1 KU Leuven - University of Leuven, University Hospitals Leuven, Department of Radiation Oncology, B-3000 Leuven, Belgium. Electronic address: daan.nevens@uzleuven.be.
2 University of Ghent-University Hospital of Ghent, Department of Radiation Oncology, B-9000 Leuven, Belgium.
3 University of Ghent-University Hospital of Ghent, Department of Otorhinolaryngology, Head and Neck Surgery, B-9000 Leuven, Belgium.
4 Leuven Biostatistics and Statistical Bioinformatics Centre, University of Leuven, B-3000 Leuven, Belgium.
5 KU Leuven - University of Leuven, University Hospitals Leuven, Department of Radiation Oncology, B-3000 Leuven, Belgium.