<qa>  What is the dose modification required to do?Patients will be followed during 12 months with 5 visits: Week 4, Week 8, Week 16, Month 6 and Month 12. Adverse event related to sorafenib will be recorded and graded according to the NCI-CTC for Adverse Event during all the study period. Sorafenib plasma concentrations will be assessed at 4, 8 and 16 weeks. An additional dosage could be performed between W1 and W4, before dose modification, if a dose modification is necessary due to adverse events before W4. 