 The phase I study of Regorafenib in advanced colorectal cancer showed a pronounced interindividual variability of drug exposition. Furthermore, the CORRECT study shows a large pharmacological variability of plasma concentration for Regorafenib and its metabolites. In this study, we propose to explore the pharmacological variability and his potential heritability by the therapeutic drug monitoring of Regorafenib. The objective is to understand and to control the pharmacological variability of Regorafenib and finally to predict the therapeutic response or the toxicity, especially in a population of patients with biliary tract cancer. 