Evaluation of Cognitive Function of Patients With Sunitinib or Sorafenib

Patients with advanced kidney cancer or GIST (Gastro Intestinal Stromal Tumor: this is a tumor of the intestines) may be eligible for treatment with one of the following drugs: sunitinib (Sutent ®) or sorafenib (Nexavar ®). These drugs inhibit blood vessel formation in cancer cells. These cancer cells are hampered in their growth. To enlarge the investigators knowledge on the effects and side effects of these two medicines, in the University Medical Center St. Radboud lot of research is done. This study is a part of that. Patients receiving sunitinib or sorafenib tell sometimes that they feel that they are less able to concentrate, that their memory is not working properly or that they are less able to imagine a solution to a complex problem . Perhaps you recognize these symptoms as well. In how many of the patients this occurs, how severe the symptoms are and how it is caused, is still unknown. The goal of this research is to examine how memory, concentration and knowledge processing works in patients using sorafenib or sunitinib. With the research the investigators hope to get answers to the following questions: 1. How common are problems with memory, concentration and processing of knowledge in patients receiving the drug sunitinib or sorafenib? 2. What are the problems of memory, concentration and processing of knowledge in the use of sunitinib or sorafenib? 3. What could be the cause of the problems that patients experience from memory, concentration and processing of knowledge in the use of sunitinib or sorafenib? 4. Is there a link between problems with memory, concentration and processing of knowledge and also experiences of fatigue or mood of a patient?