Individualized Dose Escalation of 5-FU for Gastrointestinal Cancer

This study is testing whether adjusting the dose of 5-FU (fluorouracil) — a chemotherapy drug — based on blood level monitoring can improve outcomes for people with gastrointestinal cancers. Standard chemotherapy doses are based on body size, but individual metabolism varies. The goal is to personalize dosing to maximize effectiveness and reduce side effects. **You may be eligible if:** - You are 18 years old or older - You have metastatic or locally advanced colorectal cancer, or another gastrointestinal cancer (stomach, esophagus, small bowel, appendix, or ampullary cancers) that cannot be surgically removed - You have had appropriate imaging of the chest, abdomen, and pelvis within the past 30 days - Your general health is good (ECOG performance status 0–1) **You may NOT be eligible if:** - You have previously received oxaliplatin or fluoropyrimidine chemotherapy (other than radiation-sensitizing doses) - You have received systemic chemotherapy in the past 6 months for this cancer Talk to your doctor to see if this trial is right for you.