1. School of Medicine, University of Belgrade, Belgrade, Serbia;
2. Department for Colorectal and Pelvic Surgery, First Surgical Clinic, Clinical Center of Serbia, Belgrade, Serbia;
3. Department for Esophagogastric Surgery, First Surgical Clinic, Clinical Center of Serbia, Belgrade, Serbia;
4. Center for Gastrointestinal Malignancies, MedStar Washington Cancer Institute, MedStar Washington Hospital Center, Washington, DC, USA