[1] London Sch Hyg & Trop Med, Dept Noncommunicable Dis Epidemiol, Fac Epidemiol & Populat Hlth, Keppel St, London WC1E 7HT, England
[2] Med & Healthcare Prod Regulatory Agcy, Clin Practice Res Datalink CPRD, 10th Floor,10 South Colonnade, London E14 4PU, England
[3] Royal Marsden NHS Fdn Trust, Dept Med, Fulham Rd, London SW3 6JJ, England
[4] Royal Marsden NHS Fdn Trust, Dept Med, Downs Rd, Surrey SM2 5PT, England