SIR sphere treatment is a minimally invasive treatment offered for patients with liver tumours arising in the liver or that have spread to the liver from other places in the body such as the bowel or breast.
Tiny microspheres containing radiation are delivered through the arteries directly into the liver and concentrate within the liver tumours. They then deposit radiation into the tumours over the following months.
Liver tumours are uniquely suited to this type of (arterial) therapy due to the fact that the normal liver has a dual blood supply from both the artery and the portal vein. Normal liver is supplied mostly by the veins and liver tumours are supplied mostly from the artery. Therefore treatments delivered into the artery target the tumour and tend to spare the surrounding liver.
Tumours treatment options include surgery, radiation and chemotherapy. SIR spheres are an appropriate choice of treatment for patients who are not currently candidates for surgical removal or ablation of their tumour(s). In patients with liver failure, liver function may not be adequate to cope with SIR sphere therapy. The best choice of therapy is usually chosen by discussion or team meeting between surgeons, oncologists and radiologists, taking into account the patient’s preferences.


The Procedure:

SIR therapy is performed in a radiology x-ray suite. On average a treatment consists of two 2 hr procedures. Local anaesthetic and twilight anaesthesia is normally administered. You can expect to feel a brief sting from local anaesthesia and then the procedure itself is normally not painful. You will be awake and able to talk and ask questions. You may feel completely normal or slightly sleepy/relaxed due to the twilight medications.
The procedure is performed via a small tube normally via the right groin. A thin plastic tube is guided via xray control through the arteries into the liver artery and an even finer tube is used to access blood vessels inside the liver. A map of the blood vessels including the tumour is then taken using injections of iodine dye (the same dye as used in CT scans) and the treatment planned.
In the first session, any blood vessel branches that lead away from the liver will be blocked using small coils. This is to reduce the risk of spheres travelling outside of the liver. This blockage is painless and safe. The first session is a “test run” wherein a harmless test dose of radiation is injected into the liver and the procedure is completed. A nuclear medicine scan is then performed (which takes about one hour) to check the test dose has been delivered safely and effectively. This also allows the dose of therapy to be planned. You will be asked to lie in bed for about 4 hrs and can normally go home the same day.

The second treatment session is planned for 2-3 weeks after the first and is much the same from the patient perspective. The same arteries are accessed and additional blocking is occasionally required. The dose of SIR spheres is then injected over about half an hour and the treatment is finished. Once again a nuclear scan is performed, this time to assess the treatment dose itself. This time an overnight stay in hospital is planned for monitoring and any medications that may be needed.

Some useful resources:

UK based SIRT info page