TheraSphere® Overview

What is TheraSphere®?

TheraSphere® 90Y glass microspheres are specifically engineered to deliver high doses of radiation to liver tumors while sparing normal tissue.1,2 The result is a targeted, well-tolerated therapy.34-38

Mechanism of Action
TheraSphere® is used in transarterial radioembolization (TARE), also known as selective internal radiation therapy (SIRT), a procedure in which glass microspheres containing radioactive 90Y are delivered to the tumor vasculature via transfemoral catheterization of the hepatic artery.1,2 TheraSphere® capitalizes on the uniquely organized dual blood supply to the liver, which occurs through the hepatic artery and the portal vein.39 In liver cancer, tumor blood supply is almost exclusively (80-100%) from the hepatic artery.39 In contrast, normal liver tissue receives most of its blood flow (75%) from the portal vein.40

TheraSphere® glass microspheres are minimally embolic and do not occlude macrovessels.41 TheraSphere® microspheres penetrate and lodge within the tumor arteriolar capillaries, where they emit radiation that is localized to the surrounding tumor tissue.12,41 The targeted distribution of microspheres optimizes dose exposure to the tumor while sparing normal tissue.12,35,36,41

Pre-treatment, Administration, and Post-treatment

Treatment requirements are specified within each study protocol. The following is a general overview of the TheraSphere® pre-treatment, administration, and post-treatment process.

Prior to the administration of TheraSphere®, the patient should undergo hepatic arterial catheterization using balloon catheterization or other appropriate angiographic techniques to prevent extrahepatic shunting.1,2

Following the placement of the hepatic catheter, Tc-99m MAA is administered into the hepatic artery to determine the extent of arteriovenous shunting to the lungs and to confirm the absence of gastric and duodenal flow.1,2 When the possibility of extrahepatic shunting has been evaluated and the patient has been deemed acceptable for treatment, TheraSphere® may be administered according to the study protocol.

TheraSphere® is delivered to the liver via a catheter placed into the femoral artery and guided by fluoroscopy to the hepatic artery.1,2 Using this technique, the physician directs the catheter into the diseased lobe of the liver by following the appropriate branch of the hepatic artery. Once the catheter is properly positioned, the physician infuses TheraSphere®, which localizes preferentially in the tumor.41 Precise lobar administration prevents the inadvertent flow of TheraSphere® into the gastrointestinal tract.1,2

A preassembled, single-use TheraSphere® Administration Set, consisting of a sterile disposable tubing set and empty sterile vial, is provided for each dose.1,2 The TheraSphere® Administration Accessory Kit, consisting of re-usable accessories including an acrylic box base, top shield, removable side shield, and bag hook, is supplied to new user sites.1,2

For detailed instructions on calculation of dose and TheraSphere® administration, please see the appropriate trial protocol.25,27,29

Immediately following TheraSphere® treatment, the patient should remain under observation consistent with institutional standard of care guidelines for aftercare in procedures involving femoral or brachial artery catheterization. Aftercare guidelines are subject to the policies and procedures established by radiology and radiation safety departments at each institution, as well as the study protocols.25,27,29

Because TheraSphere® treatment is directed to the liver tumor, there is minimal impact to healthy tissue.25,27,29 TheraSphere® treatment is typically well tolerated, with primarily transient and mild to moderate adverse effects such as fatigue, abdominal pain, and nausea.25,27,29 Risk of vascular stasis and gastric ulceration is low.25,27,29 Please refer to the Investigational Brochure for complete safety information.

Radioembolization with TheraSphere® is a minimally embolic therapy.41 Liver vasculature is preserved following treatment, allowing potential retreatment or alternative therapy.38

Since no significant amount of 90Y leaches from the TheraSphere® glass matrix, there is no need for special precautions in handling body fluids, nor are patient hygiene instructions required.39 In addition, secondary radiation exposure resulting from contact of patients with other individuals is below the U.S. Nuclear Regulatory Commission (NRC) threshold total effective dose equivalent of 1 mSv for administered activity up to 5.14 GBq.42 Please consult your institution for policy guidelines.

Risk Factors
TheraSphere® is suitable for patients in whom either the liver is the only site of disease or the liver is the major site of disease.1,2 The effects of TheraSphere® on tumors outside the liver has not yet been studied and is not within the scope of these clinical trials.

The principal investigator and medical staff will be provided with an Investigational Brochure outlining the comprehensive list of risk factors for TheraSphere®, as well as other agents and procedures used in these trials.