Selective internal radiation therapy (SIRT) is a way of giving radiotherapy treatment for cancer in the liver.
What selective internal radiation therapy (SIRT) is
SIRT is a way of using radiotherapy to control liver cancers that can’t be removed with surgery. It is a type of internal radiotherapy. It is sometimes called radioembolisation.
You have tiny beads called microspheres put down a thin tube into the main blood vessel that supplies blood to your liver (the hepatic artery). Each bead is smaller than the width of a human hair. They get stuck in the small blood vessels around the tumour.
The microspheres contain a radioactive substance. The radiation travels a short distance to treat the cancer. The microspheres are also called SIR-spheres or TheraSpheres.
How SIRT works
The microspheres block the small blood vessels around the liver tumour and reduce the blood supply. So the tumour can’t get the nutrients it needs to grow.
The radiation from the microspheres destroys the tumour cells.
The microspheres give off radiation to an area a few millimetres around where they are trapped. This means they cause very little damage to the surrounding healthy tissue.
Who can have SIRT?
SIRT is available on the NHS in England, Scotland and Wales through the Commissioning through Evaluation (CtE) programme.
The programme aims to increase access to services and treatments that aren't routinely funded by the NHS. SIRT can be used within the NHS for:
- bowel cancer that has spread to the liver
- bile duct cancer (intrahepatic cholangiocarcinoma)
At the moment, SIRT is only for people who can’t have surgery and the cancer hasn't responded to chemotherapy.
You must be well enough to have SIRT and your liver must be working well. You can be referred to a specialist centre if your specialist thinks SIRT is a suitable treatment for you.
If you have primary liver cancer (hepatocellular carcinoma) that can’t be removed with surgery, you might have SIRT as part of a clinical trial.
If you can't take part in a trial, or you have another type of cancer that has spread only to the liver, your specialist might apply for funding to see if you can have the treatment within the NHS.
If you have private medical insurance, the insurance company may fund SIRT.
Tests before SIRT
Before you have SIRT, you have tests to assess your liver and plan your treatment.
A CT scan shows where the tumours are in your liver and their size. So your doctor can check that SIRT is a suitable treatment. You might not need another CT scan if you have recently had one for something else,
You will have blood tests to check:
- the number of different blood cells (a full blood count)
- how well your kidneys and liver are working
- there are no problems with your blood clotting
A planning angiogram
An angiogram looks at the blood supply to the liver, which varies from person to person. The doctor (called an interventional radiologist) blocks off tiny blood vessels that lead to other areas of the body like the stomach or lungs. This stops the SIRT microspheres from travelling to other areas of the body and damaging healthy tissue.
First you might have some sedation to help you relax. Then you have an injection of local anaesthetic to numb the area at the top of your leg (the groin). The doctor makes a small cut and puts a thin tube (called a catheter) into a blood vessel called the femoral artery.
Using x-rays, the doctor guides the catheter into your liver. They then inject a dye to show up the blood vessels. They can see the images on a screen. The dye might make you feel warm for a few seconds and you might feel as though you need to pass urine.
The doctor can see if there are blood vessels that lead to other areas of the body and can block them. This doesn’t harm the areas that these small blood vessels go to. The procedure might take 60 to 90 minutes but can take longer.
Lung shunting scan
After the angiogram, the doctor injects a radioactive tracer into the catheter. The tracer is similar in size to the SIRT microspheres.
You then have a scan that picks up the radioactive tracer. This is called a lung shunting scan or scintigraphy. This takes about an hour. It shows where the microspheres will go when you have the treatment. This helps your doctor to work out if it is safe to go ahead with the treatment.
You need to lie flat for several hours after these tests. This helps the wound in your groin to heal. You can usually go home at the end of the day or the following morning.
How you have SIRT
You have SIRT about 1 or 2 weeks after the planning angiogram. You might have it on its own or with chemotherapy.
To have SIRT you have another angiogram. When the catheter is in the right place, the doctor slowly injects the microspheres into your liver. The whole process takes about an hour.
After the treatment you have a dressing over the small wound. You need to lie flat for a few hours to allow the wound to heal properly. Most people need to stay in hospital overnight. Your nurse will give you painkillers and anti sickness medicines if you need them.
Side effects of SIRT
Generally the side effects of SIRT are mild. They include:
- a raised temperature
- feeling sick
- stomach ache
- a feeling of pressure in the abdomen
These side effects usually only last a few days. Your nurse will give you medicines to help. Contact your doctor or the hospital if you develop a high temperature (above 38C) as you might have an infection.
Tiredness is a common side effect and can last up to 6 weeks. This is normally mild, so you can still do normal everyday activities. Severe tiredness is quite rare. Talk to your specialist nurse if you are worried.
Irritation to the gut
Rarely, a small number of the microspheres can travel to the digestive system (gut). This can cause:
- pain in your abdomen
- feeling or being sick
- a stomach ulcer
- inflammation of the pancreas (pancreatitis)
To prevent irritation to the stomach, your doctor will give you anti ulcer medicines for around 4 weeks after treatment.
If the radioactive beads go to the lungs they can cause inflammation. This is very rare. It may cause a cough and shortness of breath. Your doctor might give you steroids to help.
Inflammation of the liver
This can affect how well your liver works, and may happen weeks after the treatment. You will have regular blood tests (liver function tests) to check this.
Your liver function might get better by itself after a few weeks. Or you may need steroids. Damage to the liver can be life threatening, but this is extremely rare.
Inflammation of the gallbladder
This is called cholecystitis. Symptoms include:
- feeling or being sick
It may get better without treatment, but in rare cases you may need surgery to remove the gallbladder.
Radiation safety after SIRT treatment
The range of radiation from the microspheres is very small. But as a precaution, you should avoid close contact with young children and pregnant women for the first 10 days after treatment.
Close contact means being within arm's length. Your doctor might also advise you not to share a bed for the first 4 days.
Your doctor or nurse will give you advice about the precautions before you go home. Most of the radiation has gone within 2 weeks. The microspheres stay in the liver permanently but they are harmless.
Your specialist will follow you up closely after treatment. How they do this varies slightly between hospitals.
You might have blood tests every week at first to check how well your liver is working. You may have a CT scan 6 and 12 weeks after treatment.
Your doctor and specialist nurse will talk to you about how often you will have check ups and scans.
Research into SIRT
Doctors have looked at SIRT for cancers that started in the liver (primary liver cancer). They have also researched it for cancers that have spread to the liver from another area of the body, such as bowel cancer and neuroendocrine tumours.
As SIRT is a relatively new treatment, doctors are still looking into:
- how well this treatment works
- how it affects quality of life
- whether it helps people to live longer
Doctors have to record and monitor the results of all SIRT treatments on the national SIRT register. Where possible, you have treatment as part of a clinical trial.