1. From the Division of Cancer and Stem Cells, University of Nottingham, School of Medicine, City Hospital Campus, Hucknall Road, Nottingham NG5 1PB, England (Y.C.); Nottingham Breast Institute, Nottingham University Hospitals NHS Trust, Nottingham, England (J.J.J.); Department of Radiology, Cheltenham General Hospital, Cheltenham, England (E.J.C.); and Young Person and Adult Screening Programmes, Public Health England, Sheffield, England (J.J.).