Selective internal radiation therapy (SIRT)

Selective internal radiation therapy (SIRT) uses tiny radioactive beads to treat liver tumours that can’t be removed by surgery. SIRT is most commonly used to treat secondary tumours (metastases) in the liver from a cancer that started in the large bowel. SIRT isn’t yet widely available in the UK. Your doctor will arrange for tests to decide whether SIRT is suitable for you. These may include a blood test, a scan or an angiogram (x-ray of blood vessels).

Tumours in the liver get their blood supply from a blood vessel called the hepatic artery. For treatment with SIRT a thin tube called a catheter is inserted into this blood vessel. Radioactive beads are injected into the catheter and make their way into the smaller blood vessels that supply the tumour. The beads deliver radiation directly to the cancer cells. They cause little damage to healthy liver tissue.

Most people have very few side effects, but some may experience more. They may include:

  • problems at the catheter injection site
  • feeling sick (nausea)
  • tummy (abdominal) pain
  • fever
  • tiredness
  • changes to the liver.

Advice and treatment is available to help with any side effects.

What is selective internal radiation therapy (SIRT)?

Selective internal radiation therapy is a type of cancer treatment that uses tiny radioactive beads. It is a way of treating liver tumours (both primary and secondary) with internal radiotherapy.

SIRT is used to treat liver tumours that can’t be removed by surgery. SIRT is 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 metastases from other types of cancer. SIRT can also be used to treat primary liver cancer.

The National Institute for Health and Care Excellence (NICE) gives advice about which treatments should be available on the NHS. NICE currently recommends that SIRT can be used for people with secondary liver tumours who have previously been treated with chemotherapy. However, it recommends that further monitoring and research is needed to see whether SIRT improves survival and quality of life. People who have not already had chemotherapy treatment should first be offered a research trial, such as FOXFIRE. This trial is looking at whether giving chemotherapy and SIRT together is more effective than chemotherapy on its own. Your doctor or specialist nurse can give you more information.

NICE also recommends that SIRT is safe to be used to treat primary liver cancer, but that more research is needed to see how effective it is. NICE doesn’t recommend SIRT to treat primary bile duct cancer (cholangiocarcinoma) without monitoring or as part of a research trial.

In England and Scotland, SIRT is now available through a special funding programme called Commissioning through Evaluation. The programme aims to increase the number of people who can have specialist radiotherapy treatments. Your doctor can give you more information. If you live in Wales or Northern Ireland, you can find out from your cancer specialist whether SIRT is available.

SIRT isn’t widely available, so if it’s suitable for you, you may have to travel to another hospital to have it. You may be given SIRT as part of a research trial.

How SIRT works

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 (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, because radiotherapy can cause too much damage to normal liver cells.

Cancerous tumours in the liver usually have a different blood supply to the normal liver. SIRT is a way of delivering high-dose internal radiotherapy to liver tumours by giving treatment through the blood system supplying the tumours. There are two products currently available for this treatment. Both use tiny 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 the tumours, and the SIRT beads give off radiation. This destroys the blood vessels and stops the flow of blood to the tumours. This is called radio-embolisation.

The radiation given off by the beads extends to an area of about 4mm around them. This means 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. Its treatment effect mostly happens in the first two days. The beads stay in the body but don’t cause any problems.

Tests before your SIRT treatment

Your doctor will arrange some of the following tests to decide whether SIRT is suitable for you.

Blood tests

This can include a full blood count, which measures the number of different blood cells in your body. It can also include a test to check how well your kidneys and liver are working. If you have bowel cancer, you may have a carcinoembryonic antigen (CEA) test. CEA is a protein that's produced by bowel cancer cells and is called a tumour marker.

Other tests

You will usually have a CT (computerised tomography) scan, an MRI (magnetic resonance imaging) scan or a PET (positron emission tomography) scan. These scans are used to show how much of the liver is affected by the tumour.

Planning angiogram

An angiogram is where x-rays are used to look at blood vessels. It usually happens in the radiology (x-ray) department of the hospital. A planning angiogram shows the blood supply to your liver and lets your doctor see where the SIRT beads would go when they are injected into your liver.

You will be asked not to eat or drink anything for several hours before your angiogram. If you take any medication, you will be told to take it as normal. If you take drugs that can thin your blood, such as aspirin or warfarin, you will be told when to stop taking them.

You will be given a local anaesthetic injection to numb the skin. The doctor then makes a small cut. They insert a thin, flexible tube called a catheter into a blood vessel in your groin (femoral artery). Then they guide the catheter to the liver. They inject dye into the catheter and take x-rays. This shows where the SIRT beads would travel to in the body through the bloodstream. The doctor can then close off any blood vessels that would take SIRT beads away from the liver to other parts of the body.

During the angiogram, you will be injected with a radioactive ‘tracer’ that is similar to the SIRT beads. After the angiogram you will have a gamma camera scan, which can detect this tracer and show where the SIRT beads will go to in your body. This helps your doctor know it is safe for you to have the treatment.

After the angiogram, you will need to lie flat for a few hours to let the site where the catheter went into your groin heal properly. Try to drink at least 1.5 litres (3 pints) of water in the 24 hours after your planning angiogram. This will help clear the dye from your body. You shouldn’t drive for 24 hours after the procedure. And avoid heavy lifting and vigorous exercise for three days.

How SIRT is given

A thin, flexible tube called a catheter is inserted into the blood vessel that supplies the liver (hepatic artery). The beads are injected into the catheter. Because tumours in the liver get their blood supply from the hepatic artery, SIRT directly targets cancer cells.

Sirspheres - colour
Sirspheres - colour

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Having SIRT

Your treatment will happen 1–2 weeks after your planning angiogram. You may need to stay in hospital overnight or for a few days to have your treatment.

Another angiogram is done, 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. This may make you feel drowsy. You will also be given anti-sickness medicine. If you have any pain during SIRT, let your doctor know so they can give you painkillers.

Before you have your treatment, 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 also tell you about any side effects you may have.

When you go home, you may have medication to take after the treatment. Your doctor or nurse will explain this to you. Some medications are provided to help reduce the chance of serious side effects, so it is important to let your team know if you cannot take them.

Side effects of SIRT

Each person’s reaction to SIRT is different. Most people have very few side effects, but some may experience more. The side effects described here will not affect everyone who has SIRT. Side effects are usually temporary and will go away in time. 

We have listed the most common side effects, but we haven't included side effects that are rare and therefore unlikely to affect you. If you notice any side effects that aren't listed here, discuss them with your doctor or nurse. 

Problems at your injection site

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. 

Feeling sick (nausea) 

Nausea can last for a few days. You'll be given an anti-sickness drug before treatment. If nausea continues, you can be prescribed tablets (anti-emetics). 

Tummy (abdominal) pain 

Some people have tummy pain during SIRT. Painkillers can be given to help with this. Let your doctor know about any pain you have 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. You may be prescribed medicine to take regularly to help with it. Let your doctor or nurse know straight away about any pain you have. 

Fever (high temperature) 

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 it 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. It is important to get enough rest and have a balanced diet 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. 

Changes to the liver 

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 get better after a few weeks.

Long-term side effects

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, including the liver, bowel, pancreas, stomach and lungs. This is why you are carefully assessed before treatment, and why SIRT is only administered by specialist teams. It’s important that you discuss any concerns about your treatment or its possible side effects with your doctor or nurse.

Follow-up care after SIRT

Your doctor will arrange for you to have further tests to see how well your treatment has worked. This may include more blood tests and scans. Some people need to have a second treatment. Your doctor will let you know if this is necessary.

SIRT with chemotherapy

SIRT can be given in combination with chemotherapy. Giving the treatments together may be more effective, but it may also increase some of the side effects, including an increased risk of infection. Your doctor will let you know if SIRT with chemotherapy is 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 metastases from cancer of the large bowel. Your doctor will tell you if this trial is suitable for you.

Contraception and fertility issues

It’s not advisable to become pregnant before having SIRT, as it may harm the developing baby. 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 for men and women.

Back to Internal radiotherapy explained


Brachytherapy treats cancer by placing a high dose of radiation directly inside or near to the tumour.


Radioisotope therapy targets cancer cells with a radioactive liquid.