1. Department of Oncology and Palliative Medicine, Nordland Hospital Trust, Bodø, Norway;
2. Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway;
3. Department of Radiation Oncology, University Medical Centre Groningen, Groningen, Netherlands;
4. Department of Radiation Oncology, University Hospital Zürich, Zürich, Switzerland;
5. Department of Radiation Oncology, University Hospital Freiburg, Freiburg, Germany;
6. Partner Site Freiburg, German Cancer Consortium (DKTK), Freiburg, Germany