Treatment of metastatic colorectal cancer needs chemotherapy in most of the cases. During these last years, many new chemotherapies and targeted therapies have been developed improving significantly the overall survival of patients. However, the choice of the therapeutic sequences becomes difficult due to the lack of validated predictive biomarkers of their efficiency. Indeed, only the mutation of the k-ras oncogene is a predictive factor of non-efficacy of the anti-EGFR antibodies. It is thus crucial to identify new biomarkers to propose the best personalized 1rst line therapeutic sequence. One idea would be to enumerate and characterize the circulating tumor cells (CTC) which, as it has been described in a recent study realized by Cohen et al. in patients with metastatic colorectal cancer, would give us an early evaluation of the therapeutic efficiency. In this context, the investigators have developed an innovative technology, the EPISPOT assay (patent of the University Medical Center of Montpellier), that allows the detection & characterization of viable CTC in the peripheral blood. The EPISPOT technology has been already evaluated in the breast and prostate cancer. Thus, the investigators would like to perform a prospective study on a cohort of patients with metastatic colorectal cancer to confirm, with this technology, the predictive value of CTC count for the efficacy of the treatment.

In the aim to study a homogeneous cohort of patients, the investigators will only recruit patients in first line of treatment and treated by 5-FU (IV), IRINOTECAN et BEVACIZUMAB combination.

Inclusion Criteria:

• Age > 18 years
• Colon or rectum adenocarcinoma (based on the histology)
• Visceral metastases (synchronous and/or metachronous)
• Metastatic disease measurable with the RECIST 1.1 criteria
• WHO performance status 0, 1 or 2
• Life expectancy>3 months when starting the treatment
• Chemotherapy in metastatic 1rst line combining a protocol of conventional chemotherapy combining 5-FU and IRINOTECAN (FOLFIRI, XELIRI) associated with bevacizumab
• Follow-up of at least one year
• Collection of the written consent
• Social security affiliation

Exclusion Criteria:

• 2nd line chemotherapy and beyond
• History of other cancers considered not cured
• Active and progressive infection or other serious disease that may not allow the patient to receive the treatment
• refusal to participate
• Patient unable to express his consent
• Pregnant women
• Patient unable to be followed-up for at least one year
• Current participation to another clinical trial
• Patients under guardianship
• Vulnerable people protected by the law