context: Radioembolization is a cancer treatment in which radioactive particles are delivered to a tumor through the bloodstream. The particles lodge in the tumor and emit radiation that kills cancer cells. Radioembolization is most often used on cancers in the liver. Radioembolization is sometimes used for patients who may not be able to undergo other treatments. Experts are still determining its ideal uses. Radioembolization is performed during a procedure called an angiogram. A doctor first inserts a catheter into an artery in the groin. Under X-ray guidance, the catheter is moved into the blood vessels supplying the tumor in the liver. The doctor then injects liquid containing tiny radioactive particles into the proper artery (or arteries). The particles stay in the tumor, blocking blood flow to cancer cells, killing them, and shrinking the tumor. In most cases, the surrounding healthy liver suffers minimal radiation damage after radioembolization. The radiation in the particles gradually disappears over a month. The leftover particles can safely stay put forever. Prior to radioembolization, tests are performed in order to ensure safety and increase the likelihood of success. These include routine blood tests and an evaluation of blood flow, including an initial angiogram. The first angiogram serves as a test run, allowing a doctor to make sure the arteries of the abdomen and liver are suitable for radioembolization. Radioembolization is used primarily to treat cancer in the liver. The disease may take one of two forms: Cancer that has spread (metastasized) to the liver from a primary tumor elsewhere (such as colon or breast cancer) Cancer that first arises in the liver (such as hepatocellular carcinoma) Metastatic colorectal cancer in the liver and hepatocellular carcinoma are the cancers most often considered for radioembolization treatment. Radioembolization has also been used for other forms of cancer affecting the liver, such as: Cholangiocarcinoma Breast cancer or lung cancer with liver metastasis Neuroendocrine tumors, such as carcinoid tumors, that have spread to the liver A type of sarcoma called gastrointestinal stromal tumor ( GIST) Radioembolization is often used in coordination with more well-established cancer treatments, such as surgery and chemotherapy: Radioembolization may be used on liver tumors too large for surgery to shrink them to allow surgical removal. Chemotherapy and radioembolization may be provided in combination to maximize the destruction of cancer cells. Radioembolization can also be a treatment option for cancers in the liver that can't be removed surgically and are not responsive to chemotherapy. Through ongoing research, doctors are still determining the best uses of radioembolization. Radioembolization is generally only considered as treatment for cancers whose spread is limited to the liver. People with severe liver disease or abnormal blood flow between the liver and lungs are usually not eligible for radioembolization. In several small studies, radioembolization delayed progression of colorectal cancer after its spread to the liver. Radioembolization also has been shown to shrink hepatocellular carcinomas. So far there is a small amount of evidence that people who get radioembolization and chemotherapy for cancer in the liver live longer than people receiving chemotherapy only. Larger clinical trials are underway that should help answer questions about radioembolization's benefits. Many people experience symptoms of fatigue, nausea, abdominal pain, fever, and loss of appetite after radioembolization. These effects are usually mild or moderate, and most people leave the hospital within a day or two after the procedure. Radioembolization has a low rate of serious side effects. However, a small percentage of people have serious problems after radioembolization. Potential complications of radioembolization include: Severe ulcers in the stomach or small intestine Liver or gallbladder failure Dangerously low white blood cell count Radiation damage to the lungs Tests performed before radioembolization can reduce some of the risks of complications from the procedure.