How the CES1 liver enzyme affects capecitabine levels in people with colorectal, gastric, or esophageal cancer

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This is an observational study enrolling adults beginning standard capecitabine plus oxaliplatin (CAPOX) to collect blood samples for pharmacokinetic analysis and CES1 genotyping. Researchers will measure capecitabine exposure and its metabolites over time and correlate those levels with CES1 genetic variants. Patients with known clinically relevant DPYD variants or prior fluoropyrimidine treatment are excluded to avoid confounding. The goal is to link CES1 genotype with drug exposure and frequency of toxicities such as hand‑foot syndrome.

Why it matters

Who can join: the full rules

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.

Where it's running

• Erasmus MC Cancer Institute
  Rotterdam, Netherlands Recruiting

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.