1. Center for Cancer Treatment, Sørlandet Hospital, Kristiansand, Norway;
2. Department of Obstetrics and Gynecology, Sørlandet Hospital, Kristiansand, Norway;
3. Department of Oncology, Innlandet Hospital, Gjøvik, Norway;
4. Department of Oncology, Oslo University Hospital, Oslo, Norway;
5. Department of Oncology, Stavanger University Hospital, Stavanger, Norway;
6. Department of Public Health and General Practice, Norwegian University of Science and Technology, Trondheim and the Norwegian Institute of Public Health, Oslo, Norway;
7. K. G. Jebsen Colorectal Cancer Research Centre, Oslo University Hospital, Oslo, Norway