[1] Kings Coll London, Surg Care Sci, London, England
[2] Kings Coll London, Dept Mol Med & Surg, Upper Gastrointestinal Surg, London, England
[3] Kings Coll London, Div Canc Studies, Sect Gastrointestinal Canc, London, England
[4] Guys & St Thomas NHS Fdn Trust, Upper Gastrointestinal Surg, London, England
[5] Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden
[6] Uppsala Univ, Dept Publ Hlth & Caring Sci, Clin Psychol Healthcare, Uppsala, Sweden