Genetic Analysis-Guided Dosing of FOLFIRABRAX in Treating Patients With Advanced Gastrointestinal Cancer

Inclusion Criteria: * Histologically or cytologically confirmed locally advanced or metastatic pancreatic adenocarcinoma, gastric adenocarcinoma, cholangiocarcinoma, gall bladder adenocarcinoma, ampullary carcinoma, adenocarcinoma of unclear primary (with a gastrointestinal primary suspected), or other primary gastrointestinal malignancy for which the treating physician feels that FOLFIRABRAX is a reasonable therapeutic option * Patients with a history of obstructive jaundice due to the primary tumor must have a metal biliary stent in place * Eastern Cooperative Oncology Group (ECOG) performance status =\< 1 * Life expectancy \> 3 months * Absolute neutrophil count (ANC) \>= 1500/ul * Hemoglobin \> 9 g/dL * Platelets \> 100,000/ul * Total bilirubin =\< 1.25 times upper limit of normal * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) =\< 2.5 times upper limit of normal * Alkaline phosphatase =\< 2.5 times the upper limit of normal, unless bone metastasis is present in the absence of liver metastasis * Creatinine =\< 1.5 mg/dL * Measurable or non-measurable disease will be allowed, but only those with measurable disease will be evaluable for the response rate endpoint * Women of childbearing potential and sexually active males must use an effective contraception method during treatment and for three months after completing treatment * Negative serum or urine beta human chorionic gonadotropin (beta-hCG) pregnancy test at screening for patients of childbeari…