1 Clinical Effectiveness Research Group, University of Oslo and Oslo University Hospital, 0318 Oslo, Norway. Electronic address: michael.bretthauer@medisin.uio.no.
2 Clinical Effectiveness Research Group, University of Oslo and Oslo University Hospital, 0318 Oslo, Norway; Department of Gastroenterological Oncology, Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Warsaw, Poland.