| Radiofrequency Ablation of Liver Tumors
What is Radiofrequency Ablation of Liver Tumors? Back to Top
Many
methods of minimally invasive therapy have been tried in recent years
to eliminate tumors in organs like the liver. One of the most promising
is called radiofrequency ablation, sometimes referred to as RFA. A
special needle electrode is placed in the tumor under the guidance of
an imaging method such as ultrasound or computed tomography (CT)
scanning. A radiofrequency current then is passed through the electrode
to heat the tumor tissue near the needle tip and ablate—or
eliminate—it. The heat from radiofrequency energy also closes up small
blood vessels, thereby minimizing the risk of bleeding. In general,
radiofrequency ablation causes only minimal discomfort and may be done
as an outpatient procedure without general anesthesia. Admission to the
hospital is not usually necessary.
What are some common uses of the procedure? Back to Top
Two
types of liver tumor have been the main targets of radiofrequency
ablation: hepatocellular carcinoma, which is a primary liver cancer,
and colon cancer that spreads (metastasizes) to the liver. Many
patients with a malignant liver tumor are not good candidates for
surgery, sometimes because their tumor is too widespread or
inaccessible, or because of other medical conditions that make surgery
especially risky. In other cases, so much liver tissue would have to be
removed with the tumor that not enough would be left to provide
adequate liver function. For many of these patients, radiofrequency
ablation is a viable and effective treatment option.
Some liver tumors that have failed to respond to chemotherapy or
have recurred after initial surgery may be treated by radiofrequency
ablation. If there are multiple tumor nodules they may be treated in
one or more sessions. In some cases radiofrequency ablation has made it
possible to operate on a patient after eliminating several small liver
tumors that were too spread out to remove surgically. In general,
radiofrequency ablation is most effective if the tumor or tumors are
less than two inches in diameter. Although radiofrequency ablation can
be used to treat larger tumors, the results are not as good. Typically
radiofrequency ablation is not used to treat liver tumors if there is
active cancer outside of the liver.
How should I prepare for the procedure? Back to Top
You will
be asked to avoid food and liquids starting at midnight the evening
before treatment. Your doctor will tell you which medications you may
take in the morning. If you take aspirin, you may be instructed to stop
10 days beforehand. Consult your doctor if you are taking Coumadin or
another blood thinner. If your doctor does not plan to admit you to the
hospital overnight, you should arrive at the clinic with someone who
will drive you home afterwards.
What does the equipment look like? Back to Top
There are
three main components of the equipment needed for radiofrequency
ablation: needle electrodes, an electrical generator and grounding
pads. The needle electrodes come in two forms: simple straight needles
and straight needles that contain multiple curved, retractable
electrodes that are kept inside the needle until its tip is positioned
within a tumor. When properly positioned, a plunger on the hub of the
needle is advanced so that the electrodes extend from the needle tip.
When fully extended, these electrodes resemble an open umbrella or
Christmas tree. The radiofrequency generator is connected by insulated
wires to the needle electrodes and to grounding pads that are placed on
the patient's back or thigh. The generator produces alternating
electrical current in the range of radiofrequency waves.
How does the procedure work? Back to Top
Radiofrequency
ablation works by passing electrical current in the range of
radiofrequency waves between the needle electrode and the grounding
pads placed on the patient's skin. The current creates heat around the
electrode inside the tumor and this heat spreads out to destroy the
entire tumor but little of the surrounding normal liver tissue.
Basically the tumor is destroyed by "cooking" it. The tumor cells
exposed to the heat are killed immediately. Because healthy liver
tissue withstands more heat than a tumor, radiofrequency ablation is
able to destroy a tumor and a small rim of normal tissue about its
edges without affecting most of the normal liver. The dead tumor cells
are gradually replaced by scar tissue that shrinks over time.
How is the procedure performed? Back to Top
Radiofrequency
ablation may be done by placing ablation needles through the skin; by
placing needles through a tube inserted through small holes in the skin
(laparoscopy); or during open surgery. Most radiologists prefer the
percutaneous (through-the-skin) approach because it is much less
invasive, produces few complications and requires only sedation rather
than general anesthesia. In addition, as an outpatient procedure it is
relatively inexpensive. Radiofrequency ablation may be repeated as
needed should the tumor recur. An ultrasound probe may be used as a
"road map" to direct the radiofrequency needle to the correct position
on the abdominal surface to reach the tumor, and then to the center of
the tumor itself. Alternatively, CT imaging may serve the same purpose.
Local anesthetic is injected into the site where a quarter-inch skin
incision is planned, and the patient is sedated by an intravenous
injection. Once the needle electrode is in place, radiofrequency energy
is applied. For a larger tumor it may be necessary to do overlapping
ablations to make certain that no tumor tissue is left behind.
What will I experience during the procedure? Back to Top
Radiofrequency
ablation is generally done in a room devoted to CT or ultrasound
imaging. After you lie down on the examining table the tumor will be
located and you will receive intravenous sedation (through a tube
previously placed in an arm vein) to avoid discomfort during the
procedure. You may or may not remain awake, depending on how deeply you
are sedated. The skin area where the needle passes through will be
numbed with local anesthetic to further decrease discomfort. Each
radiofrequency ablation treatment takes about 12 to 30 minutes and the
total procedure will be completed in one to three hours, depending on
how many tumor sites have to be treated. After radiofrequency ablation
you may receive further medication to prevent pain and nausea as the
sedation wears off. Afterwards you will remain in the recovery room
until totally awake and ready to leave for home. Only about 2 percent
of patients will still have any degree of pain a week after
radiofrequency ablation.
Organs and tissues near the liver, such as the gallbladder, bile
ducts, diaphragm and bowel loops, are at risk of being injured. When
this happens, surgical correction may be necessary. This only happens 3
percent to 5 percent of the time, however, and this risk is related to
the location of the liver tumor that is treated.
Who interprets the results and how do I get them? Back to Top
Most
centers perform a CT or MRI scan of the liver within a few hours to a
week after radiofrequency ablation to make certain that all tumor
tissue has been destroyed, and also to detect any complications. A
radiologist will interpret the CT or MRI scans and determine whether
the entire liver tumor appears to have been eliminated. You will then
have repeat CT scans every three months to check for new tumors.
What are the benefits vs. risks? Back to Top
Benefits
- Radiofrequency ablation can be an effective treatment for
primary liver cancer or cancers that have spread to the liver in
selected patients whose disease is unsuitable for surgical resection.
- In most studies, more than half the liver tumors treated by radiofrequency ablation have not recurred.
- Treatment-related serious complications are infrequent.
- Radiofrequency ablation may be used repeatedly to treat recurrent liver tumors.
- Radiofrequency
ablation is a minimally invasive treatment that is rapidly completed
and often does not require hospital admission. Patients are usually
able to resume their usual activities within a few days. In addition,
radiofrequency ablation is less expensive than other treatment options.
Risks
- Depending on the site of treatment, radiofrequency
ablation may cause brief or, rarely, long-lasting shoulder pain;
inflammation of the gallbladder that subsides after a few weeks; damage
to the bile ducts resulting in biliary obstruction; or thermal damage
to the bowel.
- Roughly one in four patients may
develop a "post-ablation syndrome" with flu-like symptoms that appear
three to five days after the procedure and usually last about five
days. An occasional patient may remain ill for two to three weeks. Oral
acetaminophen commonly is given to control fever.
- Some
cases of bleeding have been reported but it usually stops on its own.
If bleeding is severe, an additional procedure or surgery may be needed
to control it.
What are the limitations of Radiofrequency Ablation of Liver Tumors? Back to Top
There
is a limit to the volume of tumor tissue that can be eliminated by
radiofrequency ablation. This is due to limitations in the size of the
"burn" that can be produced with current equipment. Hopefully technical
advances will permit larger tumors to be treated. Radiofrequency
ablation can destroy many small liver tumors but will not eliminate
microscopic-sized tumors and cannot prevent cancer from growing back. Back to Top |
