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Selective Internal Radiation Therapy (SIRT)

Overview

Selective Internal Radiation Therapy (SIRT) is a procedure for oncology (cancer) patients to treat liver tumours using tiny radioactive beads. After SIRT, most patients see a reduction or stabilisation of their liver tumours. Having this treatment can increase survival time, but is not a permanent cure.
 

What is SIRT?

SIRT 1SIRT provides treatment for liver tumours by direct delivery of tiny radioactive microscopic beads to the tumour site. These microspheres or beads are called SIR-Spheres®. SIR-Spheres® release radiation energy called “Beta” radiation, a common type of radiation also used in other nuclear medicine therapy.

SIR-Spheres® are approved for the treatment of liver tumours that cannot be removed by surgery. These could be primary liver cancer (tumours local to liver) or secondary tumours that have spread from other parts of the body to liver.

Cancer cells need oxygen and blood supply to grow. These tiny microspheres are lodged directly into the blood supply feeding these tumours. The radiation given by beads destroys these blood vessels stopping blood and hence oxygen and nutrient flow to tumours.

The radiation given off by the beads extends to an area of about 4mm which means that there is little damage to healthy tissue in the liver and no significant level of radiation outside the body.  The radioactivity of the beads decreases quickly, and its treatment effect occurs mainly within the first two days.

For more information regarding the SIR-Spheres®, please refer to the SIRTeX website.
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How is SIRT performed?

The procedure will be conducted in an angiography suite (“cath lab”) at Mercy Angiography, which is in the Mercy Hospital at 98 Mountain Road, Epsom in Auckland. Your Interventional Radiologist will be assisted by nurses and other highly trained staff.

SIRT normally involves two separate procedures. The first procedure is a preparation or work-up stage and in the second phase delivery of SIR-Spheres® occurs.

Preparation ("work-up") - Stage 1

SIRT 2You will be awake during the procedure but may be lightly sedated. Your groin will be numbed with local anaesthetic before the catheter is introduced. You should not feel pain at the entry site but there still may be some non-painful sensations such as pressure. You cannot feel the catheter moving inside your arteries.

A tiny plastic tube called a catheter is introduced under local anaesthesia through a tiny incision (less than 6mm) in the groin. Your interventional radiologists watches the catheter on an x-ray screen as he passes the tip of the catheter through your femoral artery guiding it to arteries supplying your liver. A special fluid (contrast or dye) is injected and a movie picture is recorded as the dye flows into the artery and its branches and makes them visible on the fluoroscope's monitor.

The contrast media makes vessels supplying the tumour "light up". The interventional radiologist identifies and maps the vessels leading to and from the tumour. Once vessels leading to other body parts (stomach or intestines) from the liver are identified he then injects the branches with tiny particles or coils to block those branches, thereby reducing the possibility of the radiation spheres affecting other organs of the body.

The radiologists then inject a small amount of radioactive spheres (MAA) which is called a tracer and acts in similar manner to the SIR spheres®. Following this, you will be transferred to NZ Medical Imaging for a scintiscan scan for the tracer to observed and to predict the behaviour of the actual SIR spheres® when they are injected.

After the scintiscan you will be observed for 4 hours before being discharged.

Following the phase I procedure, your doctors study the x-ray images and scintiscan scan reports to determine suitability for you to receive SIR spheres®.

Delivery of SIR Spheres - Stage II

This stage II procedure usually takes about 7 to 10 days after the work-up stage.  The second procedure is exactly like the first procedure with the exception of the SIR spheres®. Again you will be awake during the procedure. You will be given some relaxing medications during the procedure. Access to your liver artery will be done the same way as your initial procedure where the radiologists numbs your groin with local anaesthetic and introduce a plastic tube through tiny incision in the groin.
 
Under x-ray guidance the plastic tube (catheter) is passed through the femoral arteries to be positioned in the liver arteries close to the liver tumours. Once in position, the SIR spheres® are infused through the catheter into the arteries. The SIR spheres® are prepared by Nuclear Medicine and brought to Mercy Angiography in a special Perpex box on the day of your procedure. The catheter is then connected to the Perpex box to begin infusion. The radiologists inject contrast media in between infusions to check the position of the catheter.

Once infusion is complete, the catheter is removed. Pressure is applied for approximately 10 minutes on the groin to stop bleeding. During infusion you may experience slight pain or nausea. In these instances you will be given medications to make you as comfortable as possible.
 
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How should I prepare for SIRT?

Your doctor will arrange some of the following tests to determine whether SIRT is suitable for you:

Blood Tests
These can include a full blood count and certain tumour markers together with a kidney and liver function tests.

Other Tests
Your doctor may also do a CT scan, MRI or PET (Positron Emission Tomography) scan to determine blood supply to the tumours and determine how much liver is affected by the tumours.

Your procedure will be done in 2 stages. A “work up” stage to prepare you for SIRT delivery and a second stage of “SIRT delivery”. You will need to do the following prior to each of your two procedures:

Fasting: You will likely be instructed not to eat or drink anything 2 hours prior to your procedure. You may continue to drink clear fluids. Your doctor will tell you which medications you may take on the morning of your procedure.
Allergies or previous reactions to contrast (X-ray dye): Please inform Mercy Angiography staff at the time of booking your procedure if you have any known history of allergies, particularly allergies to x-ray contrast and seafood.
Diabetes: If you are a diabetic you should inform your doctor at the time of booking. You may need to discuss your insulin dose with your radiologist.
Medications: Please inform your doctor about all the medication you are taking. You doctor may advise you to stop taking some medications temporarily a few days prior to your procedure e.g. blood thinners.

Please bring any medication and any recent blood test results with you on the day of your procedure.
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What happens after the Stage II procedure?

  • The catheter is removed and pressure is applied to your groin to stop bleeding.
  • Your radiologist will discuss the findings with you or at a follow-up appointment.
  • You will be transferred to the ward where you will be monitored overnight.
  • You should be discharged after an overnight stay in the hospital.
  • You may experience some pain or nausea following the infusion of the SIR spheres®. Patient have varying responses to the SIR infusion. You will be given medication if necessary to help manage this.
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What are the side effects?

Individual patients react differently to SIRT. Some may experience fewer side effects while others may experience more. The side effects are temporary and disappear with time. Some common side effects are:
 
  • Nausea (this a temporary effect and can be controlled with anti-nausea medication)
  • Abdominal pain
  • Reduced appetite
  • Tiredness
  • You could experience a short-term fever as the radiation destroys the tumour cells.
  • As you have radiation in the body from SIR, it is advised to avoid long physical contact with children and pregnant women initially.
 
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What are the Risks and Benefits?

The interventional radiologists doing these procedures are highly trained specialists which helps keep the risks to minimum.

Risks

  • Complications can arise if SIR spheres® get unintentionally delivered to the stomach (causing stomach ulcers), pancreas (causing acute pancreatitis) and gall bladder causing inflammation.
  • Liver hepatitis can also occur due to too much radiation as a result of poor liver function because of the tumour. Patients who are at risk of this will be advised against SIRT treatment.
  • A small amount of bruising at the catheter entry point is relatively common. This is not usually clinically important unless it comes more painful. Sometimes a “false aneurysm” or out-pouching of the groin artery can occur deep under the skin at the puncture site. This shows up as increasing pain at the puncture site. The diagnosis is made by ultrasound test and treatment is usually by an injection.
  • An allergic reaction to contrast media (dye) can sometimes occur causing a rash and itchiness. Exceptionally rarely a very severe life threatening allergic reaction can happen. The x-ray contrast may cause some damage to kidneys - this is usually temporary and is more common in patients who already have damaged kidneys or who suffer from diabetes.

Benefits

  • Studies have shown that SIRT has greatly benefited the survival rates of the cancer patients if used together with standard chemotherapies. It has also helped in reducing the size of the tumour, which in some cases enables a surgeon to surgically extract them from the liver.
Risk and benefits of these procedures will vary between individual patients. Some patients may benefit more than the others.
 
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