Embolization for GISTs and Gastric Neuroendocrine Tumors (NETs)

When faced with a diagnosis of GIST or gastric NET, it can be overwhelming to consider the various options available for treatment. One such option that your doctors may recommend is embolization. The process of embolization can seem intimidating but understanding how it works is crucial in making informed decisions about your treatment plan, improving your chances of a successful outcome.

Embolization is a liver-directed treatment used for GISTs and gastric NETs that, despite treatment with other therapies, have spread to the liver as a few tiny tumors and if surgery cannot be done to remove these tumors. Together with ablation therapy, it is also known as a locoregional treatment or interventional procedure.

Embolization involves the injection of substances into your blood vessels to stop or reduce the blood supply to cancer cells in the liver. This starves the tumor of oxygen and nutrients, which are delivered via the blood vessels, thereby destroying the cancer cells.

The liver is unique in that it has a dual blood supply. While most healthy liver cells receive their blood supply from branches of the portal vein, cancer cells in the liver are typically supplied by branches of the hepatic artery. In fact, the hepatic artery provides a GIST or NET with more than 90 percent of its blood supply. By blocking branches of the hepatic artery that feed the tumor, embolization is able to kill cancer cells in the liver while leaving most healthy liver cells unharmed.

Embolization is commonly used for larger tumors located deep in the liver, where your surgeon is unable to remove the tumors without risking the liver’s blood supply. It should be noted that embolization can lower some of the blood flow to normal liver tissue, so it might not be a good treatment option if your liver has been damaged by conditions such as hepatitis or cirrhosis.

Please be rest assured that follow-up imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI) scans, are performed to examine your response to these embolization procedures and to monitor the treated tissues over time.

There are three types of embolization used in the treatment of metastatic GISTs and gastric NETs.

Transarterial embolization (TAE)

Transarterial embolization (TAE) is the most common type of embolization used to treat tumors that have spread to the liver. It is also known as hepatic artery embolization (HAE) or bland embolization.

During this minimally-invasive procedure, a thin, flexible tube called a catheter is inserted into an artery through a small cut in the inner thigh and threaded up into the hepatic artery in your liver. A dye is typically injected into your bloodstream at this time, allowing your radiologist to observe the path of the catheter via a special type of X-ray called an angiography and guide its insertion into the hepatic artery.

Once the catheter is securely in place, microscopic particles composed of gelatin sponges or beads are injected into the hepatic artery or one of its branches to plug it up. These substances, which are known as embolic agents, block the blood supply to the liver tumor and kill the cancer cells. This subsequently leads to shrinkage or necrosis of the tumor.

What happens to the plug depends on the type of embolic agents used. Some embolic agents are designed to gradually break down and/or be absorbed by your body. Others, especially those that are not biodegradable or bioresorbable, may remain in the treated area. Known as permanent embolics, these agents can become encapsulated by scar tissue, incorporated into nearby tissues or carried away to smaller vessels where they are lodged.

The use of permanent embolics in TAE is generally considered safe and effective when performed by trained and experienced interventional radiologists. However, as with any medical procedure, there are potential risks and complications associated with TAE using permanent embolics. These include:

• Ischemia: If the embolization is too extensive, it could potentially lead to damage of healthy tissue due to ischemia (lack of blood supply).
• Reperfusion injury: In some cases of TAE, blood flow may be restored after a certain period of ischemia. This can lead to inflammation and additional tissue damage, known as reperfusion injury.
• Non-target embolization: There is a risk of embolic material traveling to other areas and causing blockages in vessels that are not intended for treatment. This could potentially affect healthy liver tissue and liver function.

More common side effects are pain and nausea after the treatment which is usually self-limited. Therefore, it is vital that you discuss the potential risks and benefits of TAE with your doctors before opting for the procedure.

Transarterial chemoembolization (TACE)

Transarterial chemoembolization (TACE), also known as hepatic artery chemoembolization (HACE), works in a similar way to TAE. However, microspheres coated with chemotherapy drugs are injected into the hepatic artery just before it is plugged with an embolic agent.

Besides stopping the tumor’s blood supply, this procedure delivers a very high concentration of chemotherapeutic agents to the tumor, which can help to destroy the cancer cells directly. The injection of embolic agents also traps the chemotherapeutics in the tumor, allowing their cancer-killing effects to last for a prolonged period of time.

Transarterial radioembolization (TARE)

Transarterial radioembolization (TARE) is a minimally-invasive procedure that combines embolization and radiotherapy to treat GISTs and NETs that have spread to the liver. It works similarly to TACE, but instead of microspheres coated with chemotherapy agents, tiny radioactive spheres are injected into the hepatic artery. This blocks the supply of blood to the tumor and delivers a high dose of radiation to the tumor in the liver, thereby killing the cancer cells.

If you are currently undergoing gastric cancer treatment and are interested in exploring embolization as a potential option, don’t hesitate to approach your cancer care team. Your doctors and cancer care team can provide you with detailed information about the procedure and whether it is an appropriate option. By working together, you can make an informed decision on whether embolization is the right choice for an effective treatment outcome.