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Selective Internal Radiotherapy Treatment (SIRT) is a type of cancer treatment that uses tiny radioactive beads called SIR-Spheres® (Sirtex Medical Ltd). SIRT is a way of treating liver tumours| with internal radiotherapy|.
SIRT is used to treat liver tumours that can’t be removed by surgery. It’s most commonly used to treat secondary tumours (metastases) in the liver from a cancer that started in the large bowel (primary bowel cancer|). It may occasionally be used to treat liver secondaries from other types of cancer. SIRT can also be used to treat primary liver cancer|.
This information describes how SIRT works, how it’s given and some of the possible side effects. We hope that it answers your questions. If you have any further questions you can ask your doctor or nurse at the hospital where you are having your treatment.
The National Institute for Health and Clinical Excellence (NICE|) currently gives advice about which new treatments should be available on the NHS. NICE has reviewed the use of SIRT. It found SIRT to be a safe treatment, but recommends that further monitoring and research is needed to see if it improves survival and quality of life. SIRT isn’t widely available so if it’s suitable for you, you may have to travel to another hospital to have the treatment. You may be given SIRT as part of a research trial.
Radiotherapy treatment is the use of high-energy x-rays and similar rays (such as electrons) to treat disease. It works by damaging DNA (our genetic material) in the cancer cells.
Radiotherapy can be given from outside the body using x-rays or from within the body as internal radiotherapy|, called brachytherapy. External radiotherapy is given using equipment similar to a large x-ray machine. This type of radiotherapy can only be given in low doses to the liver as radiotherapy can cause too much damage to normal liver cells.
SIRT is a way of delivering high-dose internal radiotherapy to liver tumours. It uses tiny coated beads called microspheres, which contain a radioactive substance called Yttrium. Cancer cells need a blood supply to receive oxygen and nutrients. SIRT beads lodge in the blood vessels that supply tumours.
They then destroy the blood vessels and stop the flow of blood to tumours - this is called radioembolisation.
The radiation given off by the beads extends to an area of about 4mm around them. This means that there is little damage to healthy tissue in the liver and no significant level of radiation outside the body. The radioactivity of the beads decreases quickly, and its treatment effect occurs mainly within the first two days. The beads remain in the body but don’t cause any problems.
The beads are injected into a thin, flexible tube called a catheter, which is inserted into the blood vessel that supplies the liver (hepatic artery). As tumours in the liver get their blood supply from this blood vessel, SIRT directly targets cancer cells.
Pathway of the SIRT catheter
View a large version of the diagram of the pathway of a SIRT catheter|
Your doctor will arrange some of the following tests to decide if SIRT is suitable for you.
These can include a full blood count, which measures the number of different blood cells in your body and a test to check how well your kidneys and liver are working. If you have a bowel cancer|, you may have a carcinoembryonic antigen (CEA) test, which is a protein that's produced by bowel cancer cells and is called a tumour marker.
You will usually have a CT (computerised tomography), MRI (magnetic resonance imaging) or PET (positron emission tomography) scan. These scans are used to show how much of the liver is affected by the tumour.
An angiogram is a procedure where x-rays are used to examine blood vessels. It usually takes place in the radiology (x-ray) department of the hospital. The angiogram shows the blood supply to your liver and allows your doctor to plan the correct dose of SIRT for you.
You'll be asked not to eat or drink anything for several hours before your angiogram. If you take any medication, you'll be instructed to take it as normal. If you take drugs that can thin your blood, such as aspirin or warfarin, you'll be told when to stop taking these.
You will be given a local anaesthetic injection to numb the skin. The doctor then makes a small cut and inserts a catheter into a blood vessel in your groin (femoral artery). The catheter is then guided to the liver. Dye is injected into the catheter and x-rays are taken. This shows where the beads would travel to in the body through the bloodstream. Your doctor can then close off any blood vessels that would take SIRT beads from the liver to other parts of the body.
After the procedure, you'll need to lie flat for a few hours to allow the site where the catheter went into your groin to heal properly. Try to drink at least 1.5 litres (3 pints) of water in the 24 hours after your planning angiogram, to help clear the dye from your body. You shouldn’t drive for 24 hours after the procedure and will need to avoid heavy lifting and vigorous exercise for three days.
Your treatment will take place a week or two after your planning angiogram. You may need to stay in hospital overnight or for a few days to have your treatment.
Another angiogram is carried out and this time SIRT beads are injected into the catheter. This usually takes less than an hour. You will be conscious during the procedure, but will be given medication to help you relax, which may make you feel drowsy. You'll also be given anti-sickness medicine. If you have any pain during SIRT, let your doctor know so they can give you painkillers.
Your doctor or nurse will tell you if there are any specific precautions you need to take while the radioactivity of the SIRT beads decreases. They will explain this before you have your treatment. They will also tell you about any possible side effects you may have.
Each person’s reaction to SIRT is different. Some people have very few side effects, while others may experience more. The side effects described here won't affect everyone who has SIRT. Side effects are usually temporary and will go away in time.
We have outlined the most common side effects but haven't included those that are rare and therefore unlikely to affect you. If you notice any effects which aren't listed here, discuss them with your doctor or nurse.
There may be bruising or a small lump at the site where the catheter went into your groin. If you notice any bleeding, redness, swelling, discharge or pain, let your nurse or doctor know straight away.
Nausea| can last for a few days. You'll be given an anti-sickness drug before treatment. Tablets (anti-emetics) can be prescribed if nausea continues.
Some people experience pain in the tummy (abdomen) during SIRT. Painkillers can be given to help with this. Let your doctor know about any pain you experience during treatment.
Rarely, some beads may escape from the liver and cause painful inflammation of the lining of the stomach or bowel. This is called gastritis and you may be prescribed medicine to take regularly to help with it. Let your doctor or nurse know about any pain you experience straight away.
You may have a fever due to your treatment. This should stop after a few days. Fever is a common side effect of SIRT but can also be a sign of infection. If your temperature goes above 38°C (100.4°F), contact your doctor or the hospital straight away.
Tiredness| can last from a few days up to several weeks after treatment. Getting adequate rest and a balanced diet is important in order to help your body recover. Keeping a treatment diary can help you record your energy levels and plan activities for when you're feeling stronger.
SIRT has some effect on normal liver cells and this may cause changes to your liver function test. Your doctor will monitor this by taking regular blood samples. The changes usually resolve after a few weeks.
Rarely SIRT can cause more severe side effects. This can happen when normal liver cells get too much radiotherapy or when beads travel to other parts of the body. This may cause damage to organs in the body including the liver, bowel, pancreas, stomach and lungs. This is why you're carefully assessed before treatment, and why SIRT is only administered by specialist multidisciplinary teams. It’s important that you discuss any concerns regarding your treatment or its possible side effects with your doctor or nurse.
Your doctor will arrange for you to have further tests to see how well your treatment has worked. This may include further blood tests and scans. Some people need to have a second treatment. Your doctor will let you know if this is necessary.
SIRT can be given in combination with chemotherapy|. Giving the treatments together may be more effective but may also increase some of the side effects, including lowered resistance to infection (neutropenia)|. Your doctor will let you know if SIRT and chemotherapy are suitable for you and how any side effects will be managed.
A clinical trial called FOXFIRE is looking at the benefits of adding SIRT to chemotherapy for people with liver secondaries from cancer of the large bowel. Your doctor will advise you if this trial is suitable for you.
It’s not advisable to become pregnant before having SIRT as the developing baby may be harmed. It’s important to use effective contraception before treatment and for at least two months afterwards. Women having SIRT should not breastfeed after treatment until they're told it is safe to do so. Discuss these issues with your doctor or nurse before having SIRT.
We have more information about fertility| and cancer treatment.
This information has been compiled using information from a number of reliable sources including:
With thanks to: Dr Greg Wilson, Consultant Medical Oncologist; and the people affected by cancer who reviewed this edition. Reviewing information is just one of the ways you could help when you join our Cancer Voices| network.
For answers, support or just a chat, call the Macmillan Support Line free (Monday to Friday, 9am-8pm)
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