 Aim of this study is to compare the efficacy and safety of two different sequences of chemotherapeutic agents in order to optimize the treatment of patients with metastatic colorectal cancer progressed to a first line chemotherapy with FOLFIRI and bevacizumab. Primary endpoint will be overall survival, defined as the time elapsed from the date of randomization to the date of patient death due to any cause, or the last date the patient was known to be alive. 