TAS-102 With or Without Celecoxib in ctDNA-defined Minimal Residual Disease in Colorectal Cancer After Completion of Adjuvant Chemotherapy

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.

Inclusion Criteria: 1. Has histological confirmation of colorectal cancer 2. Received post-R0 resection of stages II, III, or IV colorectal cancer and has completed all planned curative intent therapies that must include ≥ 3 months of oxaliplatin containing chemotherapy 3. Has no definitive evidence of radiographic disease per assessment by investigators within 28 days (before or after) a positive ctDNA assay 4. Has minimal residual disease as defined by positive ctDNA assay (completed as standard-of-care at MD Anderson). Patients may be identified for enrollment with any Clinical Laboratory Improvement Amendments (CLIA)-certified ctDNA assay for MRD. MRD status will be confirmed with the Signatera assay prior to initiation of therapy (unless the prior testing was also done with Signatera in which case this test would not require confirmation) 5. Has adequate organ and marrow function as defined below: 1. absolute neutrophil count: ≥1,000/mcL 2. platelets: ≥100,000/mcL 3. total bilirubin: ≤ institutional upper limit of normal (ULN) 4. AST(SGOT)/ALT(SGPT): ≤3 × institutional ULN 5. Serum creatinine ≤ 1.5 × ULN or creatinine clearance ≥60 mL/min. Creatinine clearance (Clcr) can either be measured in a 24-hour urine collection or estimated by the Cockcroft-Gault equation as follows: Clcr (mL/min) = \[(140 - age) x (weight in kg) ÷ \[72 x (serum creatinine in mg/dL)\] \[0.85 if female\] 6. Has ECOG performance status (PS) of 0 or 1 7. Is of age ≥ 18 years. Because no dosing or adverse-event data are currently available on the use of TAS-102 in patients, children \