1. Department of Digestive Surgery, University Hospital of North Norway, Tromsø, Norway
2. Department of Oncology, University Hospital of North Norway, Tromsø, Norway
3. Department of The Cancer Registry of Norway, Oslo, Norway
4. Department of Digestive Surgery, Oslo University Hospital Ullevaal, Oslo, Norway
5. Institute of Clinical Medicine, Faculty of Medicine, University of Tromsø, Tromsø, Norway