Selective Internal Radiation Therapy (SIRT), also known as Radioembolization, is a liver-directed therapy for inoperable liver tumors. SIRT is typically a 2-stage process. It requires the involvement of a multi-disciplinary team consisting of representatives from most, if not all of the following specialities: Medical Oncology, Surgical Oncology, Gastroenterology / Hepatology, Nuclear Medicine, Interventional Radiology and Radiation Safety.
A microcatheter is used to deliver millions of radioactive microspheres into the hepatic artery, where they are carried into the arterioles and selectively lodge in the tumor microvasculature (for further information see Mode of Action).
The SIRT procedure targets liver tumors directly and enables high doses of radiation to the tumor tissue by using the special tumor's blood supply. Healthy liver tissue derives up to 90% of its blood from the portal vein, with only a small amount of the blood coming from the hepatic artery. In contrast, liver tumors derive up to 90% of their blood from the hepatic artery since they need a profuse supply of highly oxygenated blood. The hepatic artery therefore provides an ideal channel for a targeted tumor treatment.
- Increase the time to progression
- Extend overall survival
- Potentially downsize or downstage tumors for liver resection, ablation, or transplantation
- Provide palliation of symptoms
SIRT can be combined with modern chemotherapy or administered as a monotherapy, either during a chemotherapy-free interval, in a salvage setting or as an alternative to local or systemic treatments.