# Yttrium-90 resin microspheres

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

## TL;DR

Tiny radioactive beads are injected through a small tube into the artery that feeds the liver. They lodge in the tumour and give it radiation from the inside, mostly sparing the rest of the liver.

## Summary

SIR-Spheres are yttrium-90-loaded resin microspheres delivered by transarterial radioembolisation (TARE/SIRT). Yttrium-90 is a pure beta emitter with a physical half-life of about 64 hours; delivery via the hepatic artery exploits the fact that liver tumours draw most of their blood supply from that vessel while normal liver parenchyma relies more on the portal vein.

The device holds the original 2002 FDA premarket approval (PMA P990065) for unresectable metastatic liver tumours from primary colorectal cancer, given together with adjuvant intrahepatic artery chemotherapy (floxuridine, FUDR). In July 2025 the FDA approved a labelling supplement extending the indication to local tumour control of unresectable hepatocellular carcinoma (HCC) in patients with no macrovascular invasion, Child-Pugh A cirrhosis, well-compensated liver function and good performance status, making SIR-Spheres the only US radioembolisation product approved for both indications.

Dosing is individualised: activity is planned using body-surface-area or partition (MIRD) dosimetry models with pre-treatment angiography and a technetium-99m macroaggregated albumin scan to check lung shunting before the therapeutic infusion. SIR-Spheres also carry regulatory approval in the EU (2002), Canada (2016), Australia (1998) and other markets.

## Fields

- Kind: Agent
- Status: approved
- Last checked: 2026-09-22
- Also known as: SIR-Spheres; Y-90 resin microspheres
- Tags: radioembolisation; liver; beta emitter
- Brand: SIR-Spheres
- Modality: radioembolisation
- Mechanism: Biocompatible resin microspheres (20-40 micron diameter) carrying yttrium-90, a pure beta emitter, infused through a catheter into the hepatic artery so they lodge preferentially in the hypervascular tumour bed and irradiate it from within while sparing most healthy liver.
- Approvals: US 2002: Unresectable metastatic liver tumours from primary colorectal cancer, with adjuvant intrahepatic artery chemotherapy (FUDR); US 2025: Local tumour control of unresectable hepatocellular carcinoma (no macrovascular invasion, Child-Pugh A, well-compensated liver function, good performance status)
- Dosing: Intra-arterial infusion into the hepatic artery via catheter; Single administration per treated liver territory; activity individualised by body-surface-area or partition-model dosimetry

## Sources

- FDA PMA P990065/S014 approval order: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpma/pma.cfm?ID=P990065S014
- FDA: Summary of safety and effectiveness data (HCC supplement): https://www.accessdata.fda.gov/cdrh_docs/pdf/P990065S014B.pdf
- Sirtex: FDA approval for HCC indication (7 July 2025): https://www.sirtex.com/media/p1kjiw5m/sirtex-medical-announces-fda-approval-hcc-indication-us.pdf
- FDA: original SSED for colorectal indication (2002): https://www.accessdata.fda.gov/cdrh_docs/pdf/p990065b.pdf

## 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 glass microspheres](https://nuclide.cc/drugs/y-90-glass-microspheres/)
- isotopes: [Technetium-99m](https://nuclide.cc/isotopes/tc-99m/), [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: [Sirtex Medical](https://nuclide.cc/companies/sirtex/)

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