1 Gastrointestinal Unit, The Royal Marsden Hospital, London SW3 6JJ, UK; Department of Surgery and Cancer, Imperial College London, London, UK. Electronic address: p.tekkis@imperial.ac.uk.
2 Gastrointestinal Unit, The Royal Marsden Hospital, London SW3 6JJ, UK.
3 Department of Radiology, The Royal Marsden Hospital, London, UK.