Impact of CES1 Genotype on Capecitabine Exposure in Cancer Patients

Launched by ERASMUS MEDICAL CENTER · Aug 4, 2025

Keywords

ClinConnect Summary

This clinical trial is studying how a person's genetic makeup affects the way their body handles a cancer drug called capecitabine, which is commonly used to treat cancers of the stomach, esophagus, colon, and breast. Capecitabine works by turning into an active substance in the body that fights cancer, but this process depends on certain liver enzymes—especially one called CES1. Some people have a version of this enzyme that doesn’t work as well, which might cause the drug to stay in the body longer and increase the chance of side effects like hand-foot syndrome, where the hands and feet become red and painful. This study aims to see if patients with less active CES1 have higher levels of the active drug in their blood and if they experience more side effects.

To take part, you need to be 18 or older and about to start treatment with capecitabine combined with another drug called oxaliplatin, as part of your usual cancer care. You should be healthy enough for this treatment and able to understand and follow the study’s instructions. People who have certain genetic conditions, previous treatments with similar drugs, or specific medical issues that affect drug absorption cannot join. If you participate, the researchers will monitor your blood to measure drug levels and watch for side effects. The goal is to learn how to better tailor treatments in the future to reduce side effects and improve care for patients like you.

Gender

ALL

Eligibility criteria

• In order to be eligible to participate in this study, a subject must meet all of the following criteria:
• • 18 years of age or older;
• • Planned to start treatment with concomitant capecitabine and oxaliplatin according to standard of care (irrespective of dose);
• • Fit for treatment with capecitabine and oxaliplatin as judged by the treating physician;
• • Capable of understanding and complying with protocol requirements and able to understand and sign the informed consent form.
• Exclusion Criteria:
• A potential subject who meets any of the following criteria will be excluded from participation in this study:
• • Carrier of a known clinically relevant DPYD variant (i.e. \*2A, \*7, \*13, c.1236G\>A or c.2846A\>T);
• • Any medical condition that is known to influence capecitabine absorption (i.e. a Roux-en-Y gastric bypass operation or complete gastric resection; an esophagectomy is not considered to impair absorption);
• • Prior treatment with fluoropyrimidines;
• • Use of DPD-inhibitors and/or allopurinol;
• • Known pregnancy at baseline.