Inclusion Criteria:

- Age above 18 years.

- Histology or cytology proven KRAS-WT mCRC.

- Performance status ≤3 (Eastern Cooperative Oncology Group [ECOG] classification)

- Life expectancy of more than 12 weeks.

- Written informed consent.

- In women of childbearing potential, appropriate contraceptive measures must be used
during treatment with cetuximab and for 6 months following the last dose of
cetuximab.

Exclusion Criteria:

- Past systemic immune therapy for disease other than cancer.

- Past immune or other target therapy for cancer (not including bevacizumab).

- Presence of acne or acneiform rash prior to starting treatment with cetuximab.

- Patients with treatment plan of cetuximab and capecitabine combination.

- For female patients: the patient is pregnant or lactating.