Microbiome Analysis in esoPhageal, PancreatIc and Colorectal CaNcer Patients Undergoing Gastrointestinal Surgery

Inclusion Criteria: * Patients with proven malignancy of the distal esophagus, pancreatic head/corpus, colon or rectum * Patients undergoing primary elective surgery with construction of an anastomosis of the gastrointestinal tract * Adult patients above age 18 years * Written informed consent Exclusion Criteria: * History of chronic gastro-intestinal disease e.g. Crohns disease and ulcerative colitis * Presence of acute gastrointestinal infection * Chronic use of oral antibiotics (3 months or longer) * Patients undergoing gastrointestinal surgery for gastrointestinal cancer in acute setting * Patients undergoing construction of an end/loop colostomy or ileostomy (following primary resection) * Patients undergoing colon and/ or rectal resection without construction of an anastomosis * Patients who have insufficient knowledge of the Dutch language * Patients who are not able to give reliable answers to the questionnaires due to a (mental) disease or (cognitive) condition * Patients who are not able to collect microbiome samples due to a physical or mental condition