1. Department of Medicine, Sørlandet Hospital Kristiansand, Kristiansand, Norway
2. Institute of Health and Society, Clinical Effectiveness Research Group, University of Oslo, Oslo, Norway
3. Department of Transplantation Medicine and K. G. Jebsen Colorectal Cancer Research Center, Oslo University Hospital, Oslo, Norway
4. Department of research, Telemark Hospital, Skien, Norway
5. Cancer Registry of Norway, Oslo, Norway
6. Frontier Science, Boston, Massachusetts, United States