Panitumumab (Vectibix)

Panitumumab is pronounced pan-ee-chew-moo-mab. It is also known by its brand name Vectibix. It is a type of monoclonal antibody. Monoclonal antibodies are a type of biological therapy.

Panitumumab is a treatment for advanced bowel cancer when other treatments are no longer working. Advanced cancers have spread from where they started to another part of the body.

You may also have panitumumab as part of a trial for other cancers including

• Advanced stomach cancer
• Advanced cancer of the oesophagus (food pipe)

Panitumumab only works on cancers that have a normal Kras gene. This gene helps to control how cells grow and divide. You will need to have tests to check if this gene is normal.

Some cancer cells have proteins called epidermal growth factor receptors (EGFR) on their surface. Epidermal growth factor (EGF) is another type of protein made naturally in the body that attaches to this receptor. This triggers the cell to grow and divide into more cells. Panitumumab works by attaching itself to the EGF receptors to block EGF protein from reaching the cancer cells. It also helps the immune system to recognise the cancer cells so that it can destroy them.

Panitumumab works better if your cancer cells have a lot of epidermal growth factor receptors. Before you have panitumumab, you may have tests to check the amount of epidermal growth factor receptors.

You have panitumumab through a drip into a vein (infusion) through a pump. You have the first treatment over 60 to 90 minutes every 2 weeks. You usually have it for a few months or as long as it is working.

The side effects associated with panitumumab are listed below. The side effects may be different if you are having it with other drugs.

More than 10 in every 100 people have one or more of these.

• A skin reaction occurs in 9 out of 10 people (90%) – you may have a rash similar to acne on your face, neck and trunk or your skin may be dry and itchy. This can be severe for some people. The reaction usually starts about 10 days after the start of treatment and gets better within a month of finishing treatment. You may need to have a lower dose of the drug or stop treatment for a short time.
• Sensitivity to sunlight – wear sun cream and cover up when you are having treatment, as sunlight can make skin reactions worse
• Nail infection
• Diarrhoea affects 3 out of 10 people (30%) – drink plenty of fluid and tell your doctor or nurse if it becomes severe or continues for more than 3 days
• Tiredness affects 1 in 2 people (50%) during and after treatment – most people find their energy levels are back to normal within 6 months to a year
• Feeling or being sick happens in about 1 out of every 5 people (20%) but is usually well controlled with anti sickness drugs
• Sore, watery, eyes (conjunctivitis) or dry, itchy eyes occur in around 1 in 5 people (20%), very rarely this can be inflammation of the cornea and you may need to stop treatment. Tell your doctor if you have any eye symptoms.
• Your eyelashes may grow in a different direction to normal

Between 1 and 10 in every 100 people have one or more of these.

• Headaches
• Dehydration in people who have severe diarrhoea – drink plenty of fluids
• Low levels of magnesium, potassium and calcium in your blood – you will have regular blood tests to check the levels of these minerals
• A cough and shortness of breath
• A sore mouth – some people develop mouth ulcers
• An allergic reaction while you have the treatment, causing a high temperature, chills, shivering (rigors), a headache, and feeling sick. A few people have a more severe reaction, with wheezing, an itchy rash, and a drop in blood pressure. Your nurse will give you medicines before treatment to try to prevent a reaction. They will stop or slow your drip if it occurs. Let your doctor or nurse know if you have fever or chills the night after the drip. 
• Women may stop having periods (amenorrhoea) but this may be temporary
• Loss of fertility – we don’t know exactly how this drug affects fertility so do talk with your doctor before starting treatment if having a baby is important to you
• Panitumumab may have a harmful effect on a baby developing in the womb – do talk to your doctor about contraception before having treatment if there is any chance that you or your partner could become pregnant

Fewer than 1 in 100 people have these.

• Increased risk of blood clots in the lungs (pulmonary embolism)
• A build up of fibrous tissue in the lungs (pulmonary fibrosis) – let your doctor know if you have a cough or breathlessness that starts some time after your treatment has ended

You won’t get all the side effects mentioned here and some may be very mild. A side effect may get worse through your course of treatment. Or you may have more side effects as the course goes on. This depends on

• How many times you've had a drug before
• Your general health
• How much of the drug you have (the dose)
• Other drugs you are having

Talk to your doctor, pharmacist or nurse about all your side effects so they can help you manage them. Your nurse will give you a contact number. You can ring them if you have any questions or problems. They can give you advice or reassure you. If in doubt, call them.

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and other over the counter remedies – some drugs can react together.