Selective internal radiation therapy

Selective Internal Radiation Therapy (SIRT), also known as radioembolization, is a form of radiation therapy used in oncology to treat cancer, particularly liver cancer. It involves the delivery of radiation directly to the tumor site via the bloodstream, minimizing exposure to healthy tissues. This article provides an overview of SIRT, including its principles, indications, procedure, and potential complications.

Principles

Selective Internal Radiation Therapy works on the principle of targeting tumors with high doses of radiation while sparing the surrounding healthy tissue. It utilizes microspheres filled with a radioactive isotope, commonly Yttrium-90 (Y-90), which are injected into the arteries feeding the tumor. These microspheres lodge in the tumor's vasculature and emit radiation locally, causing cell death in the tumor.

Indications

SIRT is primarily indicated for the treatment of unresectable primary or secondary liver cancers, such as hepatocellular carcinoma (HCC) and metastatic colorectal cancer to the liver. It is often considered when other treatments, such as surgery, chemotherapy, or external beam radiation therapy, are not viable options or have been exhausted.

Procedure

The SIRT procedure is performed by a specialized team, including an interventional radiologist. It involves several steps: 1. Assessment: Patients undergo a thorough evaluation, including imaging studies like MRI or CT scans, to determine the feasibility of SIRT. 2. Pre-treatment angiography: An angiogram is performed to map the blood supply to the liver and tumor, identifying and, if necessary, embolizing (blocking) arteries to prevent the microspheres from reaching non-target areas. 3. Dosimetry: Calculation of the appropriate dose of radiation to be delivered. 4. Treatment: The Y-90 microspheres are infused into the liver arteries feeding the tumor through a catheter placed in the femoral artery or radial artery. 5. Post-treatment monitoring: Patients are monitored for any immediate complications, with follow-up imaging to assess the treatment's effectiveness.

Complications

While SIRT is generally well-tolerated, it can have complications, including:

• Post-embolization syndrome: Symptoms include fever, nausea, pain, and fatigue.
• Radiation-induced liver disease (RILD): A rare but serious condition characterized by liver failure.
• Non-target embolization: Accidental radiation of non-target tissues, leading to ulcers or gastrointestinal bleeding.

Conclusion

Selective Internal Radiation Therapy offers a targeted approach to treating liver cancers, with the potential for significant tumor reduction and palliation of symptoms. However, careful patient selection and a multidisciplinary approach are crucial to optimize outcomes and minimize risks.