1. Department of Surgical Oncology; University of Groningen; University Medical Center Groningen; Groningen The Netherlands
2. Department of Colorectal Surgery; Hospital Universitari Vall d'Hebron; Universitat Autonoma de Barcelona; Barcelona Spain
3. Department of Epidemiology; University of Groningen; University Medical Center Groningen; Groningen The Netherlands
4. Department of Surgery; Zaandam Medical Centre; Zaandam The Netherlands
5. Royal North Shore Hospital; Sydney New South Wales Australia