The first 5 patients will start with dose level 5 mg Lenalidomide and further escalating dose. After the fifth patient is included in the study, enrolment will be interrupted until this patient has finished his first treatment cycle. A safety board will evaluate the toxicities of the first 5 patients. If there are more than 2 patients experiencing a dose limiting toxicity (DLT) in the first treatment cycle, the starting dose will not be escalated and further 5 patients will be enrolled with a starting dose of 5 mg Lenalidomide. If only 2 or less patients experience a DLT in the first treatment cycle, the next 5 patients will start the treatment with 10 mg Lenalidomide.