SIR-Spheres Microspheres

FDA-Cleared Indications

• The FDA record describes the addition of a new cleanroom, two production hot cells, and associated equipment to existing manufacturing space.
• SIR-Spheres microspheres are indicated under their product labeling for selective internal radiation therapy of certain liver tumors, including unresectable metastatic colorectal cancer and hepatocellular carcinoma.

Clinical Applications

• Radioembolization of unresectable metastatic colorectal cancer involving the liver
• Radioembolization of hepatocellular carcinoma involving the liver
• Selective delivery of yttrium-90 radiation to liver tumors through catheter-based hepatic arterial treatment
• Treatment planning and administration in appropriately selected patients when liver-directed radiation is part of the oncology treatment plan

Reported off-label uses

• Radioembolization for other primary or metastatic liver tumors not specifically included in the applicable labeling
• Lobar or segmental radioembolization strategies used in selected liver tumors outside the labeled indication

Off-label use: these uses are reported in practice or the literature but are not part of the FDA-cleared indications. Physicians may use a cleared device off-label based on their medical judgment; the manufacturer may not promote off-label uses.

Practical Considerations

• Treatment requires angiographic mapping of the hepatic arterial anatomy, assessment of tumor blood supply, and evaluation for vessels that could carry microspheres to the stomach or other non-target organs.
• The microspheres are administered through a catheter placed in a hepatic artery, usually through femoral or radial arterial access, under fluoroscopic imaging; radiation-safety handling and specialized preparation are required.
• Patients need adequate liver function and must be assessed for factors such as excessive lung shunting, significant non-target arterial flow, uncontrolled infection, or a high risk of radiation-induced liver injury.
• SIR-Spheres are resin microspheres containing yttrium-90; they are not permanent mechanical implants, but the radioactive yttrium decays over time and the microspheres generally remain in the treated vascular bed.
• MRI safety and image-artifact information should be confirmed in the current manufacturer’s instructions for use and facility protocol; the treatment is planned with angiography and nuclear medicine imaging rather than MRI alone.