Y90 Glass Microspheres
TheraSphere glass microspheres take advantage of a tumor’s hypervascularity and prioritize microsphere flow to the tumor. Because TheraSphere has high activity per sphere, fewer microspheres are needed to achieve the desired dose. The minimally embolic nature of TheraSphere preserves the patient’s vasculature and allows for safe and effective delivery of radiation without the risk of stasis and reflux and spares healthy tissue.
TheraSphere allows for personalization of treatment and greater flexibility by offering a multitude of standard and custom dose vial options to meet individual patient treatment goals. TheraSphere has demonstrated treatment success in a range of scenarios: curative or palliative, livers with single or multifocal tumors, portal vein thrombosis (PVT), and using segmental or lobar approaches1-6.
- Hilgard P, Hamami M, Fouly AE, et al. Radioembolization with yttrium-90 glass microspheres in hepatocellular carcinoma: European experience on safety and long-term survival. Hepatology 2010;52(5):1741–9
- Riaz A, Gates VL, Atassi B, et al. Radiation segmentectomy: a novel approach to increase safety and efficacy of radioembolization. Int J Radiat Oncol Biol Phys 2011;79(1):163–71
- Mazzaferro V, Sposito C, Bhoori S, et al. Yttrium-90 radioembolization for intermediate-advanced hepatocellular carcinoma: a phase 2 study. Hepatology 2013;57(5):1826–37
- Vouche M, Habib A, Ward TJ, et al. Unresectable solitary hepatocellular carcinoma not amenable to radiofrequency ablation: multicenter radiology-pathology correlation and survival of radiation segmentectomy. Hepatology 2014;60(1):192–201
- Salem R, Lewandowski RJ, Kulik L, et al. Radioembolization results in longer time-to-progression and reduced toxicity compared with chemoembolization in patients with hepatocellular carcinoma. Gastroenterology 2011;140(2):497–507
- Lewandowski RJ, Kulik LM, Riaz A, et al. A comparative analysis of transarterial downstaging for hepatocellular carcinoma: chemoembolization versus radioembolization. Am J Transplant 2009;9(8):1920–8
Mechanism of Action
A healthy liver receives most of its blood flow (75%) from the portal vein 1. In HCC, tumor blood supply is almost exclusively from the hepatic artery (80-100%) 2. Therasphere Y90 glass microspheres exploit tumor blood flow and are delivered to the tumor vasculature via catheterization of the hepatic artery.
The glass microspheres penetrate the tumor arteriolar capillaries where they emit lethal beta radiation that is localized to the surrounding tumor tissue.3,4 The targeted distribution of microspheres provides high absorbed dose coverage to the tumor while sparing normal tissue.3,4,5,6
The high specific activity of Therasphere glass microspheres means that fewer are administered to achieve the desired dose. As a result, glass microspheres are minimally embolic and do not occlude macrovessels.3 Since vessel patency is maintained, subsequent arterial therapies are possible, if needed.3,7
- Merkel C, Montagnese S, Amodio P. Functional Anatomy of Liver Circulation. Functional Molecular.
- Kennedy A, Nag S, Salem R, et al. Recommendations for radioembolization of hepatic malignancies using yttrium-90 microsphere brachytherapy: a consensus panel report from the radioembolization brachytherapy oncology consortium. Int J Radiat Oncol Biol Phys 2007;68(1):13–23.
- Salem R, Thurston KG. Radioembolization with 90Yttrium microspheres: a state-of-the-art brachytherapy treatment for primary and secondary liver malignancies. Part 1: Technical and methodologic considerations. J Vasc Interv Radiol 2006;17:1251–78.
- Kulik M, Carr B, Mulcahy M, et al. Safety and efficacy of 90Y radiotherapy for hepatocellular carcinoma with and without portal vein thrombosis. Hepatology 2008;47(1):71–81.
- Riaz A, Gates VL, Atassi B, et al. Radiation segmentectomy: a novel approach to increase safety and efficacy off radioembolization. Int J Radiat Oncol Biol Phys 2011;79(1):163–71.
- Mazzaferro V, Sposito C, Bhoori S, et al. Yttrium-90 radioembolization for intermediate-advanced hepatocellular carcinoma: a phase 2 study. Hepatology 2013;57(5):1826–37.
- Salem R, Lewandowski RJ, Kulik L, et al. Radioembolization results in longer time-to-progression and reduced toxicity compared with chemoembolization in patients with hepatocellular carcinoma. Gastroenterology 2011;140(2):497–507.
Product Specifications and Sizes
TheraSphere consists of Y90 glass microspheres used in radiation treatment for patients with hepatic neoplasia.
- Insoluble glass microspheres with a mean diameter of 20 to 30 μm
- Y90 is an integral constituent of the glass
- Pure beta emitter
- Average energy of 0.9367 MeV
- Average tissue penetration range of 2.5 mm (max. 11 mm)
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Level 1 evidence from the DOSISPHERE-01 Trial showed a 16 month overall survival improvement in hepatocellular carcinoma (HCC) patients treated with TheraSphere using personalized dosimetry compared to standard dosimetry
Presented at ASCO GI 2020
PDA: Personalized dosimetry
SDA: Standard, single-compartment dosimetry
DOSISPHERE-01 Trial: A prospective, randomized, multi-center, investigator-sponsored phase II trial that looked at HCC patients (n-56) treated with TheraSphere using either personalized dosimetry (defined as multi-compartment Y-90 distribution that targets ≥205 Gy to the index lesion and ≤120 Gy in the treated normal liver) or standard dosimetry (defined as single-compartment dosimetry of 120 +/- 20 Gy absorbed dose to the treated liver).
In the trial, TheraSphere patients treated with the personalized dosimetry approach reached an overall survival rate of 26.7 months versus 10.7 months for those patients receiving standard, single-compartment dosimetry (HR: 0.421, p=0.0118).