Gut Microbiome in Colorectal Cancer

This is a pilot feasibility study designed to investigate the alterations in the gut microbiome that occur during the course of treatment for colorectal cancer (CRC). Three patient cohorts will be followed. Cohort A: patients treated with oral fluoropyrimidine CAP as part of standard of care (SOC) chemotherapy. Cohort B: patients treated with TAS-102 including those receiving it in combination with Y-90 radioembolization as part of a clinical trial. Cohort C: patients receiving CAP plus immunotherapy (pembrolizumab) and bevacizumab as part of a clinical trial. Investigators will replace participants as needed to ensure a minimum of 10 evaluable participants per cohort (or minimum total of 30 evaluable patients). Evaluable participants are defined as patients with two analyzable stool samples including a baseline sample and at least one on-treatment sample to be used in endpoint analysis