Embolization is the selective blocking of blood vessels by placing tiny particles in the vessel. Once the particles in place, the blood flow along that vessel is dimished or stopped entirely. Embolization is used for many purposes, such as cutting off the blood supply to malignant tumors or uterine fibroids, or to stop hemorrhaging in the lungs or nasal passages.
The particles are about the size of a grain of sand, and they are made of a plastic substance that is similar to the material used to make hard contact lenses, called polyvinyl alcohol (PVA). This is a medical-grade material that is FDA approved for embolization and has been used for embolization in the human body for over 20 years.
Embolization is a catheter-based procedure. The catheter is guided via fluoroscopy (live x-ray) to the location to be blocked. The particles are released until the blood flow has been reduced to the appropriate level. The catheter is withdrawn and the procedure is done.
Chemoembolization is a procedure in which chemotherapy drugs are delivered directly to a cancerous tumor, most often in the liver. In addition to the chemotherapy drugs, the blood vessels feeding the tumor are embolized, reducing the tumor’s ability to thrive.
During the procedure, an angiogram is performed so that the arteries that are supplying blood to the tumor can be identified. The chemotherapy drugs are then delivered into the artery so that they move directly to the tumor. After the drugs have been delivered, polyvinyl particles are released in the artery to further starve the tumor of oxygen and nutrients.
Chemoembolization has several benefits over traditional chemotherapy: the drugs are injected directly to the tumor and are more concentrated, the drugs continue to affect the tumors for up to a month, there are fewer side effects because the drugs do not circulate through the body, and the tumors are starved of oxygen and nutriets because the blood supply is compromised.
Chemoembolization is a procedure used to treat cancer—most often of the liver—using a combination of localized chemotherapy and embolization. It is a minimally invasive treatment that can be used when the tumor is too large to treat with radiofrequency ablation (RFA), the tumor is in a location that can’t be treated with RFA, or in combination with RFA and other treatments, such as surgery, chemotherapy or radiation therapy.
The liver is unique because it has two blood supplies—an artery (the hepatic artery) and a large vein (the portal vein). A normal liver receives about 75% of its blood supply through the portal vein and only 25% through the hepatic artery. But when a tumor grows in the liver, it receives almost all of its blood supply from the hepatic artery.
Chemoembolization attacks the cancer in two ways. First, high concentrations of chemotheraphy drugs are injected directly into the blood vessel that feeds a cancerous tumor. Then, using an X-ray for guidance, the interventional radiologist threads a tiny catheter up the femoral artery in the groin into the blood vessel feeding the tumor. A synthetic material called an embolic agent is placed inside the blood vessel, cutting off the blood supply, thus depriving the tumor of the oxygen and nutrients it needs to grow and, in effect, trapping the chemotherapy drugs in the tumor. This allows a higher dose of chemotherapy drugs to be used because less of the drugs are able to circulate to the healthy cells in the body.
Chemoembolization usually involves a hospital stay of two to four days. Patients typically have lower than normal energy levels for about a month afterward. It is a palliative, not curative, treatment. But it can be extremely effective in treating primary liver cancers, especially when combined with other therapies.
Chemoembolization is most beneficial to patients whose disease is mostly limited to the liver, whether the tumor began in there or metastasized (spread) from another organ.
Cancers that can be treated by chemoembolization include:
In about two-thirds of cases, chemoembolization stops liver tumors from growing or causes them to shrink. This benefit lasts for an average of 10 to 14 months, depending upon the type of tumor, and usually can be repeated if the cancer starts to grow again. Other types of therapy (e.g., tumor ablation, chemotherapy or radiation) can be used in combination with chemoembolization to control the tumor. When cancer is confined to the liver, most deaths are due to liver failure from the growing tumor, not due to the spread of cancer throughout the body. Chemoembolization can help prevent this growth, potentially preserving liver function and a relatively normal quality of life.
Any procedure that penetrates the skin carries a risk of infection. The chance of infection requiring antibiotic treatment is less than 1 in 1,000. Also, any procedure that involves placement of a catheter inside a blood vessel carries certain risks, including damage to the blood vessel, bruising or bleeding at the puncture site, and infection.
There is always a chance that embolization material can lodge in the wrong place and deprive normal tissue of its blood supply. There is a risk of infection after embolization, even if an antibiotic has been given. Because angiography is part of the procedure, there is a risk of an allergic reaction to the contrast material and kidney damage in patients with diabetes or other preexisting kidney disease.
Reactions to chemotherapy can include nausea, hair loss, a decrease in white blood cells, a decrease in platelets and anemia. Because chemoembolization traps most of the chemotherapy drugs in the liver, these reactions are usually mild.
Serious complications from chemoembolization occur after about 1 in 20 procedures. Most major complications involve either infection in the liver or damage to the liver. Reports indicate that approximately 1 in 100 procedures result in death, usually due to liver failure.
Chemoembolization is not recommended in cases where there is severe liver or kidney dysfunction, abnormal blood clotting, or a blocked bile duct. In some cases—despite liver dysfunction—chemoembolization can be performed in small amounts over several procedures to minimize the effect on the normal liver. Chemoembolization is a treatment, not a cure. Approximately 70% of patients will see improvement in the liver and, depending on the type of liver cancer, improved survival rates.