SIR-Spheres Selective Internal
Radiation Therapy

What is Selective Internal Radiation Therapy for Liver Tumors?

Selective Internal Radiation Therapy (SIRT) is a targeted treatment for liver tumors that delivers millions of tiny radioactive beads called SIR-Spheres microspheres directly to the liver tumors. SIRT is used to treat inoperable tumors from primary colorectal cancer that has spread to the liver.

How is it Performed?

To administer the SIR-Spheres, the interventional radiologist makes a small puncture, usually into the femoral artery near the groin. A small, flexible tube, known as a catheter is then guided through the artery into the liver. The SIRSpheres microspheres are administered through this catheter. The whole procedure takes 90 minutes.

The SIRT procedure enables radiation, which is often used to treat cancer, to be sent directly into the liver tumors by using the tumor’s blood supply. The normal liver tissue takes about 90 percent of its blood supply from the portal vein that flows from the intestine while liver tumors receive 90 percent of their blood supply from the hepatic artery. SIR-Spheres microspheres are targeted directly at the liver tumors via the hepatic artery, minimizing exposure to the remaining healthy liver tissue.

The majority of the microspheres are approximately 32 microns in diameter, about one-third the width of a strand of humanhair. The microspheres are small enough to flow through the hepatic arteries but they are too large to pass through small blood vessels within the tumor, where they become permanently lodged in the tumor bed.

What are the Risks?

In rare instances and even in experienced hands, there is a possibility that a small number of microspheres may inadvertently reach other organs, such as the gall bladder, stomach, pancreas or intestine. If SIR-Spheres microspheres reach these organs, they may cause inflammation of the gall bladder, stomach or intestine. These complications are rare but if they do occur, they will require additional treatment.

What are the Advantages?

Clinical data shows that when used in combination with chemotherapy, SIR-Spheres microspheres may shrink the patient’s liver tumors more than chemotherapy alone. For a small number of patients, treatment can cause sufficient shrinkage of the liver tumor to permit its removal by surgery at a later date. For a patient whose liver tumors are no longer responding to chemotherapy, SIR-Spheres microspheres have also been used successfully to shrink these tumors and extend the patient’s survival.

Is SIRT a Good Choice for Me?

Before SIRT can be offered as a treatment option, there are a number of factors that have to be considered by your physician. Most importantly, you need to have a sufficiently healthy liver that is working satisfactorily. Please talk with your physician to learn more about SIRT and if it’s a good option for you.

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