To prospectively evaluate the efficacy and safety of DPYD-guided dosing strategies in a real-world clinical setting, specifically by comparing the incidence of severe (Grade 3 and 4) fluoropyrimidine-related toxicities of heterozygous DPYD variant patients assigned to DPYD-guided reduced dosing versus patients with standard dosing in the control arm.
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.
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.
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