What are SIR-Spheres Microspheres?

SIR-Spheres microspheres are an innovative means of treating liver cancer. In cases where it is not possible to surgically remove the liver tumours, SIR-Spheres microspheres can be used to deliver targeted, internal irradiation therapy directly to the tumour. This new therapy is called Selective Internal Radiation Therapy also know as SIRT. This technique uses millions of tiny resin microspheres which contain a radioactive element called yttrium-90. SIR-Spheres microspheres are very small, approximately 32 microns in size. A specially trained physician known as an interventional radiologist usually administers sIR-Spheres microspheres as an inpatient procedure. 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 tumours in the liver where they preferentially lodge in the small vessels feeding the tumour 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 tumours 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 1980's in Perth, Western Australia. Many patients have been treated commercially and within a clinical trial setting all over the world (Australia, USA, Europe, Singapore, Hong Kong, New Zealand and India). SIR-Spheres microspheres has TGA approval in Australia, PMA approval by the Food and Drug Administration (FDA) in the USA and BSI approval for Europe (CE Mark).

SIR-SPHERES MICROSPHERES AT WORK

Radiation is an effective agent for destroying tumours 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 enable specific targeting and destruction of the tumours within the liver, while sparing the normal healthy tissue. Scientists and doctors at Sirtex understood that liver tumours 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 tumour thereby sparing the normal liver. Once infused into the hepatic artery, SIR-Spheres microspheres travel in the bloodstream to the tumours, where they become lodged around the tumours. The dose of radiation from the SIR-Spheres microspheres in conjunction with their proximity to the tumour destroys the tumour and preserves the healthy liver tissue. The SIRT procedure allows a more pinpointed delivery of radiation to liver tumours than other radiotherapy techniques, making it more effective in killing the cancer.

HOW ARE SIR-SPHERES MICROSPHERES ADMINISTERED?

A specially trained interventional radiologist administers SIR-Spheres microspheres. Other specialists experienced in the treatment of liver tumours will review your individual treatment plan. 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 tumours. 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 no sit on the patients lap. After a week the patient will be able to resume normal contact with family members.

SELECTIVE INTERNAL RADIATION THERAPY (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 (metastatic colorectal cancer) as well as primary liver cancer (HCC) where the liver is the primary site. SIR-Spheres microspheres is generally not regarded as a cure, but has been shown to shrink the tumours more than chemotherapy alone or in combination with systemic chemotherapy. Quality of life can improve, and survival benefit (life expectancy) may increase. For a small number of patients, treatment with SIR-Spheres microspheres can cause marked shrinkage of the liver tumour allowing for surgical removal at a later date.

HOW DO I QUALIFY FOR THE 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 or primary liver cancer (HCC),
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 vascular 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 your treating physician (eg medical oncologist) and/or contact a treatment center in your area that specializes in SIR-Spheres microspheres therapy.

WHAT ARE THE 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 can also 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.