Radiofrequency Ablation of Malignant Liver Tumors
Radiofrequency ablation, also known as RFA, is an exciting,
recently developed technique used to treat malignant liver tumors. Radiofrequency ablation
uses electrical current, passed through a small needle placed directly into a liver tumor,
to destroy cancer cells with heat. The electrical current is actually passed across an
array of hook electrodes that are deployed from the tip of the needle after the needle is
placed into the tumor. The hook electrodes look like the ribs of an umbrella, with a
diameter of 3.5 cm (slightly greater than an inch) when fully deployed (figure 1). An
ultrasound probe is used to guide the placement of the needle into the tumors to be
treated, and after the needle is in the correct area, the hook electrodes are deployed
into the liver tumor. The treatment is started by applying electrical current from a
small, briefcase-sized device called a radiofrequency current generator. The amount of
power supplied by the generator can be controlled precisely, and the generator is also
used to monitor the treatment until complete heat-induced destruction of the tumor being
treated occurs.
Figure 1: RFA device
Radiofrequency ablation can be performed during an abdominal
operation, using laparoscopic surgical guidance (so-called minimally invasive surgery), or
by placing the needle through the skin directly into the tumor. The surgeons in the
Hepatobiliary Surgery section can explain the different approaches to each patient. In
general, most RFA procedures at the M.D. Anderson Cancer Center are performed during an
open abdominal operation, which allows the surgeon access to tumors at any site in the
liver. Laparoscopic or percutaneous (through the skin) RFA treatments are used most often
in patients with one to three small (less than 3.0 cm diameter) liver tumors located near
the surface of the liver. Patients with larger tumors, more numerous tumors (four to
eight), or with tumors located near large blood vessels within the liver are usually
treated during an open operation. Additionally, some patients are best treated by a
combination of removal of the largest liver tumors and RFA of any smaller tumors during
the same open operation. It is important to note that RFA performed laparoscopically or
through the skin still requires anesthesia so the patient will feel no pain or discomfort
during the treatment.
At the M.D. Anderson Cancer Center and at our collaborating
site, the G. Pascale National Cancer Institute in Naples, Italy, we have treated more than
320 patients with malignant liver tumors using RFA. This is by far the largest experience
in the world using RFA. Most of the patients were treated for colorectal cancer that had
spread (metastasized) to the liver or for primary liver cancer, also known as
hepatocellular cancer. However, we have treated patients with many other types of cancer
that spread to the liver, including breast, thyroid, islet cell, carcinoid, occular
melanoma, and gastrointestinal leiomyosarcoma. The key in each of these patients is that
the only site where cancer could be found was the liver, we do not perform RFA in patients
with cancer that has also spread to other areas or organs because treating only the liver
will not improve these patients’ chances for survival. We also have learned that it
is difficult, and probably not helpful, to treat patients with more than eight tumors or
if more than half of their liver is replaced by tumors. Lastly, we find that the RFA
equipment currently available does not reliably destroy all the tumor if it is larger than
6 cm in diameter, these larger tumors should be removed, when possible. Thus, we do not
recommend RFA for these larger liver tumors, but we, and others, are working to develop
RFA systems that will effectively treat larger tumors.
We have been very pleased with the results and low rate of side
effects in liver tumor patients treated with RFA. Less than 4% of our patients suffer any
serious side effects, such as infection, bile leakage from the liver, or breathing
difficulties. The rate of tumor recurring in an area treated with RFA is 9%, and most
recurrences were along the outer edges of tumors that we now know were too large to be
completely killed by RFA. We follow all patients closely after RFA treatment with blood
tests and either CT or MRI scans to observe for any evidence of recurrent cancer (figures
2 and 3). We have been treating liver tumor patients using RFA for over 4 years, and at
least half of the patients have developed new tumors, some in the liver and some at other
sites in the body. This indicates that tiny, or microscopic areas of tumor cells too small
to detect were present when the RFA treatment was performed. Occasionally, the new tumors
in the liver can also be treated with RFA. Because RFA only destroys the tumors we can
detect with ultrasound, CT, or MRI scans, new tumors may develop months or years after the
RFA treatment. For many types of tumors, we now use chemotherapy treatments for up to 6
months after the RFA procedure in an attempt to reduce the risk of new tumors developing.
We do have a significant number of patients who have not had tumors recur at the RFA or
other sites, however, we will continue to monitor all patients carefully for years to
come.
Figure 2: Before RFA
Figure 3: After RFA
RFA is a relatively new, but very exciting treatment for
patients with some types of malignant liver tumors. The treatments have been safe and well
tolerated in the overwhelming majority of patients. RFA has allowed us to treat patients
who previously would not have been considered for aggressive surgical treatments because
of the number of tumors, location of tumors too near major blood vessels, problems with
cirrhosis, or inability to remove the entire tumor while leaving behind enough normal
liver. At the University of Texas M.D. Anderson Cancer Center, we will continue to treat
patients using RFA, often in combination with other types of treatments, in hopes of
eradicating all of their malignant cells, and will continue to develop improved equipment
to treat larger tumors.
