This is a Phase II multi-center exploratory study to identify biomarkers predictive of clinical response to aflibercept in patients with metastatic colorectal cancer who have failed first-line therapy, consisting of an oxaliplatin-containing regimen in combination with bevacizumab. Patients will consent to a needle core biopsy of a liver metastatic lesion prior to starting treatment. This study will be open primarily at sites conducting the Q-CROC-01 study (NCT00984048), in which colorectal cancer patients receiving standard first-line treatment undergo a biopsy of a liver metastatic lesion before treatment and at resistance. The post-first-line treatment biopsy will be used as the pre-treatment biopsy for this trial. For patients not participating in the Q-CROC-01 study, patients will be required to undergo a liver needle core biopsy of a metastatic lesion before study treatment.