Purpose: Amphiregulin (AREG) and epiregulin (EREG) are ligands of EGFR. Predictive information for anti-EGFR treatment in metastatic colorectal cancer (mCRC) was observed, but data for other agents is limited. Experimental Design: Ligand mRNA expression; RAS, BRAF, PIK3CA mutations; and EGFR expression were assessed by qRT-PCR, pyrosequencing, and IHC, respectively, in mCRC tumor tissue of patients participating in the randomized controlled trials FIRE-1, CIOX, and FIRE-3. Normalized mRNA expression was dichotomized using median and third quartile. Overall (OS) and progression-free survival (PFS) were estimated by Kaplan–Meier method including univariate and multivariate Cox regression analyses. Penalized spline regression analysis tested interaction of mRNA expression and outcome. Results: Of 688 patients with available material, high AREG expression was detected in 343 (>median) and 172 (>3rd quartile) patients. High AREG expression was associated with significantly higher OS [26.2 vs. 21.5 months, HR = 0.80; 95% confidence interval (CI), 0.68–0.94; P = 0.007], PFS (10.0 vs. 8.1 months, HR = 0.74; 95% CI, 0.63–0.86; P = 0.001), and objective response rate (63.1% vs. 51.6%, P = 0.004) compared to low expression at both threshold values. This effect remained significant in multivariate Cox regression analysis (OS: P = 0.01, PFS: P = 0.002). High AREG mRNA expression interacted significantly with the efficacy of cetuximab compared with bevacizumab (OS: P = 0.02, PFS: P = 0.04) in RAS WT mCRC. Conclusions: High AREG mRNA expression is a favorable prognostic biomarker for mCRC which interacted significantly with efficacy of anti-EGFR treatment.

Background: The EGFR (epithelial growth factor receptor) ligands amphiregulin (AREG) and epiregulin (EREG) have been considered as predictors for EGFR-antibody efficacy. The effect of AREG and EREG expression levels in primary tumor samples on the outcome of bevacizumab-treated patients is unknown.Patients and Methods: Formalin-fixed paraffin-embedded (FFPE) tumor samples from surgically removed primaries of the AIO KRK-0207 trial have been tested for AREG and EREG expression. The AIO KRK-0207 trial was a randomized phase-3 study to investigate the best maintenance strategy after oxaliplatin/fluoropyrimidine plus bevacizumab induction treatment in patients with mCRC. Association of AREG and EREG levels with outcome parameters were investigated, taking into account RAS and BRAF mutations.Results: A total of 331 tumor samples had measurable AREG and EREG tissue levels. In the total cohort using continuous expression levels, higher logAREG and logEREG levels were associated with a significant longer overall survival (OS) (HR 0.80; p = 0.003 and HR 0.78; p = 0.001, respectively). The subgroup of BRAF mutant tumors displayed significantly lower AREG and EREG levels compared to wild-type tumors. The prognostic effect of AREG and EREG expression was limited to the double wild-type subpopulation, whereas in the RAS mutant and BRAF mutant subgroups no prognostic effect was detected.Conclusion: Low logAREG and logEREG levels are associated with a shorter OS in oxaliplatin/fluoropyrimidine plus bevacizumab treated patients. As low AREG and EREG level are associated with BRAF mutations, the prognostic value of EREG and AREG levels is limited to the RAS and BRAF wild-type subpopulation.

4026 Background: Amphiregulin ( AREG) and epiregulin ( EREG) were discussed as biomarkers for treatment of metastatic colorectal cancer (mCRC). Data from randomized controlled trials (RCT) are limited. Methods: AREG and EREG mRNA expression by RTqPCR in relation to housekeeping genes were available from 688 patients of three RCT (FIRE-1, n = 192, FUFIRI vs. mIrOx; CIOX, n = 113, cetuximab + CAPIRI/CAPOX; FIRE-3, n = 383, FOLFIRI+cetuximab/bevacizumab) and were normalized to their respective range of each trial with median and 3rd quartile as threshold values. Kaplan-Meier estimated overall survival (OS) and progression-free survival (PFS). Cox regression analysis calculated hazard ratio (HR) and 95% confidence interval (95% CI). Overall response rate (ORR) was compared by chi square test. Results: Across all trials, high AREG mRNA expression appeared as strong prognostic biomarker for OS, PFS and ORR for all threshold values. In RAS wildtype patients, high AREG expression was associated with better OS and PFS for cetuximab but not bevacizumab treatment. (Table) No effects were seen for epiregulin when all trials were analysed together. Conclusions: High AREG mRNA expression appeared as strong prognostic biomarker in mCRC. Positive predictive information might exist for cetuximab treatment. [Table: see text]