Inclusion Criteria

Inclusion Criteria for patients:

- Histologically-confirmed metastatic colorectal cancer;

- 0 to 3 prior chemotherapy lines;

- Signed informed consent;

- Good understanding of the protocol and of the follow-up;

- Estimated life expectancy exceeding 3 months;

- At least one measurable metastatic lesion (RECIST criteria);

- Performance Status (WHO) of 0 to 2;

- Good haematological, hepatic and renal functions.

Inclusion criteria for healthy subject

- Age ≥ 18 ans

- Signed informed consent;

- Good understanding of the protocol and of the follow-up;

- Good haematological, hepatic and renal functions.

- Test HIV and B and C hepatitis negative test

- No chronic or acute diseases

Exclusion Criteria for patients:

- Poor performance status (>2);

- Poor haematological, hepatic or renal functions;

- Uncontrolled chronic disease;

- Serious unhealed wound, ulcer or fracture within the previous month;

- Clinical or laboratory finding suggesting possible abnormalities in nucleosides
urinary excretion;

- Pregnancy or breast-feeding during the previous month;

- Transmeridian trip of more than 4 time zones within the prior 2 weeks;

- Person with legal restriction to participate into clinical research, according to the
current law in France.

Exclusion criteria for healthy subject:

- Poor haematological, hepatic or renal functions;

- Uncontrolled chronic disease;

- Serious unhealed wound, ulcer or fracture within the previous month;

- Clinical or laboratory finding suggesting possible abnormalities in nucleosides
urinary excretion;

- Pregnancy or breast-feeding during the previous month;

- Transmeridian trip of more than 4 time zones within the prior 2 weeks;

- Person with legal restriction to participate into clinical research, according to the
current law in France.