Primary Objectives:~The primary objective is to determine the 6-month ctDNA clearance rate in colorectal cancer patients with minimal residual disease following 6 months of TAS-102 therapy.~Secondary Objectives:~To determine the 3-month ctDNA clearance rate in colorectal cancer patients with minimal residual disease.~To determine the disease free survival (DFS) amongst colorectal cancer patients with minimal residual disease following 6 months of TAS-102 therapy.~To determine the overall survival (OS) amongst colorectal cancer patients with minimal residual disease following 6 months of TAS-102 therapy.~To determine the safety and tolerability of TAS-102 for the treatment of colorectal cancer patients with minimal residual disease.~Exploratory Objectives:~To determine markers of response and resistance in archival tumor tissue including but not limited to immune profiles of tumor-infiltrating lymphocytes, expression of immune markers in tumor cells and microenvironment, and molecular markers (including but not limited to mutations, deletions, and/or amplifications or cancer molecular subtype)~To determine changes in profiles of circulating lymphocytes and ctDNA with treatment~To determine baseline characteristics in archival tumor and/or plasma that may predict clinical benefit
To measure the level of circulating tumor DNA (ctDNA) in the blood of colorectal cancer patients after 6 months of receiving TAS-102 therapy. ctDNA is genetic material from tumor cells that can be found and measured in the blood.