The study will be conducted in patients with metastatic colorectal cancer (mCRC) harboring a BRAFV600E mutation, to collect clinical data and biological samples to be used for research but also to gather real-world clinical data concerning the treatments and the survival outcomes in patients with this pathology.

Despite substantial progress made in the first- and second line mCRC settings, there are still unmet clinical needs for patients harboring BRAFV600E mutations, especially those with microsatellite stability (MSS) / proficient mismatch repair (pMMR) tumor. The overall survival and access to different treatment in the real-life setting are unknown. Moreover, patient prognosis remains poor and therapeutic resistance to combinations with BRAF inhibitors, is at present, nearly universal. Therefore, it seems essential to prospectively collect clinical and biological data about this rare mCRC subtype. These data will allow us to improve knowledge and to identify clinical and biological factors that could drive therapeutic decisions, predict resistance to treatments, and that are prognostic for survival. In this context, we designed this large, prospective, cohort study to collect clinical data and biological samples to be used for research but also to gather real-world clinical data concerning the treatments and the survival outcomes in patients with BRAFV600E mCRC.

This collection of clinical and biological data (tumor tissue and blood samples) will allow us to identify predictive and prognostic biomarkers with several research work packages planned:

i. To evaluate the circulating tumor DNA (ctDNA) during the metastatic first-, second-, and third-line treatment to:

• Evaluate its positive and negative predictive value.
• Identify molecular alterations preceding and explaining clinical resistance during BRAF/EGFR inhibition therapy and immunotherapy.

ii. To evaluate BRAFV600E mCRC immune environment both at the tumor and blood level (immunomonitoring).

iii. To study specific the dMMR/MSI BRAFV600E subgroup. Furthermore, the data collected will describe the therapeutic management of BRAFV600E mCRC patients in the routine-practice setting which will bring very useful data. The results of the COBRAF study could lay the groundwork to better understand BRAFV600E mCRC and to identify prognostic and predictive biomarkers helping the development of new therapeutic approaches in this population.

Inclusion Criteria:

1. Men and women aged 18 years or older
2. Histologically confirmed BRAFV600E metastatic colorectal cancer (mCRC), chemotherapy-naive in the metastatic setting or having initiated a first line of chemotherapy in the metastatic setting (except encorafenib-cetuximab treatment)
3. Available tumor tissue sample obtained before inclusion with sufficient tissue left for biological studies. Patients with only fine-needle aspirations are not eligible.
4. Known MMR/microsatellite status (immunohistochemistry [IHC] and polymerase chain reaction [PCR]) (or under analysis)
5. Patients must have signed a written informed consent form prior to any trial specific procedures. If the patients are physically unable to give their written consent, a trusted person of their choice, not related to the investigator or the sponsor, can confirm in writing the patient's consent.
6. Patients must be willing and able to comply with the study procedures
7. The patient must be affiliated to a social security system or benefit of such a system.

Exclusion Criteria:

1. Patient with another cancer concomitantly with the mCRC requiring treatment or influencing the prognosis according to the medical staff.
2. Patients for whom the follow-up will not be assured by the investigator or its team.
3. Any condition that may jeopardize patient participation in the study as well as non-contraception for men and women with child-bearing potential, and pregnancy or breast feeding for women.
4. Persons deprived of their liberty or under protective custody or guardianship.

Unicancer will share de-identified individual data that underlie the results reported. A decision concerning the sharing of other study documents, including protocol and statistical analysis plan will be examined upon request.

Unicancer will consider access to study data upon written detailed request sent to Unicancer, from 6 months until 5 years after publication of summary data.

The data shared will be limit to that required for independent mandated verification of the published results, the applicant will need authorization from Unicancer for personal access, and data will only be transferred after signing of a data access agreement.