1. From the Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792-3252 (E.S.B.); Centre for Cancer Prevention, Queen Mary University of London, Wolfson Institute of Preventive Medicine, London, England (D.V., S.W.D.); and Nuffield Department of Population Health, University of Oxford, Oxford, England (R.G.B.).