1. Department of Radiation Physics, Skane University Hospital, Lund, Sweden
2. Department of Oncology, Rigshospitalet, Copenhagen, Denmark
3. Leeds Institute of Medical Research at St James's, University of Leeds and Leeds Cancer Centre, St James's University Hospital, Leeds, United Kingdom
4. Department of Radiation Oncology, University of Maryland Medical Center, Baltimore, MD, USA
5. Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, USA
6. Department of Radiotherapy, University of Groningen, Groningen, The Netherlands
7. Division of Biostatistics and Bioinformatics, University of Maryland Greenebaum Cancer Center, and Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, USA