1. Department of General, Visceral and Paediatric Surgery, University Medical Centre Göttingen, Göttingen, Germany
2. Department of Medical Statistics, University Medical Centre Göttingen, Göttingen, Germany
3. Department of Radiotherapy, University Medical Centre Erlangen, Erlangen, Germany
4. Department of Surgery, Krankenhaus der Barmherzigen Brüder, St Veit an der Glan, Austria
5. Department of Surgery, University Medical Centre Erlangen, Erlangen, Germany
6. Department of General and Visceral Surgery, Klinikum Esslingen, Esslingen, Germany
7. University Department of General and Visceral Surgery, Klinikum Oldenburg, Oldenburg, Germany
8. Department of Radiotherapy and Oncology, University Medical Centre Frankfurt, Frankfurt/Main, Germany