1. Department of Radiation Oncology, University of Washington, Seattle, WA, USA
2. Department of Radiation Oncology, School of Medicine, University of Maryland, Baltimore, MD, USA
3. Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München (TUM), München, Germany
4. Department of Radiation Sciences (DRS), Institute of Innovative Radiotherapy (iRT), Helmholtz Zentrum München, Neuherberg, Germany
5. Deutsches Konsortium für Translationale Krebsforschung (DKTK), Partner Site Munich, Heidelberg, Germany
6. Institut Curie, Centre de Protonthérapie d’Orsay, Orsay, France
7. Laboratoire d'Imagerie et Modélisation en Neurobiologie et Cancérologie (IMNC), Centre National de la Recherche Scientifique, Universités Paris 11 and Paris 7, Campus d'Orsay, Orsay, France