About SIRT

SIR-Spheres microspheres are an innovative means of treating liver cancer. In cases where it is not possible to surgically remove the liver tumors, SIR-Spheres microspheres can be used to deliver targeted, internal radiation therapy directly to the tumor. 

This new therapy is called Selective Internal Radiation Therapy also known as SIRT. This technique uses millions of tiny polymer beads or microspheres which contain a radioactive element called yttrium-90. SIR-Spheres microspheres are very small, approximately 32 microns in size and are about one-third the diameter of a strand of hair. SIRT is usually administered as an outpatient procedure by a specially trained physician known as an interventional radiologist. A small catheter is guided into the liver and the SIR-Spheres microspheres are infused through the catheter. The microspheres with the radioactive yttrium-90 are carried by the bloodstream directly to the tumors in the liver where they preferentially lodge in the small vessels feeding the tumor and deliver their dose of radiation. Unlike conventional external beam radiation, which can only be applied to limited areas of the body, SIR-Spheres microspheres selectively irradiate the tumors and therefore have the ability to deliver more potent doses of radiation directly to the cancer cells over a longer period of time.

SIR-Spheres microspheres were developed in the 1980s in Perth, Western Australia. Since then, the product and the procedure has been refined and many hundreds of patients have been treated. SIR-Spheres microspheres received PMA approval by the Food and Drug Administration (FDA) in 2002.

SIR-Spheres microspheres at Work    
How are the Microspheres Administered?   
SIRT: Treatment Options    
Do I Qualify for the SIRT treatment?    
What are the SIRT Side Effects?    

SIR-Spheres microspheres at Work     
Radiation is an effective agent for destroying tumors and is widely used in cancer treatment. However, organs in the body are sensitive to radiation and high doses can seriously affect or injure a patient. SIR-Spheres microspheres and the SIRT technique enables specific targeting and destruction of the tumors within the liver, while sparing the normal healthy tissue. Scientists and doctors at Sirtex understood that liver tumors are hypervascular and derive most of their blood supply from the hepatic artery while healthy liver tissue is fed predominantly by the portal vein. By administering the SIR-Spheres microspheres into the hepatic artery they are carried preferentially to the tumor thereby sparing the normal liver. Once infused into the hepatic artery, SIR-Spheres microspheres travel in the bloodstream to the tumors, where they become lodged around the tumors. The dose of radiation from the SIR-Spheres microspheres in conjunction with their proximity to the tumor, destroys the tumor and preserves the healthy liver tissue. The SIRT procedure allows a more pin-pointed delivery of radiation to liver tumors than other radiotherapy techniques, making it more effective in killing the cancer.

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How are the Microspheres Administered?    
SIR-Spheres microspheres are administered by a specially trained interventional radiologist. Your individual treatment plan will be reviewed by other specialists experienced in the treatment of liver tumors. The procedure is usually performed as an outpatient procedure under local sedation in the radiology suite. A small incision will be made in the patient's groin and a flexible catheter will be guided into the liver under x-ray vision. The catheter is moved through the hepatic artery and positioned by the interventional radiologist to allow for targeted infusion of the SIR-Spheres microspheres to the liver tumors. SIR-Spheres microspheres take about 15 minutes to be infused and the whole procedure takes about one hour from beginning to end.

After the procedure is completed you may be sent to have a special scan to check the level of radioactivity of the SIR-Spheres microspheres in your liver. You will be monitored for a few hours after the procedure and most patients are discharged within 24 hours. There are few precautions you and your family need to keep in mind the first week after treatment, with SIR-Spheres microspheres; there should be no close physical contact with others for longer than 2 hours, the patient should sleep in bed alone, there should be no contact with pregnant family members and children and pets should not sit on the patients lap. After a week the patient will be able to resume normal contact with family members.

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SIRT: Treatment Options     
SIR-Spheres microspheres therapy is regarded as a regional treatment; that is, the anti-cancer effect is concentrated in the liver and there is no effect on the cancer at other sites. SIR-Spheres microspheres are used to treat secondary liver cancer where the cancer originates in the bowel (colon) and then spreads to the liver. This type of cancer is called metastatic colorectal cancer. SIR-Spheres microspheres is generally not regarded as a cure, but has been shown to shrink the tumors more than chemotherapy alone. Quality of life can improve, and life expectancy may increase. For a small number of patients, treatment with SIR-Spheres microspheres can cause marked shrinkage of the liver tumor allowing for surgical removal at a later date.

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Do I Qualify for the SIRT treatment?
Patients suitable for treatment with SIR-Spheres microspheres need to establish that they      

• Have inoperable metastatic colorectal cancer, that is, cancer that originated in the bowel and has spread to the liver.
• Have the liver as the major site of disease
• Have sufficient remaining healthy liver still functioning satisfactorily (this can be determined by a simple blood test)
• Meet the pre-selection criteria established by the doctor's pre-treatment testing
• An angiogram will be needed to determine that the liver's vasculature is acceptable to receive SIR-Spheres microspheres.

Basic testing generally includes standard blood tests and a chest X-ray or CT scan of the chest to rule out cancer in the lungs

If you meet the criteria outlined then you may be a candidate for treatment. Here's what you can do: contact a treatment center in your area that specializes in SIR-Spheres microspheres therapy. A cancer specialist will then make a decision on your suitability for treatment. We will provide all the scientific and clinical information needed for your doctor to assist you in making a decision.

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What are the SIRT Side Effects?   
Patients should not have any serious side effects when SIR-Spheres microspheres are correctly administered and do not lodge outside the liver. However, during the infusion of the SIR-Spheres microspheres you may experience some pain. If you do, your doctor will provide medication to help alleviate any discomfort during the infusion. Sometimes patients develop pain in the abdomen that may last for a few hours after the administration of SIR-Spheres microspheres, but this also can be treated with medication. Some patients develop a fever that may last for up to a week. Some patients may develop nausea, but this subsides with time and medication. Most frequently, many patients feel lethargic with a poor appetite for several days after the treatment, but this also subsides with time. Patients are often placed on medication for the first month after treatment with SIR-Spheres microspheres to prevent gastritis and peptic ulceration.

There is always the potential of serious side effects if the SIR-Spheres microspheres are incorrectly delivered into the artery supplying blood to the liver. In this case, the SIR-Spheres microspheres could be inadvertently supplied to the stomach, duodenum, pancreas or other organs, resulting in very severe and even fatal side effects. Radiologists delivering SIR-Spheres microspheres are given special training to inform them of this risk and to prevent this from happening. The dose of radiation is individually prescribed for each patient. If the dose is too high, some patients could develop long-term damage to the normal liver.
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