1. Department of Radiation Oncology, University of Lubeck, 23562 Lubeck, Germany
2. Department of Oto-Rhino-Laryngology & Head and Neck Surgery, University of Lubeck, 23562 Lubeck, Germany
3. Department of Oral and Maxillofacial Surgery, University of Lubeck, 23562 Lubeck, Germany
4. Department of Oral and Maxillofacial Surgery, MSH Medical School Hamburg, Schwerin Campus, 19055 Schwerin, Germany
5. Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, USA