Background: Epidermal growth factor receptor (EGFR) turnover is a highly regulated process controlling the amount of receptor proteins available for antibody binding. The ubiquitin proteasome system (UPS) is responsible for EGFR degradation. The single nucleotide polymorphism (SNP) rs895374 is located in UbcH7, an E2 ligase conducting neddylation of HECT E3 ligases involved in EGFR degradation. Neddylation activates E3 ligases and switches the balance between degradation and recycling towards degradation. We have previously reported that rs895374 correlates with progression free survival (PFS) in patients (n=108) treated with cetuximab in two phase II studies of further-line treatment. The aim of this study was to validate the predictive value of rs895374 in an independent cohort of cetuximab treated patients with a cetuximab-free chemotherapy arm serving as negative control. Methods: Genomic DNA was isolated from tissue samples of 455 patients (median age 64 years, male 64.2%) treated in first-line with either FOLFIRI cetuximab (n=218) or FOLFIRI bevacizumab (n=237) enrolled in the FIRE-3 trial (NCT00433927). The cetuximab arm served as validation for our previous results whereas the bevacizumab arm served as negative control arm to confirm the predictive value of this SNP. Results: The minor allele A was associated with shorter PFS in the FOLFIRI + cetuximab validation set, (10.5 months vs. 8.2 months; logrank p=0.005; HR 0.66 (0.47-0.89)). In the FOLFIRI plus bevacizumab arm, no difference in PFS were seen (10.3 months versus 10.5 months, logrank p=0.85; HR 1.03 (0.77-138)). rs895374 was neither associated with tumor response nor with median overall survival. Conclusions: The predictive value of rs895374 for cetuximab treatment could be validated and no prognostic value could be established. This is the first report proving that germline polymorphisms in the degradation process predict efficacy of cetuximab in patients with metastatic colorectal cancer. As the process of EGFR recycling is an important mechanism of cetuximab resistance, novel anti-EGFR antibodies like Sym004 may overcome resistance mechanisms by preventing EGFR recycling.