Individualized Dose Escalation of 5-FU for Gastrointestinal Cancer

Inclusion Criteria: Age ≥ 18 years Diagnosis of metastatic or locally advanced/inoperable colorectal cancer or non-colorectal gastrointestinal cancer (including cancers of the stomach, esophagus, appendix, small bowel, and ampulla) Clinically appropriate staging imaging of the chest, abdomen, and pelvis performed within 30 days prior to registration ECOG Performance Status: 0-1 Exclusion Criteria: Any prior receipt of oxaliplatin or fluoropyrimidine chemotherapy (other than radiation-sensitizing fluoropyrimidine chemotherapy) Prior receipt of systemic chemotherapy in the 6 months prior to Day 1 of Cycle 1 of FOX (other than radiation-sensitizing chemotherapy) Known mismatch repair deficiency or microsatellite instability-high disease Known dihydropyrimidine dehydrogenase (DPD) deficiency, as identified by clinically indicated screening Any confirmed second malignancy that is likely to require systemic therapy during the course of the six-month study period, in the opinion of the enrolling investigator Any of the following baseline laboratory abnormalities: Absolute neutrophil count (ANC) < 2,500/mm3 Platelet count < 100,000/mm3 Hemoglobin < 9 g/dL Creatinine > 1.5 x ULN Total bilirubin > 1.5 x ULN AST/ALT > 5 x ULN Patients who are unable to provide informed consent Patients who are pregnant or breastfeeding Patients who are incarcerated, homeless, or have active substance use disorders