{"entity":{"id":"y-90-glass-microspheres","kind":"drug","name":"Yttrium-90 glass microspheres","aka":["TheraSphere","Y-90 glass microspheres"],"tldr":"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.\n\nBoston 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.\n\nA 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.","status":"approved","asOf":"2026-09-22","links":[{"label":"FDA: TheraSphere P200029 approval page","url":"https://www.fda.gov/medical-devices/recently-approved-devices/theraspheretm-p200029"},{"label":"FDA: Summary of safety and effectiveness data (P200029)","url":"https://www.accessdata.fda.gov/cdrh_docs/pdf20/P200029B.pdf"},{"label":"Boston Scientific: FDA approval press release, 18 March 2021","url":"https://news.bostonscientific.com/2021-03-18-Boston-Scientific-Receives-FDA-Approval-for-TheraSphere-TM-Y-90-Glass-Microspheres"},{"label":"LEGACY study, Hepatology 2021","url":"https://journals.lww.com/hep/fulltext/2021/11000/yttrium_90_radioembolization_for_the_treatment_of.9.aspx"}],"tags":["radioembolisation","liver","beta emitter"],"related":["y-90-resin-microspheres","ho-166-microspheres","y-90"],"indications":["hcc"],"sections":[],"technologies":["radioembolisation-tare"],"targets":[],"drugs":[],"companies":["boston-scientific"],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"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":[{"region":"US","year":2021,"indication":"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"}],"mechanismSteps":[],"dosing":{"route":"Intra-arterial infusion into the hepatic artery via catheter","schedule":"Single administration per treated liver territory, individualised by partition-model dosimetry aiming for a target absorbed dose","source":"https://www.accessdata.fda.gov/cdrh_docs/pdf20/P200029B.pdf"},"toxicity":[],"access":[],"regulatoryEvents":[]},"route":"/drugs/y-90-glass-microspheres/","neighbours":{"drug":[{"id":"ho-166-microspheres","kind":"drug","name":"Holmium-166 microspheres","route":"/drugs/ho-166-microspheres/"},{"id":"tc-99m-maa","kind":"drug","name":"Technetium Tc-99m albumin aggregated (MAA)","route":"/drugs/tc-99m-maa/"},{"id":"y-90-resin-microspheres","kind":"drug","name":"Yttrium-90 resin microspheres","route":"/drugs/y-90-resin-microspheres/"}],"isotope":[{"id":"y-90","kind":"isotope","name":"Yttrium-90","route":"/isotopes/y-90/"}],"indication":[{"id":"hcc","kind":"indication","name":"Hepatocellular carcinoma","route":"/indications/hcc/"}],"technology":[{"id":"radioembolisation-tare","kind":"technology","name":"Radioembolisation (TARE / SIRT, yttrium-90)","route":"/technologies/radioembolisation-tare/"}],"company":[{"id":"boston-scientific","kind":"company","name":"Boston Scientific","route":"/companies/boston-scientific/"}]}}