This is a national, multicentric, prospective, observational trial. The decision to prescribe FOLFOX or FOLFIRI plus panitumumab or FOLFOX or FOLFIRI plus cetuximab must have been freely taken by the clinician prior to the study entry for each patient included. Each physician will see his/her patients within the context of routine visits, without any special visit being organised for the purposes of the study. Therefore, the doctor-patient relationship and patient follow-up are not modified. Physicians are totally free to decide on their patients' therapeutic management.

EORTC QLQ-C30 and DLQI questionnaires will be completed by the patients at baseline (Day 1 of Cycle 1), at the first day of every other cycle (every 2 weeks) thereafter, and at ""End of Study Visit" (within 28 days from the end of treatment with anti-EGFR or withdrawal from study for any reason).

Before every cycle, adverse events will be recorded and graded according to NCI CTCAE v4.0. Treatment's modifications in terms of cycles' delay, dose reductions or drugs' interruptions will be recorded.

Concomitant approaches to prevent or treat dermatological toxicities during the treatment will be registered.

Inclusion Criteria:- Adult (>= 18 years old) RAS wild-type metastatic colorectal cancer patients candidate to receive FOLFOX or FOLFIRI plus panitumumab or FOLFOX or FOLFIRI plus cetuximab as upfront treatment as per clinical practice

• Willingness and ability to comply with the protocol
• Written informed consent to study procedures
• Exclusion Criteria: - Patients receiving a treatment under clinical investigation may not be included in the study
• Previous treatment with an anti-EGFR monoclonal antibody

Adult (>= 18 years old) RAS wild-type metastatic colorectal cancer patients candidate to receive FOLFOX or FOLFIRI plus panitumumab or FOLFOX or FOLFIRI plus cetuximab as upfront treatment as per clinical practice. Willingness and ability to comply with the protocol. Written informed consent to study procedures.

De-identified individual patient data for variables necessary to address the specific research question in an approved data sharing request

Data sharing requests relating to this study will be considered beginning 18 months after the study has ended and either 1) the product and indication (or other new use) have been granted marketing authorization in both the US and Europe or 2) clinical development for the product and/or indication discontinues and the data will not be submitted to regulatory authorities. There is no end date for eligibility to submit a data sharing request for this study

Qualified researchers may submit a request containing the research objectives, the Amgen product(s) and Amgen study/studies in scope, endpoints/outcomes of interest, statistical analysis plan, data requirements, publication plan, and qualifications of the researcher(s). In general, Amgen does not grant external requests for individual patient data for the purpose of re-evaluating safety and efficacy issues already addressed in the product labelling. Requests are reviewed by a committee of internal advisors, and if not approved, may be further arbitrated by a Data Sharing Independent Review Panel. Upon approval, information necessary to address the research question will be provided under the terms of a data sharing agreement. This may include anonymized individual patient data and/or available supporting documents, containing fragments of analysis code where provided in analysis specifications. Further details are available at the link below.