Eligible patients who agree to participate will migrate from oral opioids to transdermal patches and be followed for four weeks. Oral morphine will be provided as pain rescue medication. The patients will inform the adverse events and rescue medication consumption. The number of Fentanest® patches will be adjusted every visit aiming to reduce the rescue medication consumption and adverse events to a minimum. The WHO-QOL- bref (quality of life questionary) will be filled before and after the use of Fentanest®. Patients showing benefit are eligible to a 3 weeks compassionate study.