1. Center for Research and Development, Uppsala University/County Council of Gävleborg, Gävle Hospital, Gävle, Sweden;
2. Department of Radiation Sciences and Oncology, Umeå University Hospital, Umeå, Sweden;
3. Department of Radiology, Gävle Hospital, Gävle, Sweden;
4. EpiStat, Uppsala, Sweden;
5. Department of Oncology, Gävle Hospital, Gävle, Sweden;
6. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden;
7. Regional Cancer Center Uppsala-Örebro, Uppsala, Sweden