DPYD Pharmacogenomics and Fluoropyrimidine (FP) Dose-Adjustment

Inclusion Criteria: * Diagnosis of cancer in either the adjuvant or metastatic setting requiring initial therapy with 5-FU or Capecitabine. * DPYD testing performed by a CLIA-certified laboratory (i.e., Guardant 360 or Caris blood testing for genomic profiling, DPYD testing by the Mayo Clinic or other certified laboratory) with results available before starting chemotherapy. * DPYD testing results falling into one of the following cohorts for first-line therapy with a fluoropyridine: * Study Cohort: Patients with one DPYD variant in one gene (heterozygotes). * Control Arm: Patients with normal or wild-type DPYD genes, for comparison, will be treated at the usual 100% dose. --FOLFOX regimen (N=50) * ECOG Performance Status 0-2. * Measurable disease or non-measurable disease allowed, including adjuvant 5-FU-based regimens. Exclusion Criteria: * Patients for whom 5-FU or Capecitabine therapy is contraindicated or not deemed appropriate in the judgment of the treating physician. * Patients with two DPYD variants (homozygous deletions or non-functional genetic variants, or double heterozygotes with two different abnormalities) should not receive 5-FU or Capecitabine and are therefore excluded from the study. * Pregnant Women and Children