Selective internal radiation therapy for secondary bowel cancer

• What Selective Internal Radiation Therapy (SIRT) is
• How SIRT works
• Which cancers SIRT can treat
• Research into SIRT
• How you have SIRT

SIRT stands for Selective Internal Radiation Therapy. It is a new way of using radiotherapy to treat liver cancers that can’t be removed with surgery. SIRT is internal radiotherapy, which is also called brachytherapy. Your doctor inserts a thin tube called a catheter into the hepatic artery. This is the main artery that supplies blood to the liver. They then send tiny beads called microspheres down the catheter and they get stuck in the small blood vessels around the tumour. The microspheres contain a radioactive substance which give a dose of radiation to the tumour. The microspheres are also called ‘SIR-spheres’, and the radioactive substance is called ‘yttrium 90’.

The radiation from the microspheres damages the tumours’ blood supply, so the tumours can’t get the nutrients they need. This process is sometimes called radioembolisation. The radiation also damages the DNA of the cancer cells, which stops the cancer cells growing.

The microspheres give off radiation to an area only 2 to 3mm around where they are trapped. This means they cause very little damage to the surrounding healthy tissue. The microspheres only stay radioactive for 10 to 14 days but remain in the liver permanently. They are harmless.

Doctors only use SIRT if they cannot remove the tumours with an operation. They have looked at how well this treatment works for both primary and secondary tumours of the liver, including

• Advanced bowel cancers that have spread to the liver
• Cholangiocarcinomas
• Hepatocellular cancers
• Secondary neuroendocrine tumours that have spread to the liver

The National Institute for Health and Clinical Excellence (NICE) has reviewed SIRT and in 2011 advised that

• SIRT is safe to use
• Research has shown that SIRT can reduce the size of liver tumours
• SIRT can be used to treat people who can’t have surgery

Their guidance said that we need more research to see if SIRT can help people live longer and reduce symptoms.

A phase 1 trial in 2007 used SIRT to treat people whose bowel cancer had spread to their liver. The researchers treated the people in the trial with SIRT along with FOLFOX chemotherapy.

As this was a phase 1 trial, the researchers were mainly trying to find out

• How safe it was to combine these two treatments
• What the doses should be

The results from this trial showed that the combination treatment was safe. They also suggest that the people who had the combination treatment were free of cancer for longer than people who had chemotherapy alone. However, as this was a small, early trial, we need further research to confirm these results. A phase 3 trial called FOXFIRE is testing SIRT in combination with chemotherapy. You can find out more about this trial on our clinical trials database.

You may have SIRT on its own or with chemotherapy.

Before you can have the SIRT, you have an angiogram. This is to look at the blood supply to the liver and to check your hepatic artery. This can vary between people. Occasionally people can't have treatment because their hepatic artery also supplies blood to their lungs or other sensitive tissue. This means that the SIRT microspheres could reach these areas and damage them.

Immediately before you have the treatment you will have

• A sedative to relax you
• Anti sickness medicine
• Antibiotics

Then the doctor gives you an injection into your groin to numb the area. Once the area is numb they make a tiny cut in the groin and put a fine tube called a catheter into the artery in the groin (the femoral artery). Using scans the doctor passes the catheter up the femoral artery and into the hepatic artery. Once this is in place the doctor gives the treatment. The whole process takes about an hour.

After the treatment you will have a dressing put over the small wound. Most people need to stay in hospital overnight. Your doctor will give you painkillers and anti sickness medicine to take if you need it.

Generally the side effects are mild. They include a raised temperature, chills, nausea, and a stomach ache or a feeling of pressure in the abdomen. These side effects are usually gone in a few days. Tiredness may last for a couple of weeks.

Some research shows that people who had SIRT had a fall in the number of white cells in the blood. White cells help the body fight infection. As SIRT is often given with other treatments we need more research to find out exactly how and why this happens. More rarely, people have had inflammation of the liver.