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What Is Selective Internal Radiation Therapy?

Selective internal radiation therapy is an image-guided treatment that delivers radioactive microspheres through the hepatic arteries to tumors in the liver. It is commonly abbreviated SIRT and is also called transarterial radioembolization. Most modern treatments use microspheres containing yttrium-90, or Y-90, which emit beta radiation after lodging in small tumor-feeding vessels. The technique concentrates radiation within the treated liver territory while limiting exposure to much of the surrounding body.

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What Is Selective Internal Radiation Therapy?

Selective internal radiation therapy is an image-guided treatment that delivers radioactive microspheres through the hepatic arteries to tumors in the liver. It is commonly abbreviated SIRT and is also called transarterial radioembolization. Most modern treatments use microspheres containing yttrium-90, or Y-90, which emit beta radiation after lodging in small tumor-feeding vessels. The technique concentrates radiation within the treated liver territory while limiting exposure to much of the surrounding body.

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Why Is Selective Internal Radiation Therapy Performed?

SIRT is used for selected primary and metastatic liver tumors when targeted internal radiation fits the overall cancer-treatment plan. Common indications include hepatocellular carcinoma and liver-dominant metastases from colorectal, neuroendocrine, or other cancers. It can be used for local tumor control, downstaging, bridging to transplantation, or radiation segmentectomy in carefully selected patients. Treatment decisions consider tumor distribution, liver function, vascular anatomy, prior therapy, extrahepatic disease, portal-vein status, and the expected radiation dose to healthy liver and lungs.

How Is Selective Internal Radiation Therapy Performed?

Treatment begins with mapping angiography to define hepatic arterial anatomy and identify vessels that could carry microspheres to the stomach, bowel, or other nontarget organs. A technetium-99m macroaggregated albumin study is commonly used to estimate lung shunting and help calculate a safe Y-90 activity. During the treatment session, a catheter is advanced into the selected hepatic artery and the radioactive microspheres are infused into the tumor-feeding circulation. Post-treatment nuclear imaging can be used to confirm where the microspheres deposited and support dosimetry assessment.

What Is Recovery Like After Selective Internal Radiation Therapy?

Most patients require only a short observation period and return home the same day or after brief monitoring. Fatigue, abdominal discomfort, nausea, reduced appetite, or low-grade fever can occur during the first several days. Blood tests are used to monitor liver function, and follow-up computed tomography, magnetic resonance imaging, or nuclear imaging evaluates treatment response. Additional SIRT, systemic therapy, ablation, transplantation, or surveillance depends on the tumor type and response.

What Are the Risks and Complications?

Possible complications include bleeding at the catheter site, contrast reactions, fatigue, abdominal pain, and deterioration in liver function. Nontarget microspheres can cause radiation injury to the stomach, duodenum, gallbladder, pancreas, or other tissues. Rare serious complications include radioembolization-induced liver disease and radiation pneumonitis when excessive activity reaches the lungs. Careful mapping, personalized dosimetry, and selective catheter placement are used to reduce these risks.

Frequently Asked Questions About Selective Internal Radiation Therapy

Is SIRT the same as Y-90 radioembolization?

Yes. SIRT commonly refers to transarterial radioembolization with yttrium-90 microspheres for selected liver tumors.

Is selective internal radiation therapy chemotherapy?

No. It delivers internal radiation through radioactive microspheres rather than delivering a chemotherapy drug.

Why is mapping required before SIRT?

Mapping identifies tumor-feeding and nontarget arteries, estimates potential lung exposure, and helps the treatment team plan microsphere delivery and radiation dose.

Can SIRT be repeated?

Yes. Repeat or staged treatment can be considered when the remaining liver reserve, tumor distribution, and previous radiation dose make another session appropriate.

References

ACR-ABS-ACNM-ASTRO-SIR-SNMMI practice parameter for selective internal radiation therapy or radioembolization for treatment of liver malignancies. PubMed. https://pubmed.ncbi.nlm.nih.gov/33824051/. Date Accessed September 11, 2026.

Advances and Emerging Techniques in Y-90 Radioembolization for Hepatocellular Carcinoma. PubMed. https://pubmed.ncbi.nlm.nih.gov/40361421/. Date Accessed September 11, 2026.

EANM procedure guideline for the treatment of liver cancer and liver metastases with intra-arterial radioactive compounds. PubMed. https://pubmed.ncbi.nlm.nih.gov/35146577/. Date Accessed September 11, 2026.

Recommendations for the management of yttrium-90 radioembolization in the treatment of patients with colorectal cancer liver metastases: a multidisciplinary review. PubMed. https://pubmed.ncbi.nlm.nih.gov/37747636/. Date Accessed September 11, 2026.

Yttrium-90 Selective Internal Radiation Therapy for Neuroendocrine Liver Metastases: An Institutional Case Series, Updated Systematic Review, and Meta-Analysis. PubMed. https://pubmed.ncbi.nlm.nih.gov/41515606/. Date Accessed September 11, 2026.