1. Department of Surgery, Levanger Hospital, Nord-Trøndelag Hospital Trust, Levanger, Norway
2. HUNT Research Centre, Department of Public Health and General Practice, Norwegian University of Science and Technology, Levanger, Norway
3. Upper Gastrointestinal Surgery, Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden
4. Unit for Applied Clinical Research, Institute of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway