Ablation for GISTs and Gastric Neuroendocrine Tumors (NETs)

If you have a GIST or gastric NET and are discussing treatment options, you may have heard about ablation. Your doctors may even recommend it as part of your treatment plan. While all this new information about ablation therapy can leave you feeling confused and overwhelmed, understanding how it works is very important. Not only will it help you stay on top of medical discussions, but it can also prepare you for what to expect during your treatment journey and make the whole experience a little less unnerving.

Ablation is a type of 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 cannot be removed surgically. Together with embolization, it is also known as a locoregional treatment or interventional procedure.

Ablation involves the use of chemicals or extreme heat or cold to kill cancer cells. Because this treatment often destroys some healthy tissue surrounding the tumor, it may not be the best choice for treating tumors that are located near vital structures, such as major blood vessels or ducts in the liver, other organs, or the surface of the liver called the capsule.

This treatment is typically performed by a trained specialist called an interventional radiologist in an interventional radiology suite or sometimes in an operating room. Regardless of the type of ablation therapy, your radiologist will first use an imaging technique, such as a computed tomography (CT) scan or ultrasound, to locate the GIST or NET and guide the insertion of a needle probe through the skin and into the tumor. These probes are connected via cords to a generator that supplies heat or cold.

For larger tumors, your radiologist may need to perform multiple ablations. This is done by repositioning the needle probe or placing multiple needles into different parts of the tumor, which ensures that no tumor tissue remains. Multiple tumors can also be treated at the same time.

The entire procedure typically lasts one to three hours. It can be done under general anesthesia (where you are in a deep sleep) or with conscious sedation (where you are awake, but sleepy and should not experience any pain). The area of your skin through which the needle probe is inserted is numbed with local anesthetic. At the end, your radiologist removes the needle probe and applies pressure to stop any bleeding. The opening in the skin is then covered with a dressing. It is typically an outpatient procedure.

There are a few types of ablation used in the treatment of metastatic GISTs and gastric NETs.

Radiofrequency ablation (RFA)

Radiofrequency ablation (RFA) is a minimally-invasive procedure that can destroy tumors, such as liver metastases of GISTs and gastric NETs. The needle probe is first inserted into the center of the tumor. Metal prongs are then projected out from the needle’s hollow core, penetrating and enveloping the tumor. Subsequently, high-energy radio waves are passed through the needle to its tip and prongs. This creates a small area of heat that kills the cancer cells in the liver (in a process called coagulative necrosis) and closes small blood vessels, which lowers the risk of bleeding. Bit by bit, the dead tumor cells are replaced by scar tissue that eventually shrinks.

RFA can be performed in various ways. It can be administered during open or laparoscopic surgery, or by inserting the needle through the skin (percutaneously). The latter is typically done under local anesthesia, which involves numbing the site of needle insertion in the skin.

RFA is best suited for relatively small metastatic tumors, especially those less than 3 cm in size. There mustn’t be too many of these tumors and they cannot be close to major blood vessels or ducts in the liver. Patients sometimes need several procedures to get rid of all of the lesions.

Microwave ablation (MWA)

Microwave ablation (MWA) works in a similar way to RFA, but instead of radio waves, microwaves are transmitted through the probe. This generates heat that burns the tumor and destroys the cancer cells.

Cryoablation

Cryoablation (or cryotherapy) uses extremely cold temperatures to destroy cancerous tissue. Using an imaging technique as guidance, your doctor inserts a thin, wand-like needle known as a cryoprobe through your skin and directly into the tumor. Argon or nitrogen gas is then pumped through a tube and into the cryoprobe, bringing the temperature of the tumor to extremely low levels. This freezes and destroys the tumor. Sometimes, this procedure requires the administration of general anesthesia, which puts you in a deep sleep so that you do not feel any pain.

If you are currently undergoing GIST or NET cancer treatment and are interested in exploring ablation therapy 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 ablation therapy is the right choice for an effective treatment outcome.