[1] Royal Marsden Hosp, Canc Res Campaign, Med Sect, Sutton SM2 5PT, Surrey, England
[2] Royal Marsden Hosp, Canc Res Campaign, Gastrointestinal Unit, Sutton SM2 5PT, Surrey, England
[3] Inst Canc Res, Sutton SM2 5PT, Surrey, England
[4] Christie Hosp NHS Trust, CRC Dept Med Oncol, Manchester M20 4BX, Lancs, England
[5] Guys Hosp, Dept Med Oncol, London SE1 9RT, England
[6] St James Univ Hosp, Imperial Canc Res Fund, Canc Med Res Unit, Leeds LS9 7TF, W Yorkshire, England
[7] Univ Glasgow, CRC Dept Med Oncol, Glasgow G61 1BD, Lanark, Scotland
[8] St Georges Hosp, Dept Med Oncol, London SW17 0QT, England