-time PCR. Relative mRNA values, that is, T/NT ratios, of target genes were calculated and hazard ratios (HRs) for each gene of interest were adjusted for age, gender, performance status, minor RAS mutations and other clinicopathological variables which exhibited P-values<0.1 on the basis of univariate analysis.
RESULTS: Among 108 cases who received anti-EGFR antibodies, there were 96 cases of KRAS exon2 wild-type patients enroled in this study. When the cutoff values for relative mRNA levels were set to the upper 25th percentile of all patients, there were statistically significant differences in overall survival (OS) between the patients with high and low levels of EREG (HR: 0.326, 95% CI: 0.136-0.772, P=0.011), ERBB2 (HR: 1.31, 95% CI: 1.084-1.652, P=0.040), MET (HR: 2.48, 95% CI: 1.356-5.463, P=0.026), and VEGF-A (HR: 1.29, 95% CI: 1.036-1.606, P=0.046). In addition, patients with high ERBB2 had shorter progression-free survival (PFS) compared with low ERBB2 (HR: 1.98, 95% CI: 1.062-3.850). There were no significant differences in PFS and OS with respect to relative expression levels of PTEN and ERCC1. The prognostic role of AREG was evaluated in only T sections, as the mRNA expression level of this gene was mostly (91% cases) undetectable in NT sections. Patients with high AREG had longer OS compared with low AREG (HR: 0.227, 95% CI: 0.095-0.808).
CONCLUSIONS: Our study has shown that higher T/NT ratios of ERBB2, MET and VEGFA mRNA were associated with worse OS in mCRC patients treated with anti-EGFR antibodies, with higher EREG and AREG were associated with better prognosis in the same setting. These findings will contribute the further understanding and management of anti-EGFR antibody treatment in mCRC patients.

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