Introduction to RFA
Radiofrequency ablation (RFA) is an exciting approach to treating cancer within several organs of the body, including the liver, kidneys, lungs, and bone. While surgery to remove these tumors is often the preferred treatment, many patients have disease that is too widespread or other medical conditions that make surgery risky or difficult. In addition, other patients have tumors that have recurred or have not responded to conventional therapies. These are the patients that have been shown to benefit from RFA, which has grown safer and more effective in recent years.
The benefits of RFA include preserving uninvolved liver tissue, causing potentially fewer systemic complications and side-effects than chemotherapy, and avoiding the potential risk of major surgery.
During these procedures, a needle-like probe is inserted through the skin and into the organ containing the tumor being treated. This probe is used to generate heat within the tumor and it is this heat which produces destruction (necrosis) of the tumor. In most studies, more than half of the liver tumors treated by RFA do not recur. Most patients spend a night in the hospital for observation after RFA and many return to their usual activities within a few days.
How are Patients Selected?
Liver Cancer | Kidney Cancer | Lung Cancer
RFA has been used with success to treat primary liver cancer (otherwise known as hepatocellular carcinoma) and cancers that have spread to the liver from other places, such as colon cancer. Surgical resection of these tumors in carefully selected patients can lead to significant long-term survival but only a small percentage of these patients are candidates for surgery.
Despite the fact that the evolution of surgical technique has increased the numbers of patients considered candidates for surgery, there are still many patients with cancer involving the liver that can potentially benefit from a procedure such as RFA.
Patients with symptomatic neuroendocrine (carcinoid) tumors are also ones that can benefit from RFA. Carcinoid tumors often arise from the GI tract or lung and can then metastasize to the liver.
Even though these tumors tend to be slow-growing, they are often associated with significant symptoms relating to hormone production. These symptoms, known as the carcinoid syndrome, include flushing, palpitations, and diarrhea that can often be debilitating. Treating these tumors with local tumor therapy can relieve or reduce symptoms which can improve quality of life in these patients.
A consultation with one of the interventional radiologists of Interventional Care will help determine if a patient is a candidate for radiofrequency. This involves reviewing all imaging studies that the patient may have had during the course of their treatment with an oncologist in order to determine the extent of tumor involvement within the liver.
The ideal size of a lesion to be treated with RFA is <4 cm because larger tumors may recur due to incomplete necrosis of the tumor cells. However, patients with tumors up to 6 cm in diameter can be considered for RFA and for those patients, multiple overlapping ablations may need to be performed to increase our certainty that the entire tumor is treated.
We also tend to prefer that patients have three or fewer tumors in the liver in order to be considered for RFA since it is unlikely that patients with a greater number of lesions will realize a survival benefit from RFA. Patients with more tumors may be considered possible candidates for regional therapy such as chemoembolization and radioembolization with RF ablation considered in these patients if three or fewer lesions do not respond to that initial regional therapy.
Lesions deep within the liver tend to be more preferable to treat then lesions immediately under the surface of the liver since there tends to be slightly more post-procedure pain associated with RFA of lesions near the capsule or surface of the liver.
Finally, it is desirable to treat lesions with RFA that are not immediately adjacent to large blood vessels because blood flow near the tumor can potentially cool the tissue during the procedure and prevent a full ablation. This can put that patient at risk for tumor regrowth.
It is often said that therapies such as RF ablation should not be considered if extrahepatic metastatic disease has been found. We choose to not issue such broad statements and instead consider each patient individually in order to determine the relative severity of the intrahepatic and extrahepatic disease. In this way, if the presence of liver disease is felt to be placing a patient at risk for future liver failure, then we consider that patient to be a potential candidate for RF ablation if the other, above-mentioned criteria are met.
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Although surgery continues to remain the treatment of choice for most kidney tumors, some patients can potentially benefit from RFA. This includes patients with a high degree of surgical risk due to multiple medical problems, borderline kidney function, or one kidney. In addition, patients with multiple recurrent tumors (as seen in conditions such as Von-Hippel Lindau disease) can benefit from RFA.
Almost all tumors <3 cm and located on the outside or periphery of the kidney can be successfully treated with RFA. Tumors that are close to the collecting system of the kidney can potentially be treated with percutaneous cryoablation.
Before RFA of the kidney is performed, a complete urologic and imaging evaluation must be performed to be certain that the disease is confined to the kidney, with no extension into the blood vessels surrounding the kidney.
RFA is now considered to be an option for patients with primary lung cancer or metastatic disease involving the lung who wish to avoid conventional surgery or are too ill to undergo surgery due to advanced disease in the lungs or poor cardiac and/or pulmonary function.
In addition, RFA is not intended to replace surgery, radiation, or chemotherapy but can be helpful to some patients when used alone or in conjunction with these treatments. It is most often used to treat cancers that are limited in size (<3 cm in diameter) and are separate from vital structures in the chest.
RFA has also been used to successfully address the pain associated with masses involving the chest wall and to debulk tumors that are too large to remove surgically. Debulking may allow the remaining parts of the tumor to be treated with chemotherapy or radiation therapy.
Finally, RFA can be used to treat patients with recurrent disease after radiation therapy since these patients are often not candidates for surgery or additional courses of radiation.
What Equipment is Used?
There are three basic types of systems used for RF ablation procedures. The specific RFA system and guidance method are chosen based on location and size of the tumor to be treated, proximity of large vessels, bleeding risk, the pathway that the needle-electrode has to take to enter the tumor, and the importance of minimizing collateral damage.
The systems differ based on the length and configuration of the active tip of the needle-electrode. There are simple straight needles and straight needles that contain multiple curved, retractable electrodes that are kept inside the needle until the tip is positioned within the tumor.
In addition, some systems have cold water flowing through the electrode in order to avoid overcooking (or charring) of the tissue during the ablation procedure. All of the different needle-electrode systems connect to a radiofrequency generator and to grounding pads that are placed on the patient’s back or thighs.
The goal of RFA is to heat the tumor cells to temperatures greater than 60 degrees Celsius. At these temperatures, intracellular proteins and cell membranes are destroyed, killing tumor cells. This creates a region of necrosis surrounding the electrodes.
All of the different systems available are able to heat tissue to temperatures exceeding 100 degrees Celsius. Conductive heat is emitted from the treated tissue, which creates a zone of ablation around the tumor. The size of the ablation zone corresponds to the size of the probe used. Therefore, probes are selected based on the size of the tumor being treated.
New RFA probes are being developed to treat larger hepatic tumors. At this time, the largest zone of ablation we are able to create is 7 cm.
How is RFA Performed?
Before the procedure, you will be asked to have nothing to eat or drink starting at midnight the evening before treatment. Your list of medications will be reviewed with our staff at the time of your consultation and you will be told which medications you may take in the morning of the procedure.
If you are taking Coumadin, Plavix, or another blood thinner, you may need to stop taking that medication several days before the procedure.
The procedure itself is performed in a room containing a CT scanner or ultrasound machine, depending on which of these machines will be used for guidance during the procedure. You will be sedated through an IV line in your arm. Some patients may require the use of general anesthesia depending on their medical condition and anticipated discomfort during the procedure.
Before the procedure begins, patients are hydrated and given antibiotics to prevent procedure-related infections. Local anesthesia is injected into the skin surface and medicine for sedation is given to the patient through an IV.
Routine cardiovascular and respiratory monitoring helps ensure patient safety during the procedure. Grounding pads are placed on the thighs prior to beginning the procedure.
The procedure begins with a very small incision made in the skin. This allows a needle to be passed through the skin and into the organ containing the tumor. Ultimately, this needle is placed directly into the tumor being targeted for treatment. This is all done under the guidance of an imaging method such as ultrasound, CT, or MRI.
Once the needle is in place, a probe is passed through the needle into the tumor. This probe has many electrodes at its tip and these electrodes are projected into the tumor.
The probe is then attached to an RF generator and a current is passed through the probe in order to heat the tumor tissue. This heat spreads out around the electrodes and destroys the entire tumor, which takes approximately 15-20 minutes. For larger tumors, it is often necessary to perform overlapping ablations to be certain that the entire tumor is treated.
During the procedure, temperature is monitored so that the appropriate wattage and current may be applied to the tissue. When tumor cells are heated up in this manner, they die along with a small rim of normal tissue that surrounds them. More normal tissue is not destroyed because healthy liver is able to tolerate the heat better than the tumor can.
The dead tumor cells are gradually replaced by scar tissue that shrinks over time. If it happens at all, recurrent tumor tends to be found along the edge of the treated area of the liver, in which case retreatment is possible. That is why close follow-up with CT scans is very important.
What is the Success Rate?
Based on available data, outcomes appear to be excellent for patients with unresectable primary hepatocellular carcinoma. Reports show that well over 3,000 primary and metastatic liver tumors have been treated with RFA. These studies suggest that complete local response can be seen in 70-75% of patients with tumors ranging in diameter between 3 and 5 cm.
Patients with single primary liver tumors <3 cm in diameter and metastatic colorectal tumors <2 cm in diameter have a comparable survival rate after surgery or RFA. For patients with larger tumors, we worry about the risk of recurrent because larger tumors are more difficult to completely treat.
This seems to be reflected in the medical literature, with the risk of recurrence in patients with tumors >5.0 cm quoted as high as 75%. In these patients, recurrent or persistent tumor is usually at the periphery or margin of the tumor and this can be retreated if recognized.
With successful ablation, 5-year survival rates of 40-50% have been reported for primary liver cancer. This is why it is often said that patient selection has the greatest impact on disease-free survival after RFA.
While persistent tumor at the site of ablation is one concern after RFA, a second concern is the development of new areas of tumor that are remote from the treated area. This is more of a concern in patients with metastatic disease involving the liver but can also be seen in patients with primary liver cancer.
Studies have shown that 50% or more of patients with metastatic disease will have a new occurrence of intrahepatic or extrahepatic metastases. That is why close follow-up of these patients is recommended because once new lesions are able to be detected with imaging, they can be considered for treatment as well.
How Will I Feel After RFA?
After the procedure, you may receive additional medication to prevent pain and nausea as the sedation wears off. Almost all of our patients are admitted overnight after the procedure to make sure that any pain is addressed with medication and to be certain that there are no post-procedure complications. You will need someone to take you home on the morning after the procedure.
Once you arrive home, you can expect to have some mild post-procedure side effects. Most of these are due to the effects of the anesthesia used during the procedure and not to the procedure itself. These include mild flu-like symptoms with a low-grade fever and muscle aches. Additional symptoms include minor discomfort at the ablation site, which can be relieved with pain medication.
Some patients may develop a “post-ablation syndrome” which is related more to a tumor being treated than to the site of treatment. This may include flu-like symptoms and fever that tends to only last 3-5 days after the procedure. This is much less severe than the post-procedure symptoms seen after therapies such as chemoembolization.
What Else Should I Know?
What are the Possible Risks of Radiofrequency Ablation?
Procedure-related complications tend to be unusual after RFA and tend to be dependent on the part of the body being treated.
The risks of treating patients with liver disease include bleeding around the liver (subcapsular hematoma), fluid collection around the lung (pleural effusion), fluid collection around the liver (ascites), obstruction of the bile ducts within the liver, inflammation of the gallbladder, shoulder pain due to inflammation of the diaphragm, and infection with possible abscess formation. Serum liver function tests tend to be elevated for several days following the treatment of liver lesions but for most patients, these lab values return to baseline within a week.
The risks of treating patients with kidney disease include bleeding around the kidney, obstruction to urine flow from the treated kidney, and reduced function or the treated kidney.
The risks of treating patients with lung disease include bleeding within and around the lung and collapse of lung (pneumothorax) due to air leaking around the needle and entering the space surrounding the lung.
While many of these complications can be observed without additional treatment, some may require additional procedures for treatment.
How do we follow Patients after Radiofrequency Ablation?
After RFA, all patients require follow-up imaging on a regular basis to determine if the treated lesions have grown or if new lesions have developed.
We typically perform a CT scan in 1 month, which then serves as our new “baseline” for future imaging. CT scans are then performed at 3 month intervals for 1 year. If the disease is stable at that point, this changes to performing CT scans at 6 month intervals.
Initially, tumors after RFA may appear larger than they did before the procedure. That is because the tumor and the liver tissue immediately surrounding the tumor are addressed with RFA.
In some patients, the post-treatment inflammatory changes surrounding the treated tumor may be difficult, if not impossible, to differentiate from recurrent or incompletely treated tumor. Time is often the only way to make this differentiation.
Concern arises when continued growth is seen within the area treated with RFA and if that is seen, additional treatment will need to be considered. Typically, areas treated completely result in necrotic changes that shrinks over the course of several months.