 This study aims to determine the efficacy of regorafenib as single-agent treatment for the treatment of second-line metastatic colorectal cancer and to identify predictive biomarkers in the actual metastatic tumors to be treated. In the case of metastatic CRC patients, liver lesions are frequently the most common site of metastatic deposit and these lesions can be biopsied to assess putative biomarkers. Patients will be asked to undergo a biopsy of a metastatic lesion prior to treatment, and an optional liver biopsy at the time of relapse. Using several high-throughput discovery platforms, biomarkers will be identified in the metastatic tumor specimens and in blood samples collected throughout the treatment. This will allow us to evaluate putative biomarkers and monitor tumor biomarker dynamics using serial blood collection. 