1 Gastrointestinal Oncology Service & Cancer of Unknown Primary Service, University College London Hospital NHS Foundation Trust, London, UK.
2 MRC CTU UCL, London, UK.
3 Gastrointestinal Oncology Service & Cancer of Unknown Primary Service, University College London Hospital NHS Foundation Trust, London, UK. khurum.khan1@nhs.net.
4 UCL Cancer Institute, London, UK. khurum.khan1@nhs.net.
5 North Middlesex University Hospital, London, UK. khurum.khan1@nhs.net.