Gut Microbiome in Colorectal Cancer

Inclusion Criteria:

1. The patient has histologically proven colorectal adenocarcinoma
2. The patient is starting treatment with oral fluoropyrimidine therapy: CAP or TAS-102 as SOC or on a clinical trial. This also includes those patients receiving treatment in the adjuvant setting or post-metastasectomy with no evidence of disease on imaging.
3. Combination of oral fluoropyrimidine with other cancer-directed therapies, including oxaliplatin, bevacizumab, Y-90 radioembolization, or immunotherapy checkpoint inhibitors, is permitted.
4. Combination of CAP with concurrent radiation is permitted, including patients undergoing radiotherapy to a rectal primary or a metastatic site.
5. Male or female patient aged 18 years of age or older at the time of obtaining the signed and dated informed consent (no upper age limit).
6. Be able to read and speak English.
7. Be willing and able to provide written informed consent for the study

Exclusion Criteria:

1. Patient has had prior chemotherapy, biologic or immunotherapy in the previous 2 weeks.
2. Patient has completed a course of antibiotics longer than 2 weeks in preceding six months or a course of antibiotics of any duration in the 4 weeks prior to starting oral chemotherapy. Any patient who requires treatment with antibiotics during the study may be removed at the investigator's discretion.
3. Known HIV positive.