Then, the investigators decided to perform a randomized pharmacokinetic comparative study between biweekly TOMOX (raltitrexed 2 mg/m2 and oxaliplatin 85mg/m2) and triweekly TOMOX (raltitrexed 3 mg/m2 and oxaliplatin 130mg/m2) regimens in metastatic colorectal cancer patients, in a "ping-pong" crossover strategy to reduce the intra-individual variability. Bevacizumab was allowed at the dose of 5mg/kg or 7.5mg/kg, in biweekly and triweekly schedules, respectively. The secondary end-points were, objective response rate evaluated by RECIST 1.1 criteria, PFS, overall survival (OS), toxicity, and the comparison of toxicity between two arms for the first 2 cycles.