# Yttrium-90 glass microspheres

Source: https://nuclide.cc/drugs/y-90-glass-microspheres/  
Nuclide record `y-90-glass-microspheres` (Agent). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

Microscopic glass beads containing a radioactive metal are injected into the artery that supplies a liver tumour. The beads stay in place permanently and give off radiation that fades away within about two weeks.

## Summary

TheraSphere consists of yttrium-90 fused into glass microspheres and delivered by selective internal radiation therapy (SIRT) through a hepatic artery catheter. It was marketed in the US from 1999-2000 under a Humanitarian Device Exemption (HDE H980006) for unresectable hepatocellular carcinoma (HCC), which limited annual patient numbers.

Boston Scientific (which acquired the product from BTG/Biocompatibles) received full FDA premarket approval (PMA P200029) on 17 March 2021, based on the LEGACY study, a retrospective single-arm, multicentre study of 162 patients with solitary unresectable HCC (1-8 cm). The approved indication is SIRT for local tumour control of solitary tumours 1-8 cm in diameter in patients with Child-Pugh A cirrhosis, no macrovascular invasion and good performance status. LEGACY reported an objective response rate of 72.2% by blinded independent central review and a 76.1% six-month duration-of-response rate.

A post-approval study (multi-compartment dosimetry, MCD-HCC) is ongoing, and a further PMA supplement was cleared by FDA in February 2026. Dosing uses partition-model or MIRD dosimetry to target roughly 100 Gy to the treated liver volume; the microspheres remain permanently implanted.

## Fields

- Kind: Agent
- Status: approved
- Last checked: 2026-09-22
- Also known as: TheraSphere; Y-90 glass microspheres
- Tags: radioembolisation; liver; beta emitter
- Brand: TheraSphere
- Modality: radioembolisation
- Mechanism: Insoluble glass microspheres (15-35 micron diameter) with yttrium-90 built into the glass matrix, infused through a hepatic artery catheter. The spheres remain permanently embedded in the liver and deliver beta radiation locally; about 95% of the yttrium-90 dose is absorbed within roughly 12 days given the isotope's short half-life.
- Approvals: US 2021: Selective internal radiation therapy (SIRT) for local tumour control of solitary unresectable HCC (1-8 cm), Child-Pugh A cirrhosis, no macrovascular invasion, good performance status
- Dosing: Intra-arterial infusion into the hepatic artery via catheter; Single administration per treated liver territory, individualised by partition-model dosimetry aiming for a target absorbed dose

## Sources

- FDA: TheraSphere P200029 approval page: https://www.fda.gov/medical-devices/recently-approved-devices/theraspheretm-p200029
- FDA: Summary of safety and effectiveness data (P200029): https://www.accessdata.fda.gov/cdrh_docs/pdf20/P200029B.pdf
- Boston Scientific: FDA approval press release, 18 March 2021: https://news.bostonscientific.com/2021-03-18-Boston-Scientific-Receives-FDA-Approval-for-TheraSphere-TM-Y-90-Glass-Microspheres
- LEGACY study, Hepatology 2021: https://journals.lww.com/hep/fulltext/2021/11000/yttrium_90_radioembolization_for_the_treatment_of.9.aspx

## Connected records

- drugs: [Holmium-166 microspheres](https://nuclide.cc/drugs/ho-166-microspheres/), [Technetium Tc-99m albumin aggregated (MAA)](https://nuclide.cc/drugs/tc-99m-maa/), [Yttrium-90 resin microspheres](https://nuclide.cc/drugs/y-90-resin-microspheres/)
- isotopes: [Yttrium-90](https://nuclide.cc/isotopes/y-90/)
- indications: [Hepatocellular carcinoma](https://nuclide.cc/indications/hcc/)
- technologies: [Radioembolisation (TARE / SIRT, yttrium-90)](https://nuclide.cc/technologies/radioembolisation-tare/)
- companies: [Boston Scientific](https://nuclide.cc/companies/boston-scientific/)

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