Dose Individualization of Chemotherapy in Patients With Gastrointestinal Cancers Lacking a Specific Liver Enzyme

Inclusion criteria

• Patients with pre-treatment screening based on \[U\] value according to INCa/HAS recommendations.
• Eastern Cooperative Oncology Group performance status (ECOG PS) ≤2
• Fluoropyrimidine-naïve patients with gastrointestinal cancer starting chemotherapy combining fluoropyrimidine (5-FU or capecitabine) and oxaliplatin whatever the context (adjuvant, neoadjuvant, palliative) including the following regimens (the most frequently prescribed in gastrointestinal cancers):
• biweekly 5-FU and oxaliplatin (FOLFOX) +/- targeted therapy (TT)
• three-weekly capecitabine and oxaliplatin (CAPOX) +/- TT
• Age ≥ 18 years
• Patients eligible for full standard fluoropyrimidine and oxaliplatin doses regardless of DPD deficiency
• Adequate bone marrow function (cell blood count (CBC)), estimated glomerular filtration rate (DFG) ≥ 50 ml/min, alkaline phosphatase (ALP) / aspartate aminotransferase (ASAT) / alanine aminotransferase (ALAT) ≤ 5 upper limit of normal (ULN), and bilirubin ≤ 50 micromol/L
• Patient must have signed and dated a written informed consent form prior to any trial specific procedures. When the patient is physically unable to give their written consent, a trusted person of their choice, independent from the investigator or the sponsor, can confirm in writing the patient's consent.
• Women of childbearing potential must have a negative serum or urine pregnancy test.
• Patients must agree to remain abstinent or use contraceptive methods with a failure rate of \< 1% per year for the duration of study treatment and within 6 months after completing treatment.
• Patients must be affiliated to a Social Security System (or equivalent).
• Patient is willing and able to comply with the protocol for the duration of the trial including undergoing treatment and scheduled visits, and examinations including follow-up.

Exclusion criteria

• Patients with complete DPD deficiency based on \[U\] ≥150 ng/mL
• Any prior treatment including a fluoropyrimidine
• Patients with any contraindication to treatment with fluoropyrimidine or oxaliplatin regardless of DPD deficiency
• Patients not eligible for full standard dose fluoropyrimidine and oxaliplatin for clinical reasons including older age and/or comorbidity regardless of a DPD deficiency
• Patients unwilling or unable to comply with trial obligations for geographic, social, or physical reasons, or who are unable to understand the purpose and procedures of the trial
• Recent or concomitant treatment with brivudine
• Pregnant or breastfeeding woman.
• Participation in another therapeutic trial within 30 days prior to inclusion.
• Persons deprived of their liberty or under protective custody or guardianship.