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