The MA-PPING is a multicenter prospective observational study that includes patients undergoing surgery for gastrointestinal cancer.

The study aims to map the oral and gut microbiome of patients diagnosed with pancreatic, esophageal or colorectal cancer during their surgical patient journey from the moment of diagnosis until full recovery (three months after surgery).

Rationale: The gut microbiome is the composition of micro-organisms that reside in the gastrointestinal tract. Under normal circumstances, the microbiome is balanced and has a beneficial effect on gut function. However, when the microbiome is stressed i.e. by an operation, patients' health or medication, the composition of the microbiome may change rapidly and the virulence of its micro-organisms can increase fast. Surgery, in particular gastrointestinal surgery, has a disruptive effect on the mucosal gut barrier and may lead to shifts in microbial composition. Also, the underlying surgical disease itself can be characterized by changes in the microbiome. Gastrointestinal cancer is associated with specified alterations of the microbiome, and the presence of certain microbiota is related with carcinogenesis and lymph node involvement.

Anastomotic leakage is a severe complication after gastrointestinal surgery and several animal studies linked microbial shifts to the development of anastomotic leakage. Only a few, small and explorative, human studies investigated the microbiome during surgery and correlated their findings with the development of postoperative complications. However, the majority of these studies only sampled the microbiome intraoperatively. Surgery-related microbial shifts manifest also in the pre- and postoperative phase, therefore, sampling in these phases is crucial. To further understand the changes of the microbiome composition due to gastrointestinal surgery and the relation with postoperative infectious complications, samples should be collected on several time points; before, during, and after surgery. With this study we aim to map the oral and gut microbiome of patients diagnosed with pancreatic, esophageal or colorectal cancer in a time frame ranging from the work-up for an operation until the postoperative phase to assess the changing composition of the microbiome during a surgical patient journey.

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

All adult patients who are presented/present at the participating hospitals with a proven gastrointestinal malignancy and scheduled for surgery.