It is a prospective, non-randomized, monocentric study. The purpose of the study is to assess the predictive value of VE-cadherin on the objective tumor response.

Biological factors will be correlated to clinical outcome measures.

100 patients treated with bevacizumab for a metastatic colorectal adenocarcinoma will be enrolled.

Patients will be followed every 10 weeks until progression in spite of bevacizumab or until they stop bevacizumab because of toxicity.

Bevacizumab will be administered according to investigators appreciation.

Blood samples will be collected at enrollment, at second bevacizumab's administration and every 10 weeks until progression, or until patients stop bevacizumab because of toxicity or until one year at most in case that patients still receive bevacizumab.

Inclusion Criteria:

• Patient with a metastatic colorectal cancer proved histologically and treated with bevacizumab in first line.
• At least one extra-osseous, non-irradiated, measurable site (>= 10 mm with spiral CT).
• No prior radiotherapy treatment unless treatment is over for at least 4 weeks.
• Adult patients.
• PS <= 2.
• Life expectancy greater than 3 months.
• Mandatory affiliation with a healthy security insurance.
• Signed written informed consent.

Exclusion Criteria:

• Prior chemotherapy for the metastatic cancer.
• Prior bevacizumab treatment.
• Other current cancer or previous cancer detected in the last 5 years that can be linked to the current disease.
• Patient deprived of freedom.
• Pregnant or lactating women.