1. Imperial College London, London, United Kingdom
2. Gloucestershire Royal Hospital, Gloucester, United Kingdom
3. Erasmus MC University Medical Centre, Rotterdam, the Netherlands
4. Telemark Hospital, 3710 Skien, Norway
5. CPO Piemonte and S. Giovanni University Hospital, Turin. Italy
6. Hospital General Universitario de Alicante, Alicante, Spain
7. Knappschafts Hospital, Ruhr University of Bochum, Bochum, Germany
8. Screening Group, Early Detection and Prevention Section, International Agency for Research on Cancer, Lyon, France