Selective Internal Radiation Therapy (SIRT), also known as radioembolization, is a minimally invasive treatment for liver cancer. It is primarily used for treating primary liver cancer (hepatocellular carcinoma) or liver metastases from colorectal cancer. SIRT is a form of targeted radiation therapy that delivers radiation directly to the tumor in the liver while sparing normal liver tissue.
Here's how SIRT works:
- Microspheres with Radioactive Material: Small radioactive beads or microspheres, usually containing the radioisotope yttrium-90 (Y-90), are injected into the blood vessels that supply the liver tumors. Yttrium-90 emits beta radiation, which has a short range, allowing it to target the cancer cells while minimizing damage to nearby healthy liver tissue.
- Blood Supply to Tumors: The liver tumors receive a significant portion of their blood supply from the hepatic artery. SIRT takes advantage of this by delivering the radioactive microspheres directly into the hepatic artery, where they become lodged in the small blood vessels that feed the tumors.
- Local Radiation Effect: Once lodged in the blood vessels near the tumor, the radioactive microspheres emit radiation, damaging the cancer cells. The short range of the beta radiation helps confine the radiation effects to the tumors, minimizing damage to the surrounding healthy liver tissue.
- Tumor Shrinkage: The radiation damages the cancer cells, leading to tumor shrinkage and, in some cases, the destruction of the tumor.
SIRT is usually considered when other treatment options, such as surgery or ablation, are not feasible. It may be used as a primary treatment or in conjunction with other therapies, such as chemotherapy or surgery. It is important to note that SIRT is not suitable for all patients, and the decision to undergo this treatment depends on various factors, including the size and location of the tumors, the overall health of the patient, and the extent of liver disease.