Patients with specific genetic mutations in the DPYD-gene have lower activity of the dihydropyrimidine dehydrogenase (DPD) enzyme, which is the rate-limiting enzyme in the metabolism of fluoropyrimidines. Fluoropyrimidines are commonly used as chemotherapeutic drugs and include 5-Fluorouracil, capecitabine, and tegafur. Patients with decreased DPD activity are at higher risk of serious adverse events when treated with standard doses of fluoropyrimidines~This study will examine the clinical implementation of the pre-emptive DPYD-genotype test. The test will analyze four of the most common genetic mutations(SNPs) in the DPYD-gene that leads to significant decreased DPD-activity~In patients with DPYD-variant mutations, the recommended starting dose is 50%. This dose reduction will possibly reduce the rate of serious adverse events. Patients who are homozygous or compound heterozygous for a DPYD-mutation will not be treated with fluoropyrimidines due to the high risk of fatal adverse effects.~Aim To reduce the overall incidence of severe adverse reactions(grade >= 3) to chemotherapy regimens containing 5-FU, capecitabine, or S1 in an unselected population of colorectal, non-colorectal GI cancer, or breast cancer patients through pre-emptive DPYD-genotyping.~Design The investigators will conduct an open clinical trial using historical controls. The investigators will implement pre-emptive genotype testing of about 1000 consecutive patients subject to 5-FU, capecitabine, or S1 treatment for colorectal, non-colorectal GI, or breast cancer. The investigators will use a historical control group of about 500 consecutive similar patients.~Genotype and Phenotype Patients included in the study who are genotyped for DPYD will have blood collected for a post hoc phenotype test. The blood samples will be used to measure levels of uracil.~Some patients in the historic cohort have donated blood to an independent biobank at the time of their cancer treatment. These samples will be used for post hoc DPYD-genotype analysis after the necessary ethical approvals.~Cost-effectiveness An economic analysis will be undertaken to examine if implementing the DPYD-genotype is cost-effective.
The purpose of this study is to examine the benefits of a clinical implementation of a DPYD-genotype test to patients starting treatment with fluoropyrimidines (Fluorouracil (5-FU), capecitabine, tegafur).