1. Department of Radiotherapy, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands;
2. Radiotherapiegroep, Deventer, The Netherlands;
3. Department of Radiotherapy, Antoni van Leeuwenhoek ziekenhuis, Netherlands Cancer Institute, Amsterdam, The Netherlands;
4. Department of Radiotherapy, Erasmus MC Cancer Institute, Rotterdam, The Netherlands;
5. Radiotherapeutisch Instituut Friesland, Leeuwarden, The Netherlands;
6. Radiotherapiegroep, Arnhem, The Netherlands;
7. Instituut Verbeeten, Tilburg, The Netherlands;
8. Department of Radiotherapy, RadboudUMC, Nijmegen, The Netherlands;
9. MAASTRO Clinic Maastricht, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands;
10. Department of Radiotherapy, HaaglandenMC, The Hague, The Netherlands;
11. Department of Radiotherapy, Isala kliniek, Zwolle, The Netherlands;
12. Department of Radiotherapy, Catharina ziekenhuis, Eindhoven, The Netherlands;
13. Zuidwest Radiotherapeutisch Instituut, Vlissingen and Roosendaal, The Netherlands;
14. Department of Radiotherapy, Leids University Medical Centre, Leiden, The Netherlands;
15. Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands