[1] St James Univ Hosp, Leeds Gastroenterol Inst, Leeds LS9 7TF, W Yorkshire, England
[2] Univ Leeds, Leeds Inst Mol Med, Leeds, W Yorkshire, England
[3] Univ Leeds, Sch Med, Ctr Biostat & Epidemiol, Leeds LS2 9JT, W Yorkshire, England
[4] Int Agcy Res Canc, Canc Informat Sect, F-69372 Lyon, France
[5] McMaster Univ, Hlth Sci Ctr, Div Gastroenterol, Hamilton, ON, Canada