1. Department of Surgery, Leiden University Medical Center, Leiden, The Netherlands
2. Department of Radiotherapy, the Netherlands Cancer Institute—Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
3. Department of Surgery, the Netherlands Cancer Institute—Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
4. Department of Surgery, The Royal Marsden NHS Foundation Trust, London, UK
5. Department of Surgery, Lund University Hospital, Lund, Sweden
6. Department of Surgery, Aarhus University Hospital, Aarhus, Denmark
7. Department of Medical Statistics, Leiden University Medical Center, Leiden, The Netherlands
8. King's College London, Thames Cancer Registry, London, UK
9. Comprehensive Cancer Centre South, Eindhoven, The Netherlands