About TheraSphere^®

TheraSphere^{® 90}Y 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.⁴⁷ 

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 used in the treatment of hepatic neoplasia.⁴⁷

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 PVT^7,12,13
• Patients with liver metastases from primary cancers such as CRC and NET.⁴⁷
• 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 disease^7,8

Precautions/Warnings

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.
 

Glossary

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