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Selective Internal Radiation Therapy (SIRT)
SIRT is a way to use radiotherapy to treat liver cancer that cannot be removed with surgery or local ablative techniques. The radiation is delivered into or close to the tumour(s), rather than delivered from outside the body. This form of treatment is also called micro-brachytherapy.

How does SIRT work?
Radiation is an effective way to destroy tumour tissues and is used widely in cancer treatment. However, the organs and tissues in the body are sensitive to radiation and may also be damaged by radiation treatment. Thus, conventional radiotherapy (external beam radiation delivered from outside the body) can only be given to limited areas of the body.

SIR-Spheres microspheres used in SIRT are extremely small (32 microns; about one-third the diameter of a strand of hair) resin beads which contain the radioactive substance yttrium-90 (Y-90). Because of their small size, the microspheres enter the small blood vessels of the tumour where they get permanently lodged and deliver their radiation dose to an area of about 2–3mm around where they are trapped.

The microspheres only stay radioactive for a limited time. After 2 weeks only 3% of the initial radiation remains and after 1 month it all has decayed. The decayed resin microspheres stay in the liver permanently. They are harmless.


How is SIRT given?
Microspheres are delivered directly into the liver artery via a catheter. This is done by an Interventional Radiologist who is experienced in the treatment of liver tumours with this technology. You will need to attend for a pre-treatment day for some tests to allow planning your ideal treatment. You will then attend again, usually 1–2 weeks later, for treatment with SIRT.

1. The pre-treatment day
On the pre-treatment day you will usually have different tests done including an angiogram and a scintigraphy scan. You can usually go home on the same day.

a. Angiogram
You will have an angiogram on the pre-treatment day. The angiogram shows the blood supply to the liver and is used to check your liver artery. This can vary between people. Your doctor may choose to block some vessels to stop microspheres being delivered to the wrong tissue.

Before the angiogram, the groin area is numbed with a local anaesthetic. A small cut is made in your groin and a soft, flexible catheter is inserted through the cut into where it can be directed into your liver artery. Once the catheter is in place, a contrast medium is injected through the catheter and images of blood vessels are captured using x-rays. The procedure usually takes about 30–60 minutes but can take longer in some cases. It usually involves little discomfort.

b. Scintigraphy (lung-shunting scan or MAA scan)

Scintigraphy is an imaging method that uses radioactive materials called radiopharmaceuticals or radiotracers as a dye. In an MAA scan, the radiotracer MAA is injected into the catheter that has been positioned in your liver artery. This radiotracer imitates the SIR-Spheres microspheres and allows your doctor to predict where they will lodge on the day of treatment. You will need to remain still for the brief periods of time while the images are taken.


2. The treatment day
Usually, you can have SIRT as an outpatient or you may need to stay in hospital overnight.

On the treatment day you will have another angiogram. This angiogram is usually quicker than the pre-treatment angiogram because the doctor already knows exactly where to place the catheter to reach your liver artery.

Once the catheter placement is confirmed, the SIRT can be given. This takes about 15–20 minutes and the entire procedure lasts approximately 1 hour from beginning to end. You will not need an anaesthetic but you will be given a sedative to help you relax and you will be given pain relief if you need it. You may be given anti sickness medicine if you need it.

After the SIRT has been delivered, the catheter is removed. You will have a small dressing placed over the wound and pressure will be applied to the site for 10–15 minutes. You will be asked to lie still for about 4 hours to prevent bleeding. You will need to stay to be monitored for at least a few hours afterwards.

Post Delivery
All patients are admitted for overnight observation, with most being discharged the next day.

What can I expect to happen after treatment with SIRT?
Side effects of SIRT are usually mild. You may have pain in your abdomen or nausea for 1–2 days. You also may have a raised temperature, chills or a feeling of pressure in the abdomen. These side effects are usually gone in a few days. Tiredness and appetite loss are the most common side effects and can last for up to 6 weeks.

You will need to take a few precautions after receiving SIRT. This is to minimise the chances of exposing other people to radiation. All radiation will have been dissipated within 4 weeks.

As with any other treatment options used to extend the survival of patients with cancer, SIRT can cause severe side effects which in rare cases can lead to death. The risk of these more serious side effects from SIRT is small. It can happen if the microspheres are mistakenly delivered to the stomach, duodenum (small intestine), pancreas or other organs.

You will be treated by a doctor who is specially trained to deliver SIRT and to minimise the risk of these things happening. However the risk cannot be eliminated.