1. Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands;
2. Department of Radiation Oncology, CHUM, Montreal, QC, Canada;
3. Brigham and Women’s Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts, USA;
4. Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA;
5. Department of Radiation Oncology, Catharina Hospital, Eindhoven, The Netherlands;
6. Department of Radiation Oncology, HagaZiekenhuis, Den Haag, The Netherlands;
7. Department of Radiotherapy, Cancer Center Amsterdam, VU University medical center, Amsterdam, The Netherlands;
8. Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, Alabama, USA;
9. Department of Radiation Oncology, University Hospital Zürich, Zürich, Switzerland;
10. Department of Radiation Oncology, Erasmus MC, Rotterdam, The Netherlands;
11. Holland Proton Therapy Center, Delft, The Netherlands