1. Department of Oncology, Oslo University Hospital, Norwegian Radium Hospital, 0424 Oslo, Norway
2. The Norwegian Cancer Registry, 0304 Oslo, Norway
3. Department of Oncology, Haukeland University Hospital, 5020 Bergen, Norway
4. Oslo Center for Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, 0424 Oslo, Norway
5. Department of Orthopedics, Oslo University Hospital, Norwegian Radium Hospital, 0424 Oslo, Norway
6. Institute of Clinical Medicine, University of Oslo, 0318 Oslo, Norway