1. Cancer Research UK Centre for Epidemiology, Mathematics and Statistics, Wolfson Institute of Preventive Medicine, Charterhouse Square, London EC1M 6BQ, UK
2. School of Health and Related Research (ScHARR), The University of Sheffield, 30 Regent Street, Sheffield S1 4DA, UK
3. NHS Cancer Screening Programmes, Fulwood House, Old Fulwood Road, Sheffield S10 3TH, UK