1. Department of Oncological Gastroenterology, Maria Sklodowska-Curie National Research Institute of Oncology, 02-781 Warsaw, Poland
2. Department of Gastroenterology, Hepatology and Clinical Oncology, Centre of Postgraduate Medical Education, 02-781 Warsaw, Poland
3. Department of Gastroenterology, Hepatology and Infectious Diseases, Otto-von-Guericke University, 39120 Magdeburg, Germany