Cetuximab is a monoclonal antibody that inhibits the epidermal growth factor receptor (EGFR) which is present on the surface of some cancer cells. Cetuximab binds to the receptor, preventing epidermal growth factor (EGF) from binding to it and stimulating growth of the cancer cells. Cetuximab is used to treat squamous cell cancer of the head and neck. Cetuximab is commonly used alongside chemotherapy as a first line approach to cancer that has spread or is recurring. It is also used alongside radiation therapy in localized disease. Patients with metastatic colorectal cancer that expresses EGFR may be treated with cetuximab in combination with chemotherapy or cetuximab may be given as a single therapy to patients who have failed to respond to irinotecan- and oxaliplatin-based regimens.