[1] Univ Nottingham, Div Primary Care, Sch Community Hlth Sci, Nottingham NG7 2RD, England
[2] Univ Leeds, Ctr Canc Res, Leeds LS2 9JT, W Yorkshire, England
[3] Univ Nottingham, Sch Community Hlth Sci, Div Epidemiol & Publ Hlth, Nottingham NG7 2RD, England
[4] Radcliffe Infirm, Canc Res UK Epidemiol Unit, Oxford OX2 6HE, England
[5] Univ So Calif, Keck Sch Med, Dept Prevent Med, Los Angeles, CA 90033 USA
[6] Royal London Hosp, Dept Med Oncol, London, England