The goal of this proposal is to identify how the composition of the gut microbiome and diet interact to impact chemotherapy-induced diarrhea incidence and severity.

In this longitudinal observational study patients will supply samples of their gut microbiome prior to scheduled colonoscopy or surgery along with dietary intake and blood samples; the relative abundance of microbes from those samples along with dietary data will be used to predict the presence or absence and severity of chemotherapy-induced diarrhea. Microbiome and diet based predictions from blinded samples will be combined to map the diet-microbiome changes during treatment to the changes in immune markers and risk of chemotherapy-induced diarrhea.

Inclusion Criteria:

• Colon cancer diagnosis
• Age >18 and < or equal to 79.
• Ability to perform informed consent
• FOLFOX treatment expected

Exclusion Criteria:

• Not Pregnant
• Does not have Lynch syndrome or FAP diagnosis.
• Inability to perform inform consent
• inability to comply with follow up program
• history of prior colon cancer diagnosis
• previous treatment with antibiotics in the last month.
• previous bowel resection.

Colon cancer patient, prior to surgery or prior to treatment start