How cetuximab works

Cetuximab is a type of drug called a monoclonal antibody. These drugs are sometimes called targeted therapies. They work by ‘targeting’ specific proteins (receptors) on the surface of cells.

Certain cancer cells have receptors on their surface called epidermal growth factor receptors (EGFRs). Activating them triggers the cancer cells to divide and grow. Cetuximab locks on to the EGFRs and stops the cancer cells growing. It may also make the cancer cells more sensitive to chemotherapy and radiotherapy.

When it is used to treat bowel cancer, cetuximab only works on bowel cancers that have a normal RAS gene. The RAS gene helps control cell growth. Doctors will test the cancer cells before treatment to see if there are changes (mutations) in this gene.

It is best to read this information with our general information about the type of cancer you have. During treatment, you will see a cancer doctor and a cancer nurse. This is who we mean when we mention doctor or nurse in this information.

When cetuximab is used

Cetuximab can be used to treat bowel cancer that has spread (advanced cancer). You usually have it along with chemotherapy.

Cetuximab can also be used to treat some cancers of the head and neck that have started to spread into surrounding tissue (locally advanced) or those that have spread to other parts of the body (advanced). It is usually given with radiotherapy, but it can also be given with chemotherapy.

Cetuximab may only be available in some situations. Your cancer doctor can tell you if it is appropriate for you. Some people may be given it as part of a clinical trial.

If a drug is not available on the NHS, there may be different ways you can still have it. Your cancer doctor can give you advice. We have more information about what to do if a treatment isn’t available.

How cetuximab is given

A nurse gives you cetuximab into a vein as a drip (intravenous infusion). Or you may have it through a small infusion pump. You have the first treatment slowly, over about 2 hours. If you don’t have any problems, you can have your next treatment over an hour.

Afterwards you stay in the clinic for about an hour, so the nurses can be sure you don’t have a reaction to the drug. If you are having chemotherapy on the same day, you usually have it an hour after cetuximab. You usually have cetuximab once a week, or every 2 weeks.

Possible side effects

We explain the most common side effects of this treatment here. We also include some less common side effects. You may get some of the side effects we mention here, but you will not get them all. Always tell your doctor or nurse about any side effects you have.

If you have other cancer drugs along with this treatment, some side effects may be worse. You may also have side effects not listed here. We have more information about chemotherapy and radiotherapy.

If a side effect is more severe, your doctors may need to reduce the dose, or stop the treatment for a short time. Some people may have this treatment stopped completely.

Your doctor can give you drugs to help control some side effects. It is very important to take them exactly as your nurse or pharmacist has explained. This will help the drugs work as well as possible for you. Your nurse will give you advice about managing side effects. Most side effects start to improve after treatment has finished.

Serious and life-threatening side effects

Some cancer treatments can cause severe side effects. Rarely, these may be life-threatening. Your cancer doctor or nurse can explain the risk of these side effects to you.

Contact the hospital

Your nurse will give you telephone numbers for the hospital. If you feel unwell or need advice, you can call them at any time of the day or night. Save these numbers in your phone or keep them somewhere safe.

More information

We cannot list every side effect for this treatment. There are some rare side effects that are not listed. You can visit the electronic Medicines Compendium (eMC) for more detailed information.

Side effects during treatment

Some people have an allergic reaction to cetuximab. This can happen when it is given or for up to an hour afterwards. You will be given drugs before the infusion to reduce the chance of a reaction happening. A reaction is usually mild but, rarely, can be more severe. If you have a reaction, the nurses can usually treat this by slowing or stopping the drip. You will have the rest of your treatments at a slower rate.

You will be checked closely during treatment. But always tell your nurse or doctor if you feel unwell or have any of the following symptoms:

  • flu-like symptoms, such as a headache, feeling flushed, having a fever, chills or dizziness
  • red, warm and itchy bumps on the skin (like nettle rash)
  • a feeling of swelling in the lips, tongue or throat
  • breathlessness, wheezing, a cough or suddenly finding it hard to breathe
  • a tight chest or chest pain.

Rarely, people may get a reaction a few hours after treatment. If you have any of the symptoms above or feel unwell after you get home, contact the hospital straight away for advice.

You are more likely to have a serious allergic reaction to cetuximab if you have:

  • an allergy to red meat
  • an allergy to tick bites (a tiny spider-like insect found in woodland and heath areas).

You must tell your cancer doctor and nurse if you have either of these allergies before they give you cetuximab.

Common side effects

Skin changes

You may get an acne-like rash on the face, neck and body during the first three weeks of treatment. Your doctor can prescribe treatment to reduce the rash. The skin may also become dry, itchy and flaky. These side effects usually improve when treatment finishes. Our information about skin changes during treatment may be helpful.

Very rarely, people may have a very severe skin reaction. The symptoms can include large blisters, peeling skin and sores in your mouth. You may also have a fever (high temperature). You must contact the hospital straight away if this happens, as it may cause very serious problems.

Always tell your doctor or nurse about any skin changes. They can give you advice and prescribe creams for your skin or medicines to help. If you have severe skin problems, they may lengthen the time in between your treatments or lower the dose.

Feeling tired

Feeling tired is a common side effect. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can give you more energy. If you feel sleepy, do not drive or operate machinery.

Feeling sick

Your doctor can give you anti-sickness drugs to help prevent or control sickness. If you still feel sick, tell your doctor. They can prescribe other anti-sickness drugs that may work better for you.


You may have frequent or loose bowel movements. This can usually be easily controlled with medicines, but tell your doctor if it is severe or continues. If you have diarrhoea, it is important to drink plenty of fluids to stop you getting too dehydrated. But avoid alcohol and coffee.

Sore mouth and nose

The lining of your mouth and nose may become sore. You may have mouth ulcers or nosebleeds. Tell your nurse or doctor if you have any of these changes. They can give you medicines to help. Clean your teeth or dentures morning and night and after meals. Use a soft-bristled or children’s toothbrush. Your nurse can give you advice on looking after your mouth.

Hair changes

Your eyelashes may grow longer and curlier. You may notice that your head and body hair is finer, curlier or more brittle. Men may notice less beard growth. Some people may lose their hair. This may happen slowly over several months. These changes usually improve when treatment is over. We have more information about coping with hair loss.

Nail changes

You may notice changes to your nails. They may become brittle and break easily. Wear gloves when washing dishes or using detergents to help protect your hands and nails. If the area around your nails becomes inflamed, tell your doctor straight away.


This treatment may cause headaches. If this happens, tell your doctor or nurse. They can give you painkillers.

Sore eyes

Cetuximab may make your eyes feel dry, sore, red and itchy. Tell your doctor so they can prescribe eye drops to help with this. If this doesn’t improve or you have changes to your vision or pain in the eye, tell your doctor. Less commonly, cetuximab may cause inflammation of the eyelid. It is important to contact your doctor straight away if this happens.

Liver changes

This treatment may cause changes in the way your liver works. This will return to normal when the treatment finishes. Your doctor or nurse will take regular blood samples to check your liver is working properly.

Reduced levels of magnesium in the blood

Magnesium helps keep nerves and muscles working properly. You will have regular blood tests to check your levels of magnesium. Your doctor may prescribe you magnesium supplements if the levels are too low.

Less common side effects

Blood clots

This treatment can increase the chances of a blood clot. A clot can cause:

  • pain, redness and swelling in a leg or arm
  • breathlessness
  • chest pain.

Contact your doctor straight away if you have any of these symptoms. A blood clot is serious, but your doctor can treat it with drugs that thin the blood. Your doctor or nurse can give you more information.


Let your doctor know if you become breathless or are more breathless than usual. Rarely, cetuximab can cause a condition in which the lungs become inflamed. This can be very serious. Contact the hospital straight away if you suddenly become breathless or your breathing gets worse.

Other information

Other drugs

Some medicines, including ones you buy in a shop or chemist, can be harmful while you are having this treatment. Tell your cancer doctor about any drugs you are taking, including vitamins, herbal drugs and complementary therapies.


Your doctor will advise you not to get pregnant or make someone pregnant while having this treatment and for some time afterwards. The drugs may harm the developing baby. It is important to use effective contraception.


Women are advised not to breastfeed while having this treatment. This is because the drugs could be passed to the baby through breast milk.


Doctors don’t yet know how this treatment may affect your fertility (the ability to become pregnant or father a child). If you are worried about this, talk to you doctor before treatment starts.

Medical and dental treatment

If you need medical treatment for any reason other than cancer, always tell the doctors and nurses that you are having cancer treatment. Give them the contact details for your cancer doctor so they can ask for advice.

If you think you need dental treatment, talk to your cancer doctor or nurse. Always tell your dentist you are having this treatment.

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