1 Department of Oncological Gastroenterology, National Research Institute of Oncology, Warsaw, Poland; Medical Center for Postgraduate Education, Warsaw, Poland; Clinical Effectiveness Research Group, University of Oslo, Oslo, Norway. Electronic address: mfkaminski@coi.waw.pl.
2 Department of Oncological Gastroenterology, The Maria Sklodowska-Curie National Research Institute of Oncology, Warsaw, Poland; Medical Center for Postgraduate Education, Warsaw, Poland; Clinical Effectiveness Research Group, University of Oslo, Oslo, Norway.