Mass General Hospital - Department of Radiology - Radiogrequency Ablation

WHAT IS RADIOFREQUENCY ABLATION (RFA)?
HOW RFA WORKS
CLINICAL APPLICATIONS OF RFA AND RESULTS
RFA TREATMENT RESULTS

WHAT IS RADIOFREQUENCY ABLATION (RFA)?

The standard methods for treating cancer of the liver and kidney are either surgery or chemotherapy. Recently, advances in minimally invasive techniques have been developed which can assist in treating these lesions. Most of the techniques developed are direct derivatives of basic needle biopsy procedures. That is, they involve placing a small (17 gauge) needle guided by ultrasound or CT into the tumor.
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Radiofrequency Ablation (RFA) is basically a derivative procedure from routine needle biopsy procedures that are performed by radiologists. RFA destroys tumor cells by heating them. While there are other methods of heating tumors, RFA, to date, is the most common of all thermal treatment methods. Over the last few years, developments in tumor ablation have allowed large volume tissue ablation to be performed safely on patients with either primary or metastatic liver disease, and, in selected patients with renal cell carcinoma. While other minimally invasive methods of tumor ablation have been used, at this point in time, RFA has been the most commonly used method.

HOW RFA WORKS

The procedure is usually performed under intravenous sedation (conscious sedation) on an outpatient basis. The patient is usually awake and is given standard drugs (midazolam, fentanyl, meperidine) to relax during the procedure. These are the same types of drugs that are given for any biopsy procedure. Most patients are comfortable during the procedure and require no pain medication or at the most, over- the-counter analgesics when at home.

A small needle (17 gauge) is inserted into the lesion using by ultrasound or CT guidance. The needle has an insulated portion and a variable length, uninsulated portion which is the heating element of the needle. A machine generates energy which is transmitted to the tip of the needle. The energy at the tip of the needle causes ionic agitation and frictional heat in the tissues surrounding the tip. In turn, these tissues can reach temperatures that cause cell death and coagulative necrosis. This usually occurs at temperatures above 50 degrees centigrade. The treatment can be repeated several times to kill more tissue. Each treatment takes about 15 minutes. Typically, RFA can create a kill area of 3-4 cm in size. The killed cells are not removed, but slowly are absorbed and digested by the natural "immune" system of the body, and a scar appears in the treated area.

Recently, microwave ablation systems have become available. These also allow special small needles to heat tissues causing cell death.

CLINICAL APPLICATIONS OF RFA AND RESULTS

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Liver tumors
In patients with liver tumors, local tumor control is possible, particularly in patients who are not ideal surgical candidates, have contraindications to surgery, have recurrent tumors, or have failed conventional therapies.

Primary Liver Tumors (Hepatoma, Hepatocellular Carcinoma)
RFA has proven most successful in the treatment of this type of tumor. In Italy, where this technique originated, RFA has replaced surgery as the treatment of choice. Because hepatomas are slow growing and often encapsulated, patients treated with RFA have shown excellent survival results.

Indications include patients who are potential candidates for RFA include those:

with tumors 5 cm in size or less (larger tumors can and have been treated, but these may require additional therapies)
with 3 or fewer tumors per patient (If there are more than 3 tumors, treatment with RFA can be performed, but it is less successful.)
patients who are waiting for a liver transplantation who have a hepatoma

Metastatic Disease to the Liver
The most common metastatic disease in the liver treated by RFA has been colon cancer. However, in selected cases, other types of tumors are amenable to treatment. Results with RFA are promising, but have not been as good as in primary tumors of the liver.

Indications include:

tumors < than 4 cm in size
no more than 3 tumors
no evidence of metastatic disease elsewhere

Radiofrequency ablation may also be helpful in patients who are undergoing surgery. For example, RFA may be combined with surgery to treat a patient who has several tumors in different locations. If RFA treatment is successful in one or two tumors, then surgery might be possible to resect another part of the liver which contains tumor. For example, a small tumor in the left lobe of the liver could be treated with RFA, and the tumor in the right lobe could be treated by surgical resection. RFA also can be used for treatment of tumor recurrence, as for example, in patients who have had surgical resection of a metastatic tumor that has a recurrence.

Kidney tumors
Similarly, RFA has shown promise in selected patients with kidney tumors. In most patients, surgery is the treatment of choice for kidney tumors; however, in in-patients with the following indications, RFA can be considered:

patients who have one kidney
patients with other medical conditions which might preclude surgery
elderly patients in whom surgery or post surgery recovery would be difficult
patients with tumors less than 5 cm in size, and which are peripheral in location

RFA TREATMENT RESULTS

Liver tumors
The world literature suggests that RFA is a safe and effective local treatment for neoplastic disease with a very low complication rate. Reported preliminary survival curves for small, solitary colorectal carcinoma (< 2cm) and hepatomas (< 3 - 4cm) are encouraging. Recent reports indicate that RFA results in complete necrosis of over 95 % of hepatomas of this size. In patients in whom there is some residual tumor, this area can be retreated. Results with colon carcinoma have shown with small lesions, results are close to those achieved with surgical resection.

Kidney Tumors
Experience with kidney tumors is considerably less than that with liver tumors. However, our early results would indicate that RFA is very effective for small (< 4 cm) exophytic tumors. Long-term survival data are not available but short-term results are promising.