The analysis of circulating DNA (Deoxyribonucleic acid) to identify potential resistance mechanisms during anti-EGFR (epidermal growth factor receptor) treatment is of great interest, as evidenced by the recent journal published by Corcoran in the prestigious New England Journal of Medicine.

EmutRAS is one of the first studies that will specifically and prospectively evaluate the RAS mutational switch and its impact on the efficiency of the 1st line processing.

The primary study objective is the Detection of RAS mutational (rat sarcoma viral oncogene homolog) "switch" in circulating DNA by Intplex® test in mCRC (metastatic colorectal cancer) patients treated with antibody anti-EGFR (epidermal growth factor receptor), cetuximab or panitumumab in first line.

The treatment and these modalities will be decided by the investigator.

The study is based on blood sampling, the frequency of which is described below, rhythm of plasma samples:

Inclusion after determination of wild status RAS tissues.

First sampling of 2 EDTA (ethylenediaminetetraacetic acid) tubes, then at each tumour evaluation during treatment with anti EGFR (epidermal growth facor receptor), every 4 cures. At the end of treatment or after more than 36 treatment cures, a final sample will be taken.

No results of the samples will be communicated to the investigator, the sponsor will centralize these results for the final analysis of the study.

Inclusion Criteria:

• Patient with histologically confirmed metastatic colorectal cancer
• Patient treated in the first line by one of the treatments below and according to a bi-monthly schema for cetuximab: FOLFIRI (elvorin + 5 Fluorouracil + irinotecan) ou FOLFOX (elvorin + 5 Fluorouracil + oxalplatin) + Cetuximab* (Erbitux) ; FOLFIRI ou FOLFOX + Panitumumab (Vectibix); FOLFIRINOX ou FOLFOXIRI ((elvorin + 5 Fluorouracil + oxaliplatin + irinotecan) + Cetuximab* (Erbitux); FOLFIRINOX ou FOLFOXIRI + Panitumumab (Vectibix) For patient treated cetuximab administration will be bi-monthly
• Patient with at least one evaluable metastatic target according to RECIST 1.1 (Response Evaluation Criteria in Solid Tumors)
• Wild RAS (rat sarcoma viral oncogene homolog) status detected by standard tissue test, on primary tumor and / or metastasis
• Wild BRAF (murine sarcoma viral oncogene homolog B) status detected by standard tissue test, on primary tumor and / or metastasis
• Man or woman> 18 years old
• Signed informed consent before any specific procedure to study
• Patient affiliated to the social security or equivalent

Exclusion Criteria:

• Previous treatment with an anti-EGFR (epidermal growth factor receptor)
• Patient with a multifocal primary tumor
• RAS (rat sarcoma viral oncogene homolog) status mutated or not detectable on tissue analysis
• BRAF (murine sarcoma viral oncogene homolog B) status mutated or undetectable on tissue analysis
• Patient receiving adjuvant chemotherapy or radiotherapy within <14 days
• History of other cancer in the last 5 years (except in-situ carcinoma of the cervix and cutaneous carcinoma excluding melanoma treated optimally)
• Blood transfusion (whole blood, red blood cell, platelets...) in the previous week
• Patients with psychological, familial, sociological or geographic conditions potentially not favorable to the good observance of the study protocol and the follow-up
• Legal incapacity or limited legal capacity

Participation in another interventional clinical trial - biomedical research (therapeutic strategy type) is not excluded provided that it is use an Anti-EGFR with a AMM (marketing authorization), (Cetuximab - Panitumumab) with a dose and a standard administration rhythm (according to the AMM).