More than 2 surgical resections of metastases from colorectal cancer;

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.

"Cancersensor" Chemotherapy