The standard treatment of metastatic colorectal cancer is based on systemic chemotherapy. Several effective drugs are currently available and can be administered either sequentially or in combination. Most patients receive 2 or 3 lines of chemotherapy. The aim of this randomized trial is to evaluate the potential benefit of a bitherapy with 5-fluorouracil (5-FU) and oxaliplatin as first line chemotherapy compared with a sequential chemotherapy with 5-FU alone as first line chemotherapy followed by the combination of 5-FU with oxaliplatin in case of progressive disease, in terms of progression-free survival and overall survival in patients with advanced colorectal cancer.