How Does Cetuximab Work? — The Anti-EGFR Antibody Explained

No. Cetuximab is a monoclonal antibody, not a chemotherapy drug. It works by targeting a specific protein on cancer cells rather than by damaging all rapidly dividing cells the way chemotherapy does. Its side effects are different — a characteristic skin rash and low magnesium levels are most common, while chemotherapy-associated hair loss and mouth sores are not typical of cetuximab alone. When it is given alongside chemotherapy, you may experience side effects from both.

EGFR sits at the top of a growth pathway inside the cancer cell, and RAS controls a step further down the same pathway. If RAS is mutated, it keeps sending the grow signal even when EGFR is blocked by cetuximab. NCCN and ESMO guidelines require RAS testing before treatment, not as a formality but because a mutation means the drug is unlikely to help. The test is done on your tumour tissue, usually from your existing biopsy, so it does not typically require a new procedure.

This depends on what it is being used for and how your tumour responds. In some head and neck cancer settings it runs alongside a course of radiotherapy and then stops. In colorectal cancer it may continue as long as the disease is responding and the side effects are manageable. Your oncologist will review response regularly, usually with imaging, and will discuss the ongoing plan with you at each stage. There is no single fixed duration.

Yes. In most patients the rash improves once treatment is stopped or paused. During treatment it can be managed with moisturisers, sun protection, and in some cases a prescription antibiotic cream. Tell your team if the rash is affecting your sleep or daily life — it can often be managed without reducing the dose. Do not stop using any prescription skin treatment without checking first, because untreated rash can become infected.

For most patients, yes. There is no specific food restriction. Because cetuximab can lower magnesium levels, your team may advise eating magnesium-rich foods or taking supplements alongside your regular blood monitoring. If you are also receiving chemotherapy, those drugs may carry their own dietary guidance. Tell your team about any supplements, herbal preparations or traditional remedies you are taking — some can interact with treatment in ways that are not always obvious, and your team cannot help you if they do not know.

Cetuximab is administered as a day-care infusion at CION centres. Your oncologist will confirm whether it is appropriate for your specific diagnosis and will arrange RAS testing beforehand if it has not already been done. Response-assessment scans during treatment are coordinated with partner imaging centres.