Selective internal radiation therapy (SIRT)

What is SIRT?

SIRT is a radiation treatment for cancer. In this procedure, a radiation source called yttrium-90 is administered in small beads delivered through the blood stream into the organ affected by cancer.

How does the procedure work?

First the interventional radiologist will map out the blood vessels of the organ, and may block some of them to ensure the spheres only go to the tumour. Once this is done, a catheter (small tube) is placed inside a blood vessel that goes directly to the organ affected by cancer. The interventional radiologist will guide the catheter close to the tumour and then will administer the specially prepared beads that contain the radiation. When the beads land in the tumour, they emit a form of radiation energy that kills the cancer cells over a short distance around the bead.

Why perform it?

The aim of the procedure is to cure or slow the growth of cancer. It may be performed alone or in combination with conventional therapies. It is typically used to treat cancers located in an organ, most commonly the liver. It is a local therapy, meaning it only treats cancer cells near where it is administered. Usually it is used for tumours in solid organs that cannot be treated by other means alone, though it may be used together with conventional surgery and chemotherapy.

What are the risks?

There is a risk that the blood vessel will be injured or bruised while the tube is being placed. If the beads travel to normal tissues, these tissues will be killed. When the tumour is killed, you may experience pain, fever and nausea. In unusual cases, the treated area can become infected which may require medication or another intervention.

Bibliography

1. Theysohn JM, Muller S, et al. Selective internal radiotherapy (SIRT) of hepatic tumors: how to deal with the cystic artery. Cardiovasc Intervent Radiol 2013; 36(4):1015-1022.
2. Theysohn JM, Schlaak JF, et al. Selective internal radiation therapy of hepatocellular carcinoma: potential hepatopulmonary shunt reduction after sorafenib administration. J Vasc Interv Radiol 2012; 23(7):949-952.
3. Ray CE Jr, Battaglia C, et al. Interventional radiologic treatment of hepatocellular carcinoma-a cost analysis from the payer perspective. J Vasc Interv Radiol 2012; 23(3): 306-314.