Selective Internal Radiation Therapy (SIRT), also known as radioembolisation
Selective internal radiation therapy (SIRT) is a way of giving radiotherapy treatment for cancer in the liver that can’t be removed with surgery. It’s a type of internal radiotherapy, and is sometimes called radioembolisation.
Tiny spheres, which contain a radioactive substance called yttrrium-90, are passed down a thin tube into the hepatic artery (one of two arteries that supply the liver with blood). The spheres are made from either glass (TheraSphere) or resin (Sir-Spheres). The spheres form clusters in the small blood vessels around the tumour and release radiation to destroy the cancer cells. A new sphere, which delivers a different radioisotope called holmium-166, has recently come to market (QuiremSpeheres).
Before you have SIRT, you’ll have something called a planning or work-up angiogram, which looks at the blood supply to the liver. This is to make sure the SIRT spheres, known as microspheres, can’t travel to other areas of the body and damage healthy tissue. A specialist doctor (called an interventional radiologist) will insert a tube through an artery in the groin (femoral) or wrist (radial). Dye is then injected through a catheter and into the liver to show up blood vessels that lead to other parts of the body, which may need to be blocked. The procedure is performed under local anaesthetic to ensure you’re comfortable and conscious sedation may be offered. The procedure takes around 60 to 90 minutes.
After the angiogram, the doctor will inject a radioactive ‘tracer’ called technetium 99m-MAA into the catheter. The tracer is similar in size to the SIRT microspheres but is a pure gamma emitter. You then have a scan that picks up the distribution of the radioactive tracer. This shows where the spheres will go when you have the treatment and helps your doctor to work out if it’s safe to go ahead. Another work-up may be necessary if this scan demonstrates unexpected uptake, which is correctable.
You have SIRT a week or two after the planning angiogram. The treatment is again given via a catheter. When the catheter is in the right place, the doctor slowly injects the microspheres into your liver. It takes about an hour, and afterwards, if groin (femoral) access is performed, you’ll need to lie flat for a few hours so the wound can start to clot and heal. If wrist (radial) access is used, you will be able to sit up immediately following the procedure. Planning and treatment procedures may be performed as day cases but most centres require people to stay in hospital overnight and you’ll be give painkillers and anti-sickness medicines if you need them. Occasionally, the SIRT treatment is delivered in two stages with a 4 to 6 week interval between each treatment, where the right and left lobes of the liver are treated separately.
Generally the side effects of SIRT are mild. They include:
- a raised temperature
- feeling sick
- stomach ache
- a feeling of pressure in the abdomen
- mild fatigue, although you should still be able to do everyday activities.
These side effects usually only last a few days. Contact your doctor or the hospital if you develop a high temperature (above 38C) as you might have an infection.
The range of radiation from the microspheres is very small. However, you should avoid close contact (being within arm’s length) with young children and pregnant women for the first 10 days after treatment. Your doctor might also advise you not to share a bed for the first four days. All radiation will have left the body within two weeks - the microspheres stay in the liver permanently but are harmless.
Your specialist will follow-up closely after treatment. How they do this varies slightly between hospitals - your doctor and specialist nurse will talk to you about how often you will have check-ups and scans.
PLEASE NOTE: Until March 2017, SIRT was available on the NHS through clinical trials. Funding for this has now been withdrawn. There are currently no further SIRT clinical trials being undertaken in the UK, although NICE is considering whether SIRT should be provided through the NHS. The British Liver Trust will be making representation to NICE on patients’ behalf and we are keen to hear from you if you have had access to this treatment or feel it would be beneficial. Please contact our Director of Communications and Policy: email@example.com.
The treatment is currently available privately and if you have private medical insurance, the insurance company may fund SIRT.