About TheraSphere®

TheraSphere® 90Y glass microspheres are specifically engineered to carry far greater power than any other 90Y liver-directed cancer therapy, delivering high doses of radiation to liver tumors while sparing normal tissue.1,2 The result is a powerfully-targeted, well-tolerated therapy that may lead to patients becoming eligible for curative therapies. 3–8


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 TheraSphere® capitalizes on the uniquely organized dual blood supply to the liver, which occurs through the hepatic artery and the portal vein.9 In liver cancer, tumor blood supply is almost exclusively (80–100%) from the hepatic artery.9 In contrast, normal liver tissue receives most of its blood flow (75%) from the portal vein.10

TheraSphere® glass microspheres are minimally embolic and do not occlude macrovessels.11 Since vessel patency is maintained, subsequent arterial therapies are possible.7,11 TheraSphere® microspheres penetrate and lodge within the tumor arteriolar capillaries, where they emit lethal beta radiation that is localized to the surrounding tumor tissue.11,12 The targeted distribution of microspheres optimizes dose exposure to the tumor while sparing normal tissue.4,5,11,12

Potential Patient Populations

TheraSphere® is indicated for radiation treatment or as a neoadjuvant to surgery or transplantation in patients with unresectable HCC who can have placement of appropriately positioned hepatic arterial catheters.1 TheraSphere® treatment has shown encouraging results in particular patient types, including:

  • Patients with advanced HCC (BCLC C), with or without partial or branch portal vein thrombosis (PVT)5,13
  • Patients with intermediate HCC (BCLC B) who are poor candidates for conventional transarterial chemoembolization (cTACE) due to:
    • Large tumor size;13
    • Multifocal disease;13
    • Advanced age;13
    • Failure of cTACE;3,14 or
    • Presence of partial or branch PVT7,12,13
  • Patients who are considered ineligible for potentially curative treatment options such as RFA, transplant, or surgery, but could become eligible as a result of a reduction in tumor burden and downstaging of disease7,8


A retrospective study of 121 patients from five clinical trials has shown that the following five Pre-treatment High Risk Factors have been associated with at least 48% of all serious adverse events that were possibly related to use of the device and with 11 of the 12 deaths that were possibly related to use of the device:1

  • Infiltrative tumor type
  • "Bulk disease” (tumor volume >70% of the target liver volume, or tumor nodules too numerous to count)
  • AST or ALT >5 × ULN
  • Bilirubin >2 mg/dL
  • Tumor volume >50% combined with an albumin <3 g/dL

The physician should always take the above-noted Pre-treatment High Risk Factors into consideration for each patient when making decisions regarding the use of TheraSphere® for treatment.


ALT = alanine aminotransferase; AST = alanine aminotransferase; BCLC = Barcelona Clinic Liver Cancer; cTACE = conventional transarterial chemoembolization; HCC = hepatocellular carcinoma; PVT = portal vein thrombosis; SIRT = selective internal radiation therapy; TARE = transarterial radioembolization; ULN = upper limit of normal; 90Y = yttrium-90