Selective Internal Radiation Therapy (SIRT)
Intra-arterial radiation therapy is an innovative means of treating liver tumors.
In cases where it is not possible to surgically remove the liver tumors, radioactive
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.
How Does SIRT Work?
When tumors arise in the liver, their blood supply is derived from the hepatic artery;
in contrast, normal liver tissue receives about 80% of its blood supply from the
portal vein. SIRT takes advantage of this knowledge by using the portal vein as
a direct route to deliver yttrium-90 radiation microspheres directly into the liver
tumors. By selectively infusing radioactive material into the left, right or common
hepatic artery, a concentrated dosage can be delivered directly into the tumor,
while conserving normal liver tissue that surrounds the tumor.
These microspheres are very small, approximately 32 microns in size, and are about
one-third the diameter of a strand of hair. SIRT is 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 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, SIRT 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.
There are currently two types of SIRT yttrium-90 microspheres that have been FDA
approved for treatment of liver tumors. Therasphere® uses glass beads to deliver
yttrium-90 radiation and Sir Spheres® uses resin beads. At Norton Healthcare, we
offer both of these innovative procedures. Our liver cancer specialists work with
the interventional radiologists, the radiation oncologists and the nuclear physicists
to customize therapies and determine which treatment option offers the most benefit
to the patient.
To see more, view the video clips below: