1 Department of Radiation Oncology, University Hospital Muenster, Muenster, Germany.
2 Department of Radiation Oncology, University Medical Center Schleswig Holstein, Kiel, Germany.
3 Department of Radiation Oncology, University Medical Center Schleswig Holstein, Kiel, Germany; Department of Radiation Oncology, University Medical Center Groningen and University of Groningen, Groningen, the Netherlands.
4 Department of Radiation Oncology, University Medicine Mannheim, Medical Faculty Mannheim, University Heidelberg, Mannheim, Germany.
5 Department of Radiation Oncology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
6 Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany; Department of Radiation Oncology, University Medical Center Göttingen, Göttingen, Germany.