[1] Gen Infirm, Dept Surg, Leeds LS1 3EX, W Yorkshire, England
[2] Univ Birmingham, W Midlands Canc Intelligence Unit, Birmingham B15 2TT, W Midlands, England
[3] Gen Infirm, Dept Clin Oncol, Leeds LS1 3EX, W Yorkshire, England
[4] St James Univ Hosp, Dept Acute Med, Leeds LS9 7TF, W Yorkshire, England
[5] Univ Leeds, Ctr Biostat & Epidemiol, Leeds LS16 6BQ, W Yorkshire, England
[6] No & Yorkshire Canc Registry & Informat Serv, Leeds LS16 6BQ, W Yorkshire, England