Individualized Dose Escalation of 5-FU for Gastrointestinal Cancer

This is a single-arm clinical trial that will evaluate the feasibility of a chemotherapy regimen adaptive, individualized dose escalation of 5-FU chemotherapy for patients who have good tolerance of the initial dose. Study participants will also receive oxaliplatin chemotherapy together with 5-FU, at standard doses. The goal of the study is to examine the feasibility and effectiveness of this approach, using individualized dose escalation of 5-FU in patients who do not have serious side effects at lower doses.