1. Department of Oncology and Palliative Medicine, Nordland Hospital, 8092 Bodø, Norway
2. Institute of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, 9038 Tromsø, Norway
3. Department of Radiation Oncology, University Hospital Freiburg, 79106 Freiburg, Germany
4. Department of Radiation Oncology, Northwestern University, Chicago, IL 60611, USA